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Optical experiment showing Fourier telescope and lasers

by Chris Woodford . Last updated: January 6, 2023.

Photo: There are always new theories to test and experiments to try. Even when we've completely nailed how Earth works, there's still the rest of the Universe to explore! Fourier telescope experiment photo by courtesy of NASA .

1: Galileo demonstrates that objects fall at the same speed (1589)

Photo: Galileo proved that different things fall at the same speed.

2: Isaac Newton splits white light into colors (1672)

Artwork: A glass prism splits white light into a spectrum. Nature recreates Newton's famous experiment whenever you see a rainbow!

3: Henry Cavendish weighs the world (1798)

Artwork: Henry Cavendish's experiment seen from above. 1) Two small balls, connected by a stick, are suspended by a thread so they're free to rotate. 2) The balls are attracted by two much larger (more massive) balls, fixed in place. 3) A light beam shines from the side at a mirror (green), mounted so it moves with the small balls. The beam is reflected back onto a measuring scale. 4) As the two sets of balls attract, the mirror pivots, shifting the reflected beam along the scale, so allowing the movement to be measured.

4: Thomas Young proves light is a wave... or does he? (1803)

Artwork: Thomas Young's famous double-slit experiment proved that light behaved like a wave—at least, some of the time. Left: A laser (1) produces coherent (regular, in-step) light (2) that passes through a pair of slits (3) onto a screen (4). If Newton were completely correct, we'd expect to see a single bright area on the screen and darkness either side. What we actually see is shown on the right. Light appears to ripple out in waves from the two slits (5), producing a distinctive interference pattern of light and dark areas (6).

5: James Prescott Joule demonstrates the conservation of energy (1840)

Artwork: The "Mechanical Equivalent of Heat"—James Prescott Joule's famous experiment proving the law now known as the conservation of energy.

6: Hippolyte Fizeau measures the speed of light (1851)

Artwork: How Fizeau measured the speed of light.

7: Robert Millikan measures the charge on the electron (1909)

Artwork: How Millikan measured the charge on the electron. 1) Oil drops (yellow) are squirted into the experimental apparatus, which has a large positive plate (blue) on top and a large negative plate (red) beneath. 2) X rays (green) are fired in. 3) The X rays give the oil drops a negative electrical charge. 4) The negatively charged drops can be made to "float" in between the two plates so their weight (red) is exactly balanced by the upward electrical pull of the positive plate (blue). When these two forces are equal, we can easily calculate the charge on the drops, which is always a whole number multiple of the basic charge on the electron.

8: Ernest Rutherford (and associates) split the atom (1897–1932)

Artwork: Transmutation: When Rutherford fired alpha particles (helium nuclei) at nitrogen, he produced oxygen. As he later wrote: "We must conclude that the nitrogen atom is disintegrated under the intense forces developed in a close collision with a swift alpha particle, and that the hydrogen atom which is liberated formed a constituent part of the nitrogen nucleus." In other words, he had split one atom apart to make another one.

Artwork: In Rutherford's gold-foil experiment (also known as the Geiger-Marsden experiment), atoms in a sheet of gold foil (1) allow positively charged alpha particles to pass through them (2) as long as the particles are traveling clear of the nucleus. Any particles fired at the nucleus are deflected by its positive charge (3). Fired at exactly the right angle, they will bounce right back! While this experiment is not splitting any atoms, as such, it was a key part of the decades-long effort to understand what atoms are made of—and in that sense, it did help physicists to "split" (venture inside) the atom.

9: Enrico Fermi demonstrates the nuclear chain reaction (1942)

Artwork: The nuclear chain reaction that turns uranium-235 into uranium-236 with a huge release of energy.

10: Rosalind Franklin photographs DNA with X rays (1953)

Artwork: The double-helix structure of DNA. Photographed with X rays, these intertwined curves appear as an X shape. Studying the X pattern in one of Franklin's photos was an important clue that tipped off Crick and Watson about the double helix.

If you liked this article...

Find out more, on this website.

  • Six Easy Pieces by Richard Feynman. Basic Books, 2011. This book isn't half as "easy" as the title suggests, but it does contain interesting introductions to some of the topics covered here, including the conservation of energy, the double-slit experiment, and quantum theory.
  • The Oxford Handbook of the History of Physics by Jed Z. Buchwald and Robert Fox (eds). Oxford University Press, 2013/2017. A collection of twenty nine scholarly essays charting the history of physics from Galileo's gravity to the age of silicon chips.
  • Great Experiments in Physics: Firsthand Accounts from Galileo to Einstein Edited by Maurice Shamos. Dover, 1959/1987. This is one of my favorite science books, ever. It's a great compilation of some classic physics experiments (including four of those listed here—the experiments by Henry Cavendish, Thomas Young, James Joule, and Robert Millikan) written by the experimenters themselves. A rare opportunity to read firsthand accounts of first-rate science!

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Observations

Which Should Come First in Physics: Theory or Experiment?

Plans for giant particle accelerators of the future focus attention on how scientific discoveries are really made  

  • By Grigoris Panoutsopoulos , Frank Zimmermann  on  June 17, 2019

Which Should Come First in Physics: Theory or Experiment?

The discovery of the Higgs particle at the Large Hadron Collider (LHC) over half a decade ago marked a milestone in the long journey toward understanding the deeper structure of matter. Today, particle physics strives to push a diverse range of experimental approaches from which we may glean new answers to fundamental questions regarding the creation of the universe and the nature of the mysterious and elusive dark matter.

Such an endeavor requires a post-LHC particle collider with an energy capability significantly greater than that of previous colliders. This is how the idea for the Future Circular Collider (FCC) at CERN came to be—a machine that could put the exploration of new physics in high gear. To understand the validity of this proposal, we should, however, start at the beginning and once more ask ourselves: How does physics progress?

Many believe that grand revolutions are driven exclusively by new theories, whereas experiments play the parts of movie extras. The played-out story goes a little something like this: theorists form conjectures, and experiments are used solely for the purposes of testing them. After all, most of us proclaim our admiration for Einstein’s relativity or for quantum mechanics, but seldom do we pause and consider whether these awe-inspiring theories could have been attained without the contributions of the Michelson-Morley, Stern-Gerlach or black-body radiation experiments.

This simplistic picture, despite being far removed from the creative, and often surprising, ways in which physics has developed over time, remains quite widespread even among scientists. Its pernicious influence can be seen in the discussion of future facilities like the proposed FCC at CERN.

In the wake of the discovery of the Higgs boson in 2012, we have finally of all of the pieces of puzzle of the Standard Model (SM) of physics in place. Nevertheless, the unknowns regarding dark matter, neutrino masses and the observed imbalance between matter and antimatter are among numerous indications that the SM is not the ultimate theory of elementary particles and their interactions.

Quite a number of theories have been developed to overcome the problems surrounding the SM, but so far none has been experimentally verified. This fact has left the world of physics brimming with anticipation. In the end, science has shown time and again that it can find new, creative ways to surmount any obstacles placed along its path. And one such way is for experimentation to assume the leading role, so that it can help get the stuck wagon of particle physics moving and out of the mire.

In this regard, the FCC study was launched by CERN in 2013 as a global effort to explore different scenarios for particle colliders that could inaugurate the post-LHC era and for advancing key technologies. A staged approach, it entails the construction of an electron-positron collider followed by a proton collider, which would present an eightfold energy leap compared to the LHC and thus grant us direct access to a previously unexplored regime. Both colliders will be housed in a new 100-kilometer circumference tunnel. The FCC study complements previous design studies for linear colliders in Europe and Japan, while China also has similar plans for a large-scale circular collider.

Future colliders could offer a deep understanding of the Higgs properties, but even more importantly, they represent an opportunity for exploring uncharted territory in an unprecedented energy scale. As Gian Giudice, head of CERN's Theoretical Physics Department, argues: “High-energy colliders remain an indispensable and irreplaceable tool to continue our exploration of the inner workings of the universe.”

Nevertheless, the FCC is seen by some as a questionable scientific investment in the absence of clear theoretical guidance about where the elusive new physics may lie. The history of physics, however, offers evidence in support of a different view: that experiments often play a leading and exploratory role in the progress of science.

As the eminent historian of physics Peter Galison puts it, we have to “step down from the aristocratic view of physics that treats the discipline as if all interesting questions are structured by high theory.” Besides, quite a few experiments have been realized without being guided by a well-established theory but were instead undertaken for the purposes of exploring new domains. Let us examine some illuminating examples.

In the 16th century, King Frederick II of Denmark financed Uraniborg , an early research center, where Tycho Brahe constructed large astronomical instruments, like a huge mural quadrant (unfortunately, the telescope was invented a few years later) and carried out many detailed observations that had not previously been possible. The realization of an enormous experimental structure, at a hitherto unprecedented scale, transformed our view of the world. Tycho Brahe’s precise astronomical measurements enabled Johannes Kepler to develop his laws of planetary motion and to make a significant contribution to the scientific revolution.

The development of electromagnetism serves as another apt example: many electrical phenomena were discovered by physicists such as Charles Dufay, André-Marie Ampère and Michael Faraday in the 18th and 19th centuries through experiments that had not been guided by any developed theory of electricity.

Moving closer to the present day, we see that the entire history of particle physics is indeed full of similar cases. In the aftermath of World War II, a constant and laborious experimental effort characterized the field of particle physics, and it was what allowed the Standard Model to emerge through a “zoo” of newly discovered particles. As a prominent example, quarks, the fundamental constituents of the proton and neutron, were discovered through a number of exploratory experiments during the late 1960s at the Stanford Linear Accelerator.

The majority of practicing physicists recognize the exceptional importance of experiment as an exploratory process. For instance, Victor “Viki” Weisskopf, the former director-general of CERN and an icon of modern physics, grasped clearly the dynamics of the experimental process in the context of particle physics:

“There are three kinds of physicists, namely the machine builders, the experimental physicists, and the theoretical physicists. If we compare those three classes, we find that the machine builders are the most important ones, because if they were not there, we would not get into this small-scale region of space. If we compare this with the discovery of America, the machine builders correspond to captains and ship builders who truly developed the techniques at that time. The experimentalists were those fellows on the ships who sailed to the other side of the world and then jumped upon the new islands and wrote down what they saw. The theoretical physicists are those fellows who stayed behind in Madrid and told Columbus that he was going to land in India.” ( Weisskopf 1977 )

Despite being a theoretical physicist himself, he was able to recognize the exploratory character of experimentation in particle physics. Thus, his words eerily foreshadow the present era. As one of the most respected theoretical physicists of our time, Nima Arkani-Hamed, claimed in a recent interview , “when theorists are more confused, it’s the time for more, not less experiments.”

The FCC, at present, strives to keep alive the exploratory spirit of the previous fabled colliders. It is not intended to be used as a verification tool for a specific theory but as a means of paving multiple experimental paths for the future. The experimental process should be allowed to develop its own momentum. This does not mean that experimentation and instrumentation should not maintain a close relationship with the theoretical community; at the end of the day, there is but one physics, and it must ensure its unity.

The views expressed are those of the author(s) and are not necessarily those of Scientific American.

physics is experiments

ABOUT THE AUTHOR(S)

Grigoris Panoutsopoulos is a physicist and a historian of science. He is a Ph.D. candidate at the University of Athens; his research has focused on the history of CERN.

Frank Zimmermann is a senior accelerator scientist at CERN and the deputy leader of the Future Circular Collider Study. He is also a fellow of the American Physical Society and serves as the editor of the journal Physical Review Accelerators and Beams .

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Book cover

Physics Education pp 269–296 Cite as

Experiments in Physics Teaching

  • Raimund Girwidz 4 ,
  • Heike Theyßen 5 &
  • Ralf Widenhorn 6  
  • First Online: 12 January 2022

1039 Accesses

Part of the Challenges in Physics Education book series (CPE)

Experiments are an integral part of physics research and physics instruction. In physics research, an experiment is a reproducible empirical procedure for acquiring knowledge. Experimental physicists use experiments to gather empirical evidence by developing research questions, and designing and conducting appropriate experiments to answer these questions (see Chap. 1 ). They control and systematically alter parameters during data collection. An experiment requires comprehensive planning, precise data acquisition, analysis of the experimental data and their interpretation in the context of a theoretical framework. In research, the experiment primarily serves as a method to test assumptions about the outcomes of the experiment (hypotheses) in order to generate new insight and evidence (more differentiated considerations on the procedure and significance of experimentation in physics research are discussed in Chap. 5 ). In physics education, the experiment has many additional and different functions and serves a variety of goals. Teachers can use experiments as tools to convey new content knowledge, for example, by demonstrating a physics phenomenon or by investigating laws of physics quantitatively. In addition, experiments can be used to support students in learning experimentation as a fundamental method to establish and verify knowledge and to offer insights into processes of scientific inquiry. Furthermore, experimentation as a method has to be discussed in the context of nature of science knowledge and nature of scientific inquiry , which is discussed in detail in Chap. 5 . Physics teachers should know and be able to use the various functions of experimental activities in physics learning. In this chapter, we highlight the diversity of experimental approaches in physics instruction, their different goals (see Sect.  10.1 ) and their designs (see Sect.  10.2 ). Finally, we present recommendations for teaching from multiple instructional perspectives, including related psychological and pedagogical aspects (see Sect.  10.3 ).

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Acknowledgements

We would like to thank Lori Shabaan (Liberty High School, Hillsboro, USA) and Claudia von Aufschnaiter (University of Gießen, Germany), for carefully and critically reviewing this chapter.

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Girwidz, R., Theyßen, H., Widenhorn, R. (2021). Experiments in Physics Teaching. In: Fischer, H.E., Girwidz, R. (eds) Physics Education. Challenges in Physics Education. Springer, Cham. https://doi.org/10.1007/978-3-030-87391-2_10

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  • 1.1 Physics: An Introduction
  • Introduction to Science and the Realm of Physics, Physical Quantities, and Units
  • 1.2 Physical Quantities and Units
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  • Introduction to Uniform Circular Motion and Gravitation
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  • Introduction to Work, Energy, and Energy Resources
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  • 14.6 Convection
  • 14.7 Radiation
  • Introduction to Thermodynamics
  • 15.1 The First Law of Thermodynamics
  • 15.2 The First Law of Thermodynamics and Some Simple Processes
  • 15.3 Introduction to the Second Law of Thermodynamics: Heat Engines and Their Efficiency
  • 15.4 Carnot’s Perfect Heat Engine: The Second Law of Thermodynamics Restated
  • 15.5 Applications of Thermodynamics: Heat Pumps and Refrigerators
  • 15.6 Entropy and the Second Law of Thermodynamics: Disorder and the Unavailability of Energy
  • 15.7 Statistical Interpretation of Entropy and the Second Law of Thermodynamics: The Underlying Explanation
  • Introduction to Oscillatory Motion and Waves
  • 16.1 Hooke’s Law: Stress and Strain Revisited
  • 16.2 Period and Frequency in Oscillations
  • 16.3 Simple Harmonic Motion: A Special Periodic Motion
  • 16.4 The Simple Pendulum
  • 16.5 Energy and the Simple Harmonic Oscillator
  • 16.6 Uniform Circular Motion and Simple Harmonic Motion
  • 16.7 Damped Harmonic Motion
  • 16.8 Forced Oscillations and Resonance
  • 16.10 Superposition and Interference
  • 16.11 Energy in Waves: Intensity
  • Introduction to the Physics of Hearing
  • 17.2 Speed of Sound, Frequency, and Wavelength
  • 17.3 Sound Intensity and Sound Level
  • 17.4 Doppler Effect and Sonic Booms
  • 17.5 Sound Interference and Resonance: Standing Waves in Air Columns
  • 17.6 Hearing
  • 17.7 Ultrasound
  • Introduction to Electric Charge and Electric Field
  • 18.1 Static Electricity and Charge: Conservation of Charge
  • 18.2 Conductors and Insulators
  • 18.3 Coulomb’s Law
  • 18.4 Electric Field: Concept of a Field Revisited
  • 18.5 Electric Field Lines: Multiple Charges
  • 18.6 Electric Forces in Biology
  • 18.7 Conductors and Electric Fields in Static Equilibrium
  • 18.8 Applications of Electrostatics
  • Introduction to Electric Potential and Electric Energy
  • 19.1 Electric Potential Energy: Potential Difference
  • 19.2 Electric Potential in a Uniform Electric Field
  • 19.3 Electrical Potential Due to a Point Charge
  • 19.4 Equipotential Lines
  • 19.5 Capacitors and Dielectrics
  • 19.6 Capacitors in Series and Parallel
  • 19.7 Energy Stored in Capacitors
  • Introduction to Electric Current, Resistance, and Ohm's Law
  • 20.1 Current
  • 20.2 Ohm’s Law: Resistance and Simple Circuits
  • 20.3 Resistance and Resistivity
  • 20.4 Electric Power and Energy
  • 20.5 Alternating Current versus Direct Current
  • 20.6 Electric Hazards and the Human Body
  • 20.7 Nerve Conduction–Electrocardiograms
  • Introduction to Circuits and DC Instruments
  • 21.1 Resistors in Series and Parallel
  • 21.2 Electromotive Force: Terminal Voltage
  • 21.3 Kirchhoff’s Rules
  • 21.4 DC Voltmeters and Ammeters
  • 21.5 Null Measurements
  • 21.6 DC Circuits Containing Resistors and Capacitors
  • Introduction to Magnetism
  • 22.1 Magnets
  • 22.2 Ferromagnets and Electromagnets
  • 22.3 Magnetic Fields and Magnetic Field Lines
  • 22.4 Magnetic Field Strength: Force on a Moving Charge in a Magnetic Field
  • 22.5 Force on a Moving Charge in a Magnetic Field: Examples and Applications
  • 22.6 The Hall Effect
  • 22.7 Magnetic Force on a Current-Carrying Conductor
  • 22.8 Torque on a Current Loop: Motors and Meters
  • 22.9 Magnetic Fields Produced by Currents: Ampere’s Law
  • 22.10 Magnetic Force between Two Parallel Conductors
  • 22.11 More Applications of Magnetism
  • Introduction to Electromagnetic Induction, AC Circuits and Electrical Technologies
  • 23.1 Induced Emf and Magnetic Flux
  • 23.2 Faraday’s Law of Induction: Lenz’s Law
  • 23.3 Motional Emf
  • 23.4 Eddy Currents and Magnetic Damping
  • 23.5 Electric Generators
  • 23.6 Back Emf
  • 23.7 Transformers
  • 23.8 Electrical Safety: Systems and Devices
  • 23.9 Inductance
  • 23.10 RL Circuits
  • 23.11 Reactance, Inductive and Capacitive
  • 23.12 RLC Series AC Circuits
  • Introduction to Electromagnetic Waves
  • 24.1 Maxwell’s Equations: Electromagnetic Waves Predicted and Observed
  • 24.2 Production of Electromagnetic Waves
  • 24.3 The Electromagnetic Spectrum
  • 24.4 Energy in Electromagnetic Waves
  • Introduction to Geometric Optics
  • 25.1 The Ray Aspect of Light
  • 25.2 The Law of Reflection
  • 25.3 The Law of Refraction
  • 25.4 Total Internal Reflection
  • 25.5 Dispersion: The Rainbow and Prisms
  • 25.6 Image Formation by Lenses
  • 25.7 Image Formation by Mirrors
  • Introduction to Vision and Optical Instruments
  • 26.1 Physics of the Eye
  • 26.2 Vision Correction
  • 26.3 Color and Color Vision
  • 26.4 Microscopes
  • 26.5 Telescopes
  • 26.6 Aberrations
  • Introduction to Wave Optics
  • 27.1 The Wave Aspect of Light: Interference
  • 27.2 Huygens's Principle: Diffraction
  • 27.3 Young’s Double Slit Experiment
  • 27.4 Multiple Slit Diffraction
  • 27.5 Single Slit Diffraction
  • 27.6 Limits of Resolution: The Rayleigh Criterion
  • 27.7 Thin Film Interference
  • 27.8 Polarization
  • 27.9 *Extended Topic* Microscopy Enhanced by the Wave Characteristics of Light
  • Introduction to Special Relativity
  • 28.1 Einstein’s Postulates
  • 28.2 Simultaneity And Time Dilation
  • 28.3 Length Contraction
  • 28.4 Relativistic Addition of Velocities
  • 28.5 Relativistic Momentum
  • 28.6 Relativistic Energy
  • Introduction to Quantum Physics
  • 29.1 Quantization of Energy
  • 29.2 The Photoelectric Effect
  • 29.3 Photon Energies and the Electromagnetic Spectrum
  • 29.4 Photon Momentum
  • 29.5 The Particle-Wave Duality
  • 29.6 The Wave Nature of Matter
  • 29.7 Probability: The Heisenberg Uncertainty Principle
  • 29.8 The Particle-Wave Duality Reviewed
  • Introduction to Atomic Physics
  • 30.1 Discovery of the Atom
  • 30.2 Discovery of the Parts of the Atom: Electrons and Nuclei
  • 30.3 Bohr’s Theory of the Hydrogen Atom
  • 30.4 X Rays: Atomic Origins and Applications
  • 30.5 Applications of Atomic Excitations and De-Excitations
  • 30.6 The Wave Nature of Matter Causes Quantization
  • 30.7 Patterns in Spectra Reveal More Quantization
  • 30.8 Quantum Numbers and Rules
  • 30.9 The Pauli Exclusion Principle
  • Introduction to Radioactivity and Nuclear Physics
  • 31.1 Nuclear Radioactivity
  • 31.2 Radiation Detection and Detectors
  • 31.3 Substructure of the Nucleus
  • 31.4 Nuclear Decay and Conservation Laws
  • 31.5 Half-Life and Activity
  • 31.6 Binding Energy
  • 31.7 Tunneling
  • Introduction to Applications of Nuclear Physics
  • 32.1 Diagnostics and Medical Imaging
  • 32.2 Biological Effects of Ionizing Radiation
  • 32.3 Therapeutic Uses of Ionizing Radiation
  • 32.4 Food Irradiation
  • 32.5 Fusion
  • 32.6 Fission
  • 32.7 Nuclear Weapons
  • Introduction to Particle Physics
  • 33.1 The Yukawa Particle and the Heisenberg Uncertainty Principle Revisited
  • 33.2 The Four Basic Forces
  • 33.3 Accelerators Create Matter from Energy
  • 33.4 Particles, Patterns, and Conservation Laws
  • 33.5 Quarks: Is That All There Is?
  • 33.6 GUTs: The Unification of Forces
  • Introduction to Frontiers of Physics
  • 34.1 Cosmology and Particle Physics
  • 34.2 General Relativity and Quantum Gravity
  • 34.3 Superstrings
  • 34.4 Dark Matter and Closure
  • 34.5 Complexity and Chaos
  • 34.6 High-temperature Superconductors
  • 34.7 Some Questions We Know to Ask
  • A | Atomic Masses
  • B | Selected Radioactive Isotopes
  • C | Useful Information
  • D | Glossary of Key Symbols and Notation

Learning Objectives

By the end of this section, you will be able to:

  • Explain the difference between a principle and a law.
  • Explain the difference between a model and a theory.

The physical universe is enormously complex in its detail. Every day, each of us observes a great variety of objects and phenomena. Over the centuries, the curiosity of the human race has led us collectively to explore and catalog a tremendous wealth of information. From the flight of birds to the colors of flowers, from lightning to gravity, from quarks to clusters of galaxies, from the flow of time to the mystery of the creation of the universe, we have asked questions and assembled huge arrays of facts. In the face of all these details, we have discovered that a surprisingly small and unified set of physical laws can explain what we observe. As humans, we make generalizations and seek order. We have found that nature is remarkably cooperative—it exhibits the underlying order and simplicity we so value.

It is the underlying order of nature that makes science in general, and physics in particular, so enjoyable to study. For example, what do a bag of chips and a car battery have in common? Both contain energy that can be converted to other forms. The law of conservation of energy (which says that energy can change form but is never lost) ties together such topics as food calories, batteries, heat, light, and watch springs. Understanding this law makes it easier to learn about the various forms energy takes and how they relate to one another. Apparently unrelated topics are connected through broadly applicable physical laws, permitting an understanding beyond just the memorization of lists of facts.

The unifying aspect of physical laws and the basic simplicity of nature form the underlying themes of this text. In learning to apply these laws, you will, of course, study the most important topics in physics. More importantly, you will gain analytical abilities that will enable you to apply these laws far beyond the scope of what can be included in a single book. These analytical skills will help you to excel academically, and they will also help you to think critically in any professional career you choose to pursue. This module discusses the realm of physics (to define what physics is), some applications of physics (to illustrate its relevance to other disciplines), and more precisely what constitutes a physical law (to illuminate the importance of experimentation to theory).

Science and the Realm of Physics

Science consists of the theories and laws that are the general truths of nature as well as the body of knowledge they encompass. Scientists are continually trying to expand this body of knowledge and to perfect the expression of the laws that describe it. Physics is concerned with describing the interactions of energy, matter, space, and time, and it is especially interested in what fundamental mechanisms underlie every phenomenon. The concern for describing the basic phenomena in nature essentially defines the realm of physics .

Physics aims to describe the function of everything around us, from the movement of tiny charged particles to the motion of people, cars, and spaceships. In fact, almost everything around you can be described quite accurately by the laws of physics. Consider a smart phone ( Figure 1.3 ). Physics describes how electricity interacts with the various circuits inside the device. This knowledge helps engineers select the appropriate materials and circuit layout when building the smart phone. Next, consider a GPS system. Physics describes the relationship between the speed of an object, the distance over which it travels, and the time it takes to travel that distance. GPS relies on precise calculations that account for variations in the Earth's landscapes, the exact distance between orbiting satellites, and even the effect of a complex occurrence of time dilation. Most of these calculations are founded on algorithms developed by Gladys West, a mathematician and computer scientist who programmed the first computers capable of highly accurate remote sensing and positioning. When you use a GPS device, it utilizes these algorithms to recognize where you are and how your position relates to other objects on Earth.

Applications of Physics

You need not be a scientist to use physics. On the contrary, knowledge of physics is useful in everyday situations as well as in nonscientific professions. It can help you understand how microwave ovens work, why metals should not be put into them, and why they might affect pacemakers. (See Figure 1.4 and Figure 1.5 .) Physics allows you to understand the hazards of radiation and rationally evaluate these hazards more easily. Physics also explains the reason why a black car radiator helps remove heat in a car engine, and it explains why a white roof helps keep the inside of a house cool. Similarly, the operation of a car’s ignition system as well as the transmission of electrical signals through our body’s nervous system are much easier to understand when you think about them in terms of basic physics.

Physics is the foundation of many important disciplines and contributes directly to others. Chemistry, for example—since it deals with the interactions of atoms and molecules—is rooted in atomic and molecular physics. Most branches of engineering are applied physics. In architecture, physics is at the heart of structural stability, and is involved in the acoustics, heating, lighting, and cooling of buildings. Parts of geology rely heavily on physics, such as radioactive dating of rocks, earthquake analysis, and heat transfer in the Earth. Some disciplines, such as biophysics and geophysics, are hybrids of physics and other disciplines.

Physics has many applications in the biological sciences. On the microscopic level, it helps describe the properties of cell walls and cell membranes ( Figure 1.6 and Figure 1.7 ). On the macroscopic level, it can explain the heat, work, and power associated with the human body. Physics is involved in medical diagnostics, such as x-rays, magnetic resonance imaging (MRI), and ultrasonic blood flow measurements. Medical therapy sometimes directly involves physics; for example, cancer radiotherapy uses ionizing radiation. Physics can also explain sensory phenomena, such as how musical instruments make sound, how the eye detects color, and how lasers can transmit information.

It is not necessary to formally study all applications of physics. What is most useful is knowledge of the basic laws of physics and a skill in the analytical methods for applying them. The study of physics also can improve your problem-solving skills. Furthermore, physics has retained the most basic aspects of science, so it is used by all of the sciences, and the study of physics makes other sciences easier to understand.

Models, Theories, and Laws; The Role of Experimentation

The laws of nature are concise descriptions of the universe around us; they are human statements of the underlying laws or rules that all natural processes follow. Such laws are intrinsic to the universe; humans did not create them and so cannot change them. We can only discover and understand them. Their discovery is a very human endeavor, with all the elements of mystery, imagination, struggle, triumph, and disappointment inherent in any creative effort. (See Figure 1.8 and Figure 1.9 .) The cornerstone of discovering natural laws is observation; science must describe the universe as it is, not as we may imagine it to be.

We all are curious to some extent. We look around, make generalizations, and try to understand what we see—for example, we look up and wonder whether one type of cloud signals an oncoming storm. As we become serious about exploring nature, we become more organized and formal in collecting and analyzing data. We attempt greater precision, perform controlled experiments (if we can), and write down ideas about how the data may be organized and unified. We then formulate models, theories, and laws based on the data we have collected and analyzed to generalize and communicate the results of these experiments.

A model is a representation of something that is often too difficult (or impossible) to display directly. While a model is justified with experimental proof, it is only accurate under limited situations. An example is the planetary model of the atom in which electrons are pictured as orbiting the nucleus, analogous to the way planets orbit the Sun. (See Figure 1.10 .) We cannot observe electron orbits directly, but the mental image helps explain the observations we can make, such as the emission of light from hot gases (atomic spectra). Physicists use models for a variety of purposes. For example, models can help physicists analyze a scenario and perform a calculation, or they can be used to represent a situation in the form of a computer simulation. A theory is an explanation for patterns in nature that is supported by scientific evidence and verified multiple times by various groups of researchers. Some theories include models to help visualize phenomena, whereas others do not. Newton’s theory of gravity, for example, does not require a model or mental image, because we can observe the objects directly with our own senses. The kinetic theory of gases, on the other hand, is a model in which a gas is viewed as being composed of atoms and molecules. Atoms and molecules are too small to be observed directly with our senses—thus, we picture them mentally to understand what our instruments tell us about the behavior of gases.

A law uses concise language to describe a generalized pattern in nature that is supported by scientific evidence and repeated experiments. Often, a law can be expressed in the form of a single mathematical equation. Laws and theories are similar in that they are both scientific statements that result from a tested hypothesis and are supported by scientific evidence. However, the designation law is reserved for a concise and very general statement that describes phenomena in nature, such as the law that energy is conserved during any process, or Newton’s second law of motion, which relates force, mass, and acceleration by the simple equation F = m a F = m a . A theory, in contrast, is a less concise statement of observed phenomena. For example, the Theory of Evolution and the Theory of Relativity cannot be expressed concisely enough to be considered a law. The biggest difference between a law and a theory is that a theory is much more complex and dynamic. A law describes a single action, whereas a theory explains an entire group of related phenomena. And, whereas a law is a postulate that forms the foundation of the scientific method, a theory is the end result of that process.

Less broadly applicable statements are usually called principles (such as Pascal’s principle, which is applicable only in fluids), but the distinction between laws and principles often is not carefully made.

Models, Theories, and Laws

Models, theories, and laws are used to help scientists analyze the data they have already collected. However, often after a model, theory, or law has been developed, it points scientists toward new discoveries they would not otherwise have made.

The models, theories, and laws we devise sometimes imply the existence of objects or phenomena as yet unobserved. These predictions are remarkable triumphs and tributes to the power of science. It is the underlying order in the universe that enables scientists to make such spectacular predictions. However, if experiment does not verify our predictions, then the theory or law is wrong, no matter how elegant or convenient it is. Laws can never be known with absolute certainty because it is impossible to perform every imaginable experiment in order to confirm a law in every possible scenario. Physicists operate under the assumption that all scientific laws and theories are valid until a counterexample is observed. If a good-quality, verifiable experiment contradicts a well-established law, then the law must be modified or overthrown completely.

The study of science in general and physics in particular is an adventure much like the exploration of uncharted ocean. Discoveries are made; models, theories, and laws are formulated; and the beauty of the physical universe is made more sublime for the insights gained.

The Scientific Method

Ibn al-Haytham (sometimes referred to as Alhazen), a 10th-11th century scientist working in Cairo, significantly advanced the understanding of optics and vision. But his contributions go much further. In demonstrating that previous approaches were incorrect, he emphasized that scientists must be ready to reject existing knowledge and become "the enemy" of everything they read; he expressed that scientists must trust only objective evidence. Al-Haytham emphasized repeated experimentation and validation, and acknowledged that senses and predisposition could lead to poor conclusions. His work was a precursor to the scientific method that we use today.

As scientists inquire and gather information about the world, they follow a process called the scientific method . This process typically begins with an observation and question that the scientist will research. Next, the scientist typically performs some research about the topic and then devises a hypothesis. Then, the scientist will test the hypothesis by performing an experiment. Finally, the scientist analyzes the results of the experiment and draws a conclusion. Note that the scientific method can be applied to many situations that are not limited to science, and this method can be modified to suit the situation.

Consider an example. Let us say that you try to turn on your car, but it will not start. You undoubtedly wonder: Why will the car not start? You can follow a scientific method to answer this question. First off, you may perform some research to determine a variety of reasons why the car will not start. Next, you will state a hypothesis. For example, you may believe that the car is not starting because it has no engine oil. To test this, you open the hood of the car and examine the oil level. You observe that the oil is at an acceptable level, and you thus conclude that the oil level is not contributing to your car issue. To troubleshoot the issue further, you may devise a new hypothesis to test and then repeat the process again.

The Evolution of Natural Philosophy into Modern Physics

Physics was not always a separate and distinct discipline. It remains connected to other sciences to this day. The word physics comes from Greek, meaning nature. The study of nature came to be called “natural philosophy.” From ancient times through the Renaissance, natural philosophy encompassed many fields, including astronomy, biology, chemistry, physics, mathematics, and medicine. Over the last few centuries, the growth of knowledge has resulted in ever-increasing specialization and branching of natural philosophy into separate fields, with physics retaining the most basic facets. (See Figure 1.11 , Figure 1.12 , and Figure 1.13 .) Physics as it developed from the Renaissance to the end of the 19th century is called classical physics . It was transformed into modern physics by revolutionary discoveries made starting at the beginning of the 20th century.

Classical physics is not an exact description of the universe, but it is an excellent approximation under the following conditions: Matter must be moving at speeds less than about 1% of the speed of light, the objects dealt with must be large enough to be seen with a microscope, and only weak gravitational fields, such as the field generated by the Earth, can be involved. Because humans live under such circumstances, classical physics seems intuitively reasonable, while many aspects of modern physics seem bizarre. This is why models are so useful in modern physics—they let us conceptualize phenomena we do not ordinarily experience. We can relate to models in human terms and visualize what happens when objects move at high speeds or imagine what objects too small to observe with our senses might be like. For example, we can understand an atom’s properties because we can picture it in our minds, although we have never seen an atom with our eyes. New tools, of course, allow us to better picture phenomena we cannot see. In fact, new instrumentation has allowed us in recent years to actually “picture” the atom.

Limits on the Laws of Classical Physics

For the laws of classical physics to apply, the following criteria must be met: Matter must be moving at speeds less than about 1% of the speed of light, the objects dealt with must be large enough to be seen with a microscope, and only weak gravitational fields (such as the field generated by the Earth) can be involved.

Some of the most spectacular advances in science have been made in modern physics. Many of the laws of classical physics have been modified or rejected, and revolutionary changes in technology, society, and our view of the universe have resulted. Like science fiction, modern physics is filled with fascinating objects beyond our normal experiences, but it has the advantage over science fiction of being very real. Why, then, is the majority of this text devoted to topics of classical physics? There are two main reasons: Classical physics gives an extremely accurate description of the universe under a wide range of everyday circumstances, and knowledge of classical physics is necessary to understand modern physics.

Modern physics itself consists of the two revolutionary theories, relativity and quantum mechanics. These theories deal with the very fast and the very small, respectively. Relativity must be used whenever an object is traveling at greater than about 1% of the speed of light or experiences a strong gravitational field such as that near the Sun. Quantum mechanics must be used for objects smaller than can be seen with a microscope. The combination of these two theories is relativistic quantum mechanics, and it describes the behavior of small objects traveling at high speeds or experiencing a strong gravitational field. Relativistic quantum mechanics is the best universally applicable theory we have. Because of its mathematical complexity, it is used only when necessary, and the other theories are used whenever they will produce sufficiently accurate results. We will find, however, that we can do a great deal of modern physics with the algebra and trigonometry used in this text.

Check Your Understanding

A friend tells you they have learned about a new law of nature. What can you know about the information even before your friend describes the law? How would the information be different if your friend told you they had learned about a scientific theory rather than a law?

Without knowing the details of the law, you can still infer that the information your friend has learned conforms to the requirements of all laws of nature: it will be a concise description of the universe around us; a statement of the underlying rules that all natural processes follow. If the information had been a theory, you would be able to infer that the information will be a large-scale, broadly applicable generalization.

PhET Explorations

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Learn about graphing polynomials. The shape of the curve changes as the constants are adjusted. View the curves for the individual terms (e.g. y = bx y = bx ) to see how they add to generate the polynomial curve.

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Notes to Experiment in Physics

1. As the late Richard Feynman, one of the leading theoretical physicists of the twentieth century, wrote:

The principle of science, the definition, almost, is the following: The test of all knowledge is experiment . Experiment is the sole judge of scientific ‘truth’. (Feynman, Leighton and Sands 1963, p. 1-1)

In these postmodern times this might seem to be an old-fashioned view, but it is, I believe, correct. Not everyone would agree. As Andy Pickering has remarked,

…there is no obligation upon anyone framing a view of the world to take account of what twentieth-century science has to say. (Pickering 1984a, p. 413)

2. By valid, I mean that the experimental result has been argued for in the correct way, by use of epistemological strategies such as those discussed below.

3. See Franklin (1986, Ch. 6; and, 1990, Ch. 6) and Franklin and Howson (1984) for details of these strategies, along with a discussion of how they fit into a Bayesian philosophy of science

4. As Holmes remarked to Watson, “How often have I said to you that when you have eliminated the impossible, whatever remains, however improbable , must be the truth.” (Conan Doyle 1967, p. 638)

5. It might be useful here to distinguish between the theory of the apparatus and the theory of the phenomenon. Ackermann is talking primarily about the later. It may not always be possible to separate these two theories. The analysis of the data obtained from an instrument may very well involve the theory of the phenomenon, but that doesn’t necessarily cast doubt on the validity of the experimental result.

6. For another episode in which the elimination of background was crucial see the discussion of the measurement of the \(\ce{K+_{e 2}}\) branching ratio in (Franklin 1990, pp. 115–31).

7. Collins offers two arguments concerning the difficulty, if not the virtual impossibility of replication. The first is philosophical. What does it mean to replicate an experiment? In what way is the replication similar to the original experiment? A rough and ready answer is that the replication measures the same physical quantity. Whether or not it, in fact, does so can, I believe, be argued for on reasonable grounds, as discussed earlier.

Collins’ second argument is pragmatic. This is the fact that in practice it is often difficult to get an experimental apparatus, even one known to be similar to another, to work properly. Collins illustrates this with his account of Harrison’s attempts to construct two versions of a TEA laser (Transverse Excited Atmospheric) (Collins 1985, pp. 51–78). Despite the fact that Harrison had previous experience with such lasers, and had excellent contacts with experts in the field, he had great difficulty in building the lasers. Hence the difficulty of replication.

Ultimately Harrison found errors in his apparatus and once these were corrected the lasers operated properly. As Collins admits, “…in the case of the TEA laser the circle was readily broken. The ability of the laser to vaporize concrete, or whatever, comprised a universally agreed criterion of experimental quality. There was never any doubt that the laser ought to be able to work and never any doubt about when one was working and when it was not.” (Collins 1985, p. 84)

Although Collins seems to regard Harrison’s problems with replication as casting light on the episode of gravity waves, as support for the experimenters’ regress, and as casting doubt on experimental evidence in general, it really doesn’t work. As Collins admits (see quote in last paragraph), the replication was clearly demonstrable. One may wonder what role Collins thinks this episode plays in his argument.

8. In more detailed discussions of this episode, Franklin (1994, 1997a), I argued that the gravity wave experiment is not at all typical of physics experiments. In most experiments, as illustrated in those essays, the adequacy of the surrogate signal used in the calibration of the experimental apparatus is clear and unproblematical. In cases where it is questionable considerable effort is devoted to establishing the adequacy of that surrogate signal. Although Collins has chosen an atypical example I believe that the questions he raises about calibration in general and about this particular episode of gravity wave experiments should be answered.

9. Weber had suggested that the actual gravity wave pulses were longer that expected, and that the nonlinear analysis algorithm was more efficient at detecting such pulses.

10. The \(\ce{K1^0}\) and \(\ce{K2^0}\) mesons were elementary particles with the same charge, mass, and intrinsic spin. They did, however, differ with respect to the \(CP\) operator. The \(\ce{K1^0}\) and \(\ce{K2^0}\) mesons were eigenstates of the \(CP\) operator with eigenvalues \(CP = +1\) and \(-1\), respectively.

11. Bose’s paper had originally been rejected by the Philosophical Magazine . He then sent it, in English, to Einstein with a request that if Einstein thought the paper merited publication that he would arrange for publication in the Zeitschrift fur Physik . Einstein personally translated the paper and submitted it to the Zeitschrift fur Physik , adding a translator’s note, “In my opinion, Bose’s derivation of the Planck formula constitutes an important advance. The method used here also yields the quantum theory of the ideal gas, as I shall discuss elsewhere in more detail” (Pais 1982, p. 423). This discussion appeared in Einstein’s own papers of 1924 and 1925. For details see Pais (1982, Ch. 23).

12. This section is based on the accounts given by Weinert (1995) and by Mehra and Rechenberg (1982). Translations from the German were provided by these authors and are indicated by initials in the text.

13. See also pp. 224–226 in (Franklin 2013).

Notes to Appendix 2

1. I surveyed eighty such theoretical papers. Sixty accepted the Princeton result as evidence for either CP violation or apparent CP violation. Even those that offered alternative explanations of the result were not necessarily indications that the authors did not accept CP violation. One should distinguish between interesting speculations and serious suggestions. The latter are characterized by a commitment to their truth. I note that T.D. Lee was author, or co-author, of three of these theoretical papers. Two offered alternative explanations of the Princeton result and one proposed a model that avoided CP violation. Lee was not seriously committed to the truth of any of them. Bell and Perring, authors of one of the alternatives, remarked, “Before a more mundane explanation is found it is amusing to speculate that it might be a local effect due to the dysymmetry of the environment, namely the local preponderance of matter over antimatter” (Bell and Perring 1964, p. 348, emphasis added).

2. In the modus tollens if \(h\) entails \(e\) then “not \(e\)” entails not \(h\). Duhem and Quine pointed out that it is really \(h\) and \(b\), where \(b\) is background knowledge and auxiliary hypotheses, that entails \(e\). Thus “not \(e\)” entails “\(h\)” or “\(b\)” and one doesn’t know where to place the blame.

Notes to Appendix 3

1. Bose’s paper had originally been rejected by the Philosophical Magazine . He then sent it, in English, to Einstein with a request that if Einstein thought the paper merited publication that he would arrange for publication in the Zeitschrift fur Physik . Einstein personally translated the paper and submitted it to the Zeitschrift fur Physik , adding a translator’s note, “In my opinion, Bose’s derivation of the Planck formula constitutes an important advance. The method used here also yields the quantum theory of the ideal gas, as I shall discuss elsewhere in more detail” (Pais 1982, p. 423). This discussion appeared in Einstein’s own papers of 1924 and 1925. For details see Pais (1982, Ch. 23).

2. One difficulty with using rubidium is that at very low temperatures rubidium should be a solid. (In fact, rubidium is a solid at room temperature). Wieman, Cornell and their collaborators avoided this difficulty by creating a system that does not reach a true equilibrium. The vapor sample created equilibrates to a thermal distribution as a spin polarized gas, but takes a very long time to reach its true equilibrium state as a solid. At the low temperatures and density of the experiment the rubidium remains as a metastable super-saturated vapor for a long time.

Notes to Appendix 4

1. The original Eötvös experiment was designed to measure the ratio of the gravitational mass to the inertial mass of different substances. Eötvös found the ratio to be one, to within approximately one part in a million. Fischbach and his collaborators reanalyzed Eötvös’ data and found a composition dependent effect, which they interpreted as evidence for a Fifth Force.

2. It is a fact of experimental life that experiments rarely work when they are initially turned on and that experimental results can be wrong, even if there is no apparent error. It is not necessary to know the exact source of an error in order to discount or to distrust a particular experimental result. Its disagreement with numerous other results can, I believe, be sufficient.

Notes to Appendix 6

1. Rupp’s withdrawal included a note from a psychiatrist stating that Rupp had suffered from a mental illness and could not distinguish between fantasy and reality.

2. The problem with the hydrogen spectrum was not solved until the later discovery of the anomalous magnetic moment of the electron in the 1950s.

Notes to Appendix 7

1. Morrison (1990) has argued that manipulability is not sufficient to establish belief in an entity. She discusses particle physics experiments in which particle beams were viewed not only as particles, but also as beams of quarks, the constituents of the particles, even though the physicists involved had no belief in the existence of quarks. Although I believe that Morrison’s argument is correct in this particular case, I do think that manipulability can, and often does, give us good reason to believe in an entity. See, for example, the discussion of the microscope in Hacking (1983).

2. Millikan, for example, used the properties of electrons emitted in the photoelectric effect to measure h , Planck’s constant. Stern and Gerlach, as discussed below, used the properties of the electron to investigate spatial quantization, and also discovered evidence for electron spin.

3. In Cartwright’s discussion of the electron track in the cloud chamber, for example, she can identify the track as an electron track rather than as a proton track only because she has made an implicit commitment to the law of ionization for charged particles, and it’s dependence on the mass and velocity of the particles.

4. Thomson also demonstrated the magnetic deflection of cathode rays in a separate experiment.

5. Thomson actually investigated the conductivity of the gas in the tube under varying pressure conditions. See Thomson (1897, pp. 298–300).

6. I shall return to this when I discuss Thomson’s measurement of e/m for the electron.

7. Thomson’s argument is the “duck argument.” If it looks like a duck, quacks like a duck, and waddles like a duck, then we have good reason to believe that it is a duck. One need only reconstitute the argument using “it” as cathode rays and negatively charged particles as ducks.

8. Thomson actually used two different methods to determine the charge to mass ratio. The other method used the total charge carried by a beam of cathode rays in a fixed period of time, the total energy carried by the beam in that same time, and the radius of curvature of the particles in a known magnetic field. Thomson regarded the method discussed in the text as more reliable and this is the method shown in most modern physics textbooks.

9. Not everything Thomson concluded is in agreement with modern views. Although he believed that the electron was a constituent of atoms, he thought that it was the primordial atom from which all atoms were constructed, similar to Prout’s view that all atoms were constructed from hydrogen atoms. He also suggested that the charge on the electron might be larger than that of the hydrogen ion.

Notes to Appendix 8

1. The conservation of momentum also requires that the electron and proton have equal and opposite momenta, for a neutron decay at rest. They will be emitted in opposite directions.

2. Pauli’s suggestion was first made in a December 4, 1930 letter to the radioactive group at a regional meeting in Tuebingen.

Dear Radioactive Ladies and Gentlemen: I beg you to receive graciously the bearer of this letter who will report to you in detail how I have hit on a desperate was to escape from the problems of the “wrong” statistics of the N and Li 6 nuclei and of the continuous beta spectrum in order to save the “even-odd” rule of statistics and the law of conservation of energy. Namely the possibility that electrically neutral particles, which I would like to call neutrons [the particle we call the neutron, which is about the same mass as the proton, was discovered in 1932 by Chadwick. Pauli’s “neutron” is our “neutrino.”] might exist inside nuclei; these would have spin 1/2, would obey the exclusion principle, and would in addition duffer from photons through the fact that they would not travel at the speed of light. The mass of the neutron ought to be about the same order of magnitude as the electron mass, and in any case could not be greater than 0.01 proton masses. The continuous beta spectrum would then become understandable by assuming that in beta decay a neutron is always emitted along with the electron, in such a way that the sum of the energies of the neutron and electron is a constant. Now, the question is, what forces act on the neutron? The most likely model for the neutron seems to me, on wave mechanical grounds, to be the assumption that the motionless neutron is a magnetic dipole with a certain magnetic moment \(\mu\) (the bearer of this letter can supply details). The experiments demand that the ionizing power of such a neutron cannot exceed that of a gamma ray, and therefore \(\mu\) probably cannot be greater than \(e \cdot (10^{-13}\text{cm})\). [\(e\) is the charge of the electron]. At the moment I do not dare to publish anything about this idea, so I first turn trustingly to you, dear radioactive friends, with the question: how could such a neutron be experimentally identified if it possessed about the same penetrating power as a gamma ray or perhaps 10 times greater penetrating power? I admit that my way out may look rather improbable at first since if the neutron existed it would have been seen long ago. But nothing ventured, nothing gained. The gravity of the situation with the continuous beta spectrum was illuminated by a remark by my distinguished predecessor in office, Mr. DeBye, who recently said to me in Brussels, “Oh, that’s a problem like the new taxes; one had best not think about it at all.” So one ought to discuss seriously any way that may lead to salvation. Well, dear radioactive friends, weigh it and pass sentence! Unfortunately, I cannot appear personally in Tubingen, for I cannot get away from Zurich on account of a ball which is held here on the night of December 6–7. With best regards to you and to Mr. Baek, Your most obedient servant,     W. Pauli (Quoted in Ford 1968, p. 849.)

This was a serious suggestion and although Pauli did not get all the properties of the neutrino right his suggestion was the basis of further work.

3. With a three-body decay the electron and the proton also didn’t have to come off back to back. This observation was not made until the late 1930s. Assigning the neutrino a spin, intrinsic angular momentum, of \(h/4\) also preserved the law of conservation of angular momentum.

4. The actual history is more complex. For a time, an alternative theory of decay, proposed by Konopinski and Uhlenbeck (1935) was better supported by the experimental evidence than was Fermi’s theory. It was subsequently shown that both the experimental results and the theoretical calculations were wrong and that Fermi’s theory was, in fact, supported by the evidence. For details see (Franklin 1990).

5. Allowed transitions are those for which both the electron and neutrino wavefunctions could be considered constant over nuclear dimensions. Forbidden transitions are those that included higher order terms in the perturbation series expansion of the matrix element.

6. I have been unable to find a published reference to this measurement. It is cited as a private communication in the literature.

7. In a post-deadline paper presented at the January 1958 meeting of the American Physical Society, Rustad and Ruby suggested that their earlier result might be wrong. There are no abstracts of post-deadline papers, but the talk was cited in the literature. Ruby remembers the tone of the paper as mea culpa (private communication).

Copyright © 2023 by Allan Franklin < allan . franklin @ colorado . edu > Slobodan Perovic < sperovic @ f . bg . ac . rs >

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New Fundamental Physics Uncovered – Experiments Prove the Existence of a New Type of Magnetism

By Miriam Arrell, Paul Scherrer Institute February 14, 2024

New Magnetism Concept

Altermagnetism introduces a third magnetic phase, combining the non-magnetization of antiferromagnets with the strong spin-dependent phenomena of ferromagnets. Discovered through international collaboration, this new phase offers significant potential for spintronics, bridging previous gaps in magnetic material applications. Credit: SciTechDaily.com

Experiments at the Swiss Light Source SLS prove the existence of a new type of magnetism, with broad implications for technology and research.

There is now a new addition to the magnetic family: thanks to experiments at the Swiss Light Source SLS, researchers have proved the existence of altermagnetism. The experimental discovery of this new branch of magnetism is reported in Nature and signifies new fundamental physics, with major implications for spintronics.

Magnetism is a lot more than just things that stick to the fridge. This understanding came with the discovery of antiferromagnets nearly a century ago. Since then, the family of magnetic materials has been divided into two fundamental phases: the ferromagnetic branch known for several millennia and the antiferromagnetic branch. The experimental proof of a third branch of magnetism, termed altermagnetism, was made at the Swiss Light Source (SLS), by an international collaboration led by the Czech Academy of Sciences together with Paul Scherrer Institute (PSI).

The fundamental magnetic phases are defined by the specific spontaneous arrangements of magnetic moments – or electron spins – and of atoms that carry the moments in crystals. Ferromagnets are the type of magnets that stick to the fridge: here spins point in the same direction, giving macroscopic magnetism. In antiferromagnetic materials, spins point in alternating directions, with the result that the materials possess no macroscopic net magnetization – and thus don’t stick to the fridge. Although other types of magnetism, such as diamagnetism and paramagnetism have been categorized, these describe specific responses to externally applied magnetic fields rather than spontaneous magnetic orderings in materials.

Discovery and Properties of Altermagnets

Altermagnets have a special combination of the arrangement of spins and crystal symmetries. The spins alternate, as in antiferromagnets, resulting in no net magnetization. Yet, rather than simply canceling out, the symmetries give an electronic band structure with strong spin polarization that flips in direction as you pass through the material’s energy bands – hence the name altermagnets. This results in highly useful properties more resemblant of ferromagnets, as well as some completely new properties.

Juraj Krempasky at Swiss Light Source SLS

In Nature, researchers report the discovery of a new type of fundamental magnetism, termed ‘altermagnetism’. Here, Juraj Krempasky, scientist at PSI and first author of the publication stands at the Swiss Light Source SLS where the experimental proof of altermagnetism was made. Credit: Paul Scherrer Institut / Mahir Dzambegovic

Implications for Spintronics

This third magnetic sibling offers distinct advantages for the developing field of next-generation magnetic memory technology, known as spintronics. Whereas electronics makes use only of the charge of the electrons, spintronics also exploits the spin-state of electrons to carry information.

Although spintronics has for some years promised to revolutionize IT, it’s still in its infancy. Typically, ferromagnets have been used for such devices, as they offer certain highly desirable strong spin-dependent physical phenomena. Yet the macroscopic net magnetization that is useful in so many other applications poses practical limitations on the scalability of these devices as it causes crosstalk between bits – the information carrying elements in data storage.

More recently, antiferromagnets have been investigated for spintronics, as they benefit from having no net magnetization and thus offer ultra-scalability and energy efficiency. However, the strong spin-dependent effects that are so useful in ferromagnets are lacking, again hindering their practical applicability.

Here enter altermagnets with the best of both: zero net magnetisation together with the coveted strong spin-dependent phenomena typically found in ferromagnets – merits that were regarded as principally incompatible.

“That’s the magic about altermagnets,” says Tomáš Jungwirth from the Institute of Physics of the Czech Academy of Sciences, principal investigator of the study. “Something that people believed was impossible until recent theoretical predictions is in fact possible.”

Theoretical Predictions and Experimental Validation

Murmurings that a new type of magnetism was lurking began not long ago: In 2019, Jungwirth together with theoretical colleagues at the Czech Academy of Sciences and University of Mainz identified a class of magnetic materials with a spin structure that did not fit within the classic descriptions of ferromagnetism or antiferromagnetism.

In 2022, the theorists published their predictions of the existence of altermagnetism. They uncovered more than two hundred altermagnetic candidates in materials ranging from insulators and semiconductors , to metals and superconductors. Many of these materials have been well known and extensively explored in the past, without noticing their altermagnetic nature. Due to the huge research and application opportunities that altermagnetism poses, these predictions caused great excitement within the community. The search was on.

Obtaining direct experimental proof of altermagnetism’s existence required demonstrating the unique spin symmetry characteristics predicted in altermagnets. The proof came using spin- and angle resolved photoemission spectroscopy at the SIS (COPHEE endstation) and ADRESS beamlines of the SLS. This technique enabled the team to visualize a tell-tale feature in the electronic structure of a suspected altermagnet: the splitting of electronic bands corresponding to different spin states, known as the lifting of Kramers spin degeneracy.

The discovery was made in crystals of manganese telluride, a well-known simple two-element material. Traditionally, the material has been regarded as a classic antiferromagnet because the magnetic moments on neighboring manganese atoms point in opposite directions, generating a vanishing net magnetization.

“Now that we have brought it to light, many people around the world will be able to work on it.” — Tomáš Jungwirth

However, antiferromagnets should not exhibit lifted Kramers spin degeneracy by the magnetic order, whereas ferromagnets or altermagnets should. When the scientists saw the lifting of Kramers spin degeneracy, accompanied by the vanishing net magnetization, they knew they were looking at an altermagnet.

“Thanks to the high precision and sensitivity of our measurements, we could detect the characteristic alternating splitting of the energy levels corresponding to opposite spin states and thus demonstrate that manganese telluride is neither a conventional antiferromagnet nor a conventional ferromagnet but belongs to the new altermagnetic branch of magnetic materials,” says Juraj Krempasky, beamline scientist in the Beamline Optics Group at PSI and first author of the study.

The beamlines that enabled this discovery are now disassembled, awaiting the SLS 2.0 upgrade. After twenty years of successful science, the COPHEE endstation will be completely integrated into the new ‘QUEST’ beamline. “It was with the last photons of light at COPHEE that we made these experiments. That they gave such an important scientific breakthrough is very emotional for us,” adds Krempasky.

Conclusion and Future Directions

The researchers believe that this new fundamental discovery in magnetism will enrich our understanding of condensed-matter physics, with impact across diverse areas of research and technology. As well as its advantages to the developing field of spintronics, it also offers a promising platform for exploring unconventional superconductivity, through new insights into superconducting states that can arise in different magnetic materials.

“Altermagnetism is actually not something hugely complicated. It is something entirely fundamental that was in front of our eyes for decades without noticing it,” says Jungwirth. “And it is not something that exists only in a few obscure materials. It exists in many crystals that people simply had in their drawers. In that sense, now that we have brought it to light, many people around the world will be able to work on it, giving the potential for a broad impact.”

Reference: “Altermagnetic lifting of Kramers spin degeneracy” by J. Krempaský, L. Šmejkal, S. W. D’Souza, M. Hajlaoui, G. Springholz, K. Uhlířová, F. Alarab, P. C. Constantinou, V. Strocov, D. Usanov, W. R. Pudelko, R. González-Hernández, A. Birk Hellenes, Z. Jansa, H. Reichlová, Z. Šobáň, R. D. Gonzalez Betancourt, P. Wadley, J. Sinova, D. Kriegner, J. Minár, J. H. Dil and T. Jungwirth, 14 February 2024, Nature . DOI: 10.1038/s41586-023-06907-7

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CERN Accelerating science

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Experiments

A range of experiments at CERN investigate physics from cosmic rays to supersymmetry

CMS experiment

Diverse experiments at CERN

CERN is home to a wide range of experiments. Scientists from institutes all over the world form experimental collaborations to carry out a diverse research programme , ensuring that CERN covers a wealth of topics in physics, from the Standard Model to supersymmetry and from exotic isotopes to cosmic rays .

Several collaborations run experiments using the Large Hadron Collider (LHC), the most powerful accelerator in the world. In addition, fixed-target experiments, antimatter experiments and experimental facilities make use of the LHC injector chain.

LHC experiments

Nine experiments at the Large Hadron Collider  (LHC) use detectors to analyse the myriad of particles produced by collisions in the accelerator . These experiments are run by collaborations of scientists from institutes all over the world. Each experiment is distinct and characterised by its detectors.

Large Hadron Collider,LHC,Magnets,Dipole,Work,Tunnel

The biggest of these experiments, ATLAS and CMS , use general-purpose detectors to investigate the largest range of physics possible. Having two independently designed detectors is vital for cross-confirmation of any new discoveries made.  ALICE and LHCb  have detectors specialised for focussing on specific phenomena. These four detectors sit underground in huge caverns on the LHC ring.

The smallest experiments on the LHC are  TOTEM  and  LHCf , which focus on "forward particles" – protons or heavy ions that brush past each other rather than meeting head on when the beams collide. TOTEM uses detectors positioned on either side of the CMS interaction point, while LHCf is made up of two detectors which sit along the LHC beamline, at 140 metres either side of the ATLAS collision point.  MoEDAL-MAPP uses detectors deployed near LHCb to search for a hypothetical particle called the magnetic monopole. FASER and SND@LHC , the two newest LHC experiments, are situated close to the ATLAS collision point in order to search for light new particles and to study neutrinos.

MoEDAL-MAPP

Fixed-target experiments.

In “fixed-target” experiments, a beam of accelerated particles is directed at a solid, liquid or gas target, which itself can be part of the detection system. 

COMPASS , which looks at the structure of hadrons – particles made of quarks – uses beams from the Super Proton Synchrotron (SPS).

The SPS also feeds the North Area (NA), which houses a number of experiments. NA61/SHINE studies a phase transition between hadrons and quark-gluon plasma, and conducts measurements for experiments involving cosmic rays and long-baseline neutrino oscillations. NA62 uses protons from the SPS to study rare decays of kaons. NA63 directs beams of electrons and positrons onto a variety of targets to study radiation processes in strong electromagnetic fields. NA64 is looking for new particles that would mediate an unknown interaction between visible matter and dark matter. NA65 studies the production of tau neutrinos. UA9 is investigating how crystals could help to steer particle beams in high-energy colliders.

The CLOUD experiment uses beams from the  Proton Synchrotron (PS) to investigate a possible link between cosmic rays and cloud formation. DIRAC , which is now analysing data, is investigating the strong force between quarks.

Antimatter experiments

Currently the Antiproton Decelerator and ELENA serve several experiments that are studying antimatter and its properties:  AEGIS, ALPHA ,  ASACUSA ,  BASE and  GBAR . PUMA is designed to carry antiprotons to ISOLDE . Earlier experiments ( ATHENA , ATRAP  and ACE ) are now completed.

Experimental facilities

Experimental facilities at CERN include ISOLDE , MEDICIS , the neutron time-of-flight facility (n_TOF) and the CERN Neutrino Platform .

CERN Neutrino Platform

Non-accelerator experiments.

Not all experiments rely on CERN’s accelerator complex. AMS , for example, is a CERN-recognised experiment located on the International Space Station, which has its control centre at CERN. The CAST and OSQAR experiments are both looking for hypothetical dark matter particles called axions.

Past experiments

CERN’s experimental programme has consisted of hundreds of experiments spanning decades.

Among these were pioneering experiments for electroweak physics, a branch of physics that unifies the electromagnetic and weak fundamental forces . In 1958, an experiment at the Synchrocyclotron discovered a rare pion decay that spread CERN’s name around the world. Then in 1973, the Gargamelle bubble chamber presented first direct evidence of the weak neutral current. Ten years later, CERN physicists working on the UA1 and UA2 detectors announced the discovery of the W boson in January and Z boson in June – the two carriers of the electroweak force. Two key scientists behind the discoveries – Carlo Rubbia and Simon van der Meer – received the Nobel prize in physics in 1984.

From 1989, the Large Electron-Positron collider (LEP) enabled the ALEPH , DELPHI , L3 and OPAL experiments to put the Standard Model of particle physics on a strong experimental basis. In 2000, LEP made way for the construction of the Large Hadron Collider (LHC) in the same tunnel.

CERN’s huge contributions to electroweak physics are just some of the highlights of the experiments over the years.

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60 Phenomenal Physics Science Experiments For Middle School

December 11, 2023 //  by  Carly Gerson

Physics is a subject that can be difficult for students to understand, so hands-on experiences like experiments are excellent to give your students a better understanding of tricky concepts and theories! Not only do experiments and activities help your kiddos’ understanding but they also create an interactive way to engage them in the learning. Read on to discover 60 phenomenal physics science experiments to try out with your middle school students!

1. Newton’s Cradle

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Newton’s Cradle is a classic physics experiment that uses basic materials to demonstrate kinetic energy and potential energy . Your students will love creating their very own version using some string and straws! This is a great way to demonstrate the basic concept of energy transfer in an engaging way.

Learn More: 123 Homeschool 4 Me

2. Simple Bernoulli Experiment

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The Bernoulli experiment is an excellent way to teach your kids about air pressure. Show your learners how to use construction paper, tape, a bendy straw, a ping pong ball, scissors, and a pencil to create a fun experiment that they can have a go at! This is a simple way to demonstrate to them how large vehicles like planes can stay high in the air. This abstract concept will be brought to life quickly!

3. Car Science Experiment for Air Resistance and Mass

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A physics concept that is sure to be fun to teach your kiddies is the impact of mass on motion! They’ll feel like modern physicists as they place cars with different masses on their race track and time them on their journey! While this may seem like a pretty simple experiment, you can challenge your kids to complete lots of different trials to find out how a range of different factors affects the speed of their cars.

Learn More: Frugal Fun 4 Boys

4. Archimedes’ Screw Simple Machine

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Can water flow up? Your kids will be able to answer this question after completing this fun experiment! The Archimedes’ Screw is a commonly known invention that moves water upward and transfers it from one place to another. Help your learners construct their own using a piece of plastic pipe and some clear plastic tubing, then let them experiment and see if they can make it work!

5. Layering Liquids Density Experiment

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Children will love participating in this tasty and colorful activity. Have your students use different colored juices or beverages to test out the density of each one by creating a density tower! Everyone will watch in amazement as the different colored liquids separate and float to different places in the test tube! 

Learn More: Inspiration Laboratories

6. Launching Easter Eggs Experiment

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This activity would make for an incredibly fun science fair project or a great science activity during the Easter season. Using a mini catapult and plastic eggs, your kiddies will have great fun testing how mass impacts the distance traveled by the egg. This experiment will definitely make you smile!

7. Balloon in a Bottle Properties of Air Experiment

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Challenge your learners to put a balloon inside a plastic bottle and blow it up; sounds easy enough, right? They’ll find this one to be a little trickier than they initially thought! As they work to try to blow up their balloons discuss the properties of air which makes this seemingly simple task almost impossible!

Learn More: Steve Spangler Science

8. How to Make a Pendulum Wave

This physics science project is both fun to make and incredible to look at! Using washers and a few other simple materials like string, your students will be captivated by their experiment for hours on end. Besides being completely mesmerized, they’ll also learn about waves and motion.

Learn More: YouTube

9. Creating Catapults

physics is experiments

A homemade catapult is a great way to use cheap materials in a STEM project. Have your kiddos use simple household and craft materials to determine which combination makes for the best catapult. You can launch anything from scrunched-up paper to marshmallows! Encourage your middle schoolers to consider how they can scientifically measure which catapult is best!

Learn More: Science Gal

10. Inertia Tower Activity

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Raise the stakes with this amazingly fun inertia activity. This creative activity uses sheets of paper or index cards to separate a tower of cups or blocks, which your students then need to pull out quickly without disturbing the tower. Can they remove all the pieces of paper?

Learn More: Perkin’s E-Learning

11. Rice Friction Experiment

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Friction can be a challenging concept to teach middle school students. Thankfully this experiment makes it a little bit easier! Give your kids a better understanding of this tricky concept by using a plastic bottle, funnel, chopstick, and rice. They’ll learn how to increase and decrease friction and will be amazed when this amazing force lets them lift a bottle up with just a single chopstick!

Learn More: Carrots Are Orange

12. Balancing Robot

physics is experiments

Combine arts and crafts and physics with this adorable activity! Use the printable template and have your kids customize their robots, decorating them however they like before cutting them out. Next, you’ll use some putty to stick a penny to the end of each of the robot’s arms. All that’s left is to let them find out where they can get their robots balancing! 

Learn More: Buggy and Buddy

13. Make Your Own Ice Cream in a Bag

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You had us at ice cream! Your kiddies will be so excited to have a go at making their own ice cream using just a few Ziplock bags. Have them start by measuring cream, sugar, and vanilla flavoring into one bag, making sure it’s sealed up. Then, get them to place this bag inside another bag that also has ice and salt inside and shake! Once they’re done learning, make sure you set aside time for some taste testing!

Learn More: Delish

14. Skittles Density Rainbow

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Build the rainbow with this fun density experiment. Start by having your kiddies dissolve Skittles in water, using a different quantity of each color of Skittles in each liquid. They’ll then gently use a pipette to layer their liquids while you discuss how the solids have impacted the density of each liquid!

Learn More: Gift Of Curiosity

15. Dancing Raisins Science Experiment

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Did you know that you can make raisins dance? Ok, well maybe they’re not actually dancing, but they’re definitely doing something! Your learners will love this fun science experiment where they’ll watch as they watch the carbonation and bubbles of the soda water lift the raisins and “make them dance”.

16. Learning With Dry Ice

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Dry ice is so exciting for your little learners! It has almost magical properties that give it a mysterious element that kids are completely captivated by. Using dry ice is a great way to teach students about how clouds are formed and how they eventually evaporate by capturing a dry ice cloud in a bag! You’ll be inspiring future meteorologists with this visually appealing experiment!

Learn More: Penguin Dry Ice

17. Learning About Arches

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Arches are surprisingly impressive feats of architecture. Their unique shape actually makes them surprisingly strong! Teach your kiddos about how heavy-weight objects such as cars on a bridge are supported as they test out different types of arches to see which one holds the most weight!

Learn More: Imagine Childhood

18. Heat Changing Colored Slime

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This unique experiment requires very specific materials, but we promise it’s worth it! Blow your kids’ minds as they learn about thermodynamics and how heat can change the color of certain materials as they make some heat-sensitive color-changing slime! 

Learn More: Left Brain Craft Brain

19. Homemade Marble Run

physics is experiments

Let your kiddies get creative with any materials they can get their hands on with this next activity! Challenge them to create a track for marbles, testing out different course layouts to see how these impact the time it takes the marble to complete it. Encourage them to record their results and share their findings!

Learn More: Buggy And Buddy

20. Ice Hockey Puck Friction Experiment

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The ice hockey fans in your class will love this next one! In this activity, your kids will use different flat circular items like bottle caps and coins to determine which materials make the best ice hockey puck! This is a great experiment to take outside on an icy winter day to let them learn about and see friction in action!

Learn More: Science Sparks

21. Transfer of Momentum Basketball Activity

physics is experiments

Here’s a quick physics experiment your kiddos can do during recess or on a sunny day! Grab some basketballs and racquetballs and instruct your kids to hold the smaller ball on top of the basketball. Next, have them let go and watch in amazement as the basketball bounces up into the racquetball, transferring momentum as it makes contact! 

Learn more: Frugal Fun 4 Boys

22. Pumpkin Boats

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Wondering what to do with all those leftover pumpkins after Halloween? Look no further! Get your learners to make them into boats as they investigate the link between density and buoyancy. Support them to make differently-sized pumpkin boats and then make predictions about whether or not their pumpkin boat will sink or float.

Learn More: The Preschool Toolbox

23. How to Make a Hovercraft

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Hovercrafts were once something that only appeared in sci-fi stories, but now your kids will be making them in your classroom! Using simple household materials, they’ll learn how to harness the power of air resistance in this unique craft. Neat!

24. St. Patrick’s Day Balloon Rockets

physics is experiments

This holiday-themed activity is a great way to teach students about air resistance and acceleration! Your kids will craft their balloon rockets with a balloon, some tape, and a straw to keep it attached to the line. All that’s left is to let go to watch their balloon rockets blast off down the track! Why not make it competitive with a prize for the winning balloon of each race?

Learn More: Housing A Forest

25. Marshmallow Shooter

physics is experiments

Your learners will love this silly activity that incorporates a favorite sweet treat and a unique contraption! As they launch their marshmallows through the air, you can discuss how the force of the pull impacts the motion of the marshmallows.

Learn More: Teky Teach

26. Use The Force

physics is experiments

Star Wars fans will have fun with this one as they use “the force” to magically pick up paper clips! This exciting activity will have your kiddos wanting to learn more about magnetism and how it works! Simply have them place a large magnet on the back of their hand, reach toward a pile of paper clips, and watch as the paper clips magically fly into their hands!

Learn More: Rookie Parenting

27. Magic Toothpick Star Experiment

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You’ll have a tough time convincing your kids that this experiment shows physics at work and not magic! Have your kids take five toothpicks and snap them in half. Let them arrange them as shown, and then drip water in the middle of the sticks. They’ll be amazed as the water moves the sticks, seemingly mending them and creating a star!

Learn More: Living Life And Learning

28. Water Powered Bottle Rocket

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Bottle rockets are a fun science experiment to bring the science classroom outdoors . Your students will love learning about pressure and how it impacts the velocity of an item using just a recycled plastic bottle, a cork, some water, and a pump with a needle adaptor. To add even more excitement to this activity, let your kiddos decorate their own rockets!

29. Magnetic Levitation Activity

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With all these seemingly magical experiments, your kids are really going to wonder if you attended Hogwarts instead of a teacher-training college! Use the power of magnets to make a pencil float! Show your kids how to position their magnets so that they repel each other enough to suspend a pencil in mid-air! 

Learn More: Arvin D. Gupta Toys

30. Rubber Band Powered Car

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This adorable craft will teach your kiddos about force and motion! Let them spend some time going through a trial and error process to make a working car that’s powered by applying force to a  rubber band! Once they’ve got their models working, let them race to see whose creation goes the fastest and the farthest!

31. Making a Water Wheel

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Waterwheels have been around since Roman times, over 2000 years ago! Historically they were used in mills to grind grains into flour but nowadays they can be used as a source of renewable energy. Task your pupils with making a working waterwheel out of some simple household items like plastic cups, straws, and tape- are they up to the challenge? 

Learn More: Deceptively Educational

32. DIY Pulley Physics

physics is experiments

This pulley system will show your students that simple machines aren’t always so simple! Using whatever materials they can find and some string, they’ll need to create a fully functional, intricate pulley system along your classroom walls! This would make a great display for the entire school year!

Learn More: The Homeschool Scientist

33. How to Make an Orange Sink or Swim

physics is experiments

What is more likely to float, a peeled or unpeeled orange? Let your kids vote on this seemingly straightforward question then reveal the answer with a simple demonstration. Your students will watch in awe as they learn that they can change the density and buoyancy of an object by slightly altering it. In the case of the orange, however, the results might not be what they were expecting!

Learn More: Woo Jr.

34. Paper Airplane Test

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There’s nothing kids love more than making and throwing paper airplanes. If they’re usually banned in your classroom, then you might want to consider lifting that ban for one day! Turn this simple activity into an engineering investigation where your students will test out different designs to see which shape of the paper airplane will fly the furthest and which shape will stay in the air the longest! Physics made fun!

Learn More: Feels Like Home

35. Rising Water Experiment

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Water experiments in the classroom can be so much fun! This activity will teach your students how temperature and oxygen levels can affect the density of the air! All you’ll need are some matches, a cork, a plate of water, and a glass! They’ll love watching what seems like magic!

Learn More: Teach Beside Me

36. Physics Mystery Bag Challenge

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This unique physics activity will have your kiddos work in groups to solve a physics mystery. Each group will receive identical bags of mystery items and will be told what type of machine they need to create. The challenge is that there are no instructions! Using only the items in front of them and their ingenuity, your students will compete to see which group creates the best of the designated machine!

Learn More: Teaching Highschool Math

37. Solar Oven S’mores

physics is experiments

Fun science experiments are even better when combined with food! This solar oven teaches your students about how transmission, absorption, and reflection are used in a solar cooker to cook food. Your middle schoolers will be amazed at how easy it is to make yummy smores using an array of simple supplies, such as plastic boxes, aluminum foil, cotton, and glass.

Learn More: PBS

38. Laser Jello

Here’s another edible science project for your class! In this fun project, your kiddos will put the concepts of reflection and refraction into practice in a hands-on experiment. Give them some red and blue Jello to investigate how differently colored lasers project through it; they’ll be amazed as the Jello changes the lasers’ color and sometimes blocks out the light altogether! 

Learn More: Exploratorium

39. The Electric Butterfly

physics is experiments

Elevate the basic static-electricity balloon experiment by adding a paper butterfly! Teach your learners about positive and negative electrons by charging up the balloon with static electricity and using it to move the paper butterfly’s wings. This hands-on activity is a super way for them to see what can be a very abstract concept in action!

Learn More: CACC Kids

40. Homemade Thermometer

physics is experiments

This classic science experiment is great for showing how heat affects certain liquids by making them expand. Using the simple supplies of a bottle, cold water, rubbing alcohol, food coloring, a straw, and some modeling clay, have your students build their very own thermometer. As they heat or cool the surroundings, your kiddos will observe the liquid rising and falling in the straw!

41. DIY Electromagnet

physics is experiments

Creating an electromagnet is a cool way of combining middle-grade physics and engineering! This fun activity uses screws, some wire, and batteries to demonstrate how an electric current flows through metal to create a magnetic field. After this simple experiment, you can challenge your kids to take this activity to the next level and create bigger versions like their own electromagnetic cranes!

Learn More: Teach Engineering

42. Optical Illusion Fun

Experiments don’t get much cooler than optical illusions! You can use these amazing visual activities to teach your middle graders about how our eyes process light and send signals to our brains. Simply print out the template and let your kids add some color before they cut them out and attach them to a pencil. As they spin, they won’t believe their eyes! What a fun way to make this lesson about our eyes memorable!

43. Water Cycle in a Bag

physics is experiments

This cute little experiment is a great way to give your kids their very own visual of the water cycle! Print off the template and let your kids trace it onto their own Ziploc bag. All that’s left is to add water and tape it to a window where it’ll catch the sun! These little experiments are really quick to make and set up, but your kids will spend days analyzing them!

Learn More: Kiwi Co

44. Homemade Barometer

physics is experiments

Your students might have already made a DIY thermometer, but what about a barometer? You can help them learn about atmospheric pressure by crafting barometers using a jar or can, a balloon, a wooden stick, rubber bands, and some tape! As the weather changes over the next few days, so will the air pressure which will move the wooden stick of their barometers! Cool, right?!

Learn More: Easy Science For Kids

45. Basic Motor Mechanics

physics is experiments

It is amazing what you can do with some modeling clay, a magnet, a battery, and wire! This cool project showcases how electric energy works, demonstrating the interaction between the current and a magnetic field. This nifty little experiment will definitely get your students’ physics motors running! 

Learn More: Education

46. Xylophone fun

physics is experiments

Sound waves are much easier to teach and learn about when your kiddies can make visual connections. Have your learners fill empty jars with varying amounts of cold water (and a few drops of food coloring in each to make it look even more interesting) and then let them test the different pitches by hitting each one! 

Learn More: Sugar, Spice And Glitter

47. Build a Paper Bridge

This fantastic activity uses some really simple materials to challenge your kiddies to ‘build a bridge’. What seems like a pretty basic activity actually teaches them all about the scientific method and physics concepts behind building a bridge. They’ll learn about concepts like compression and tension to explain how bridges stay in place even under pressure! This is one your future engineers will love! 

48. Magnet Maze

physics is experiments

Art and physics are combined in this clever classroom experiment! Task your students first of all, with drawing a colorful maze on the outside of the bottle. Next, have them put in different items like coins, marbles, paperclips, and buttons to explore which ones they can attach the magnet to from the outside and navigate through their maze. A -maze- ing, right?!

Learn More: Science Museum Group

49. Super Sundial

physics is experiments

If you feel like taking your teaching outdoors, this sundial construction lesson is ideal! Bring some paper plates, bendy straws, and a pencil, and you’re good to go! Your learners won’t need a lot of background knowledge before the activity, but they’re sure to learn a lot about the Earth’s orbit and rotation in the process!

Learn More: Generation Genius

50. Sound Sandwich

physics is experiments

Your kiddies might initially be confused when you announce that they’ll be making sound sandwiches! Their confusion will soon turn to fascination at how such simple materials can make really interesting sounds! In this activity, they’ll be learning how to make music with sticks, straws, and rubber bands. See if they can figure out that it is the rubber band vibrating that makes the differently-pitched sounds!

51. Optical Lens Experiment

physics is experiments

Did you know that you can actually bend light? Your students will be surprised to learn this for sure! Through this investigation, you’ll teach them how when light goes from one medium to another (e.g. from air to glass), it usually bends. This series of simple activities covers the effects of convex and concave lenses on light, and thus how refraction works.

Learn More: Discover Primary Science And Maths

52. Density Tower floating experiment

physics is experiments

Combine the previously mentioned density tower and floating experiments in this cool activity! Using just a few simple ingredients that can be found around most homes, you can instruct your learners to combine cornstarch, vegetable oil, and rubbing alcohol. This will create the colored layers in this cool activity! Then they’ll add small items of their choosing to see which ones float in the various liquids, and at what density!

53. Walking Water experiment

physics is experiments

Capillary action isn’t a term that most of your kiddies will be familiar with but after doing this experiment they won’t forget it! Help your learners set up a row of cups with water and different colors of food dye. Next, they’ll add some strips of paper towels dipping each end into a different up and let them watch in amazement as the colored water seems to defy gravity and ‘walk’ up the paper and into the next cup!

Learn More: Made In A Pinch

54.  Build a Solar Still

physics is experiments

This easy experiment is the perfect way to demonstrate the water cycle and how sunlight can purify water. Start by letting your kiddos have a bit of fun to make ‘dirty’ water using assorted safe and edible kitchen ingredients. Then you’ll challenge them to make their own solar stills from plastic glasses, cling wrap, and, a bowl. Finally, they’ll set their glass of ‘dirty’ water inside the bowl, cover it with cling wrap, and then sit it out in the sun. And voila – clean water!

55. Slinky Sound Waves

physics is experiments

A metal slinky is a super simple but really effective source of demonstrating sound waves for your kids. Get two volunteers to hold the ends of the slinky and encourage your other students to take note of the different wave patterns when one or both of them shake it. This is a super way to make this abstract concept a little more visual for your class.

Learn More: Fizzics Education

56. Bike Wheel Gyroscope 

physics is experiments

Momentum is an important concept that your little physicists will cover in middle school science. A bike wheel gyroscope activity will amaze and enthrall your students as you use it to show off how the wheel’s mass and rotation obey the laws of angular momentum! The best part is that you’ll only need a bike wheel and some willing participants! 

Learn More: NASA

57. DIY Kaleidoscope

physics is experiments

Teach your kids all about the law of multiple reflections with this super fun, customizable activity! Using a cardboard tube, some mirrors, and small colorful items like confetti or sequins, these kaleidoscopes will be something they’ll always remember making. If you don’t have mirrors, why not try using aluminum foil instead? 

Learn More: Home Science Tools

58. Mapping Magnetic Field Lines

Teaching theoretical, intangible ideas is one of the hardest parts of teaching a subject like physics. Thankfully this short but practical activity makes this a whole lot easier by showcasing how the magnetic field lines of a bar magnet do not ever cross, are continuous, and go from north to south! All your kiddies will need is a magnet, a compass, and a marker!

59. Buzz Wire game

Electrical circuits can be really interesting to make, and this activity makes it fun too! Get your students to create their own ‘Buzz Wire’ game which will teach them about the loop system needed for electricity to work. Once they’ve made their loops, let them have a go at completing each others’ games! Can they get to the end without setting the buzzer off?

60. Galileo’s Gravity Experiment

physics is experiments

As the story goes, Galileo dropped two items from the Leaning Tower of Pisa to see which hit the ground first. Though we can’t be sure he actually did this, you can be sure that your students will have fun trying out this similar activity to learn about the effects of mass and air resistance on falling objects! Simply have them pick out two different objects, drop them from a height, and record which lands first!

Learn More: Science-Sparks

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Top 5 physics experiments you can do at home

October 17, 2022 By Emma Vanstone Leave a Comment

Physics is key to understanding the world around us. While some aspects may seem tricky to understand, many fundamental physics concepts can be broken down into simple concepts, some of which can be demonstrated using basic equipment at home.

This list of 5 physics experiments you can try at home is a great starting point for understanding physics and, hopefully a source of inspiration for little scientists everywhere!

Physics experiments you can do at home

1. archimedes and density.

The story behind Archimedes’ discovery of density is that he was asked by the King of Sicily to work out whether a goldsmith had replaced some gold from a crown with silver. Archimedes needed to work out if the goldsmith had cheated without damaging the crown.

The crown weighed the same as the gold the King had given the goldsmith, but gold is more dense than silver, so if there was silver in the crown its density would be less than if it was pure gold. Archimedes realised that if he could measure the volume of the crown, he could work out its density, but calculating the volume of a crown shape was a tough challenge. According to the story, Archimedes was having a bath one day when he realised that the water level rose as he lowered himself into the bathtub. He realised that the volume of water displaced was equal to the volume of his body in the water.

Archimedes placed the crown in water to work out its density and realised the goldsmith had cheated the king!

Density Experiment

One fun way to demonstrate density is to make a density column. Choose a selection of liquids and place them in density order, from the most dense to the least dense. Carefully pour a small amount of each into a tall jar or glass starting with the most dense. You should end up with a colourful stack of liquids!

Colourful density column made with oil, blue coloured water, washing up liquid, honey and golden syrup

2. Split light into the colours of the rainbow

Isaac Newton experimented with prisms and realised that light is made up of different colours ( the colours of the rainbow ). Newton made this discovery in the 1660s. It wasn’t until the 1900s that physicists discovered the electromagnetic spectrum , which includes light waves we can’t see, such as microwaves, x-rays waves, infrared and gamma rays.

How to split light

Splitting white light into the colours of the rainbow sounds tricky but all you need is a prism . A prism is a transparent block which is shaped so light bends ( refracts ) as it passes through. Some colours bend more than others so the whole spectrum of colours can be seen.

prism on a windowsill splitting light into it's constituent colours

If you don’t have a prism, you can also use a garden hose! Stand with your back to the sun, and you’ll see a rainbow in the water! This is because drops of water act like a prism.

3. Speed of Falling Objects

Galileo’s falling objects.

Aristotle thought that heavy objects fell faster than lighter objects, a theory that was later disproved by Galileo .

It is said that Galileo dropped two cannonballs with different weights from the leaning tower of Pisa, which hit the ground at the same time. All objects accelerate at the same rate as they fall.

If you drop a feather and a hammer from the same height, the hammer will hit the ground first, but this is because of air resistance!

If a hammer and feather are dropped somewhere with no air resistance, they hit the ground at the same time. Commander David Scott proved this was true on the Apollo 15 moonwalk!

Hammer and Feather Experiment on the Moon

Brian Cox also proved Galileo’s theory to be correct by doing the same experiment in a vacuum!

While you won’t be able to replicate a hammer or heavy ball and feather falling, you can investigate with two objects that are the same size but different weights. This means the air resistance is the same for both objects, so the only difference is the weight.

Take two water empty water bottles that are the same size. Fill one to the top with water and leave the other empty. Drop them from the same height. Both will hit the ground at the same time!

2 water bottles , one empty and one full of water for a Galilieo gravity experiment

4. Newton’s Laws of Motion

Sir Isaac Newton pops up a lot in any physics book as he came up with many of the laws that describe our universe and is undoubtedly one of the most famous scientists of all time. Newton’s Laws of Motion describe how things move and the relationship between a moving object and the forces acting on it.

Making and launching a mini rocket is a great way to learn about Newton’s Laws of Motion .

The rocket remains motionless unless a force acts on it ( Newton’s First Law ).

The acceleration of the rocket is affected by its mass. If you increase the mass of the rocket, its acceleration will be less than if it had less mass ( Newton’s Second Law ).

The equal and opposite reaction from the gas forcing the cork downwards propels the rocket upwards ( Newton’s Third Law ).

Mini bottle rocket made with a 500ml bottle

4. Pressure

Pressure is the force per unit area.

Imagine standing on a lego brick. If you stand on a large brick, it will probably hurt. If you stand on a smaller brick with the same force it will hurt more as the pressure is more!

Snowshoes are usually very wide, this is to reduce the pressure on the snow so it sinks less as people walk on it.

Pressure equation. Pressure is force divided by area

Pressure and Eggs

If you stand on one egg, it will most likely break. If you stand on lots of eggs with the same force, you increase the area the force is applied over and therefore reduce the pressure on each individual egg.

child standing on eggs with bare feet

That’s five easy physics experiments you can do at home! Can you think of any more?

Old blackboard with Einsteins equation written in chalk

Last Updated on March 27, 2023 by Emma Vanstone

Safety Notice

Science Sparks ( Wild Sparks Enterprises Ltd ) are not liable for the actions of activity of any person who uses the information in this resource or in any of the suggested further resources. Science Sparks assume no liability with regard to injuries or damage to property that may occur as a result of using the information and carrying out the practical activities contained in this resource or in any of the suggested further resources.

These activities are designed to be carried out by children working with a parent, guardian or other appropriate adult. The adult involved is fully responsible for ensuring that the activities are carried out safely.

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10 Physics Experiments That Changed Our View Of the Universe

Some experiments yeilded results so profound they changed out view of the cosmos forever

No one can question the impact of science on human civilization, and the importance of experimentation in science is equally undeniable. Some experiments confirm what we already know, others suggest a mechanism by which observed phenomena are driven.

For the latter type of experiment think of ancient Greek polymath Archimedes in the bathtub realizing that the displacement of water was directly related to the volume of an object placed in it, which legend suggests led to him running down the street naked yelling "Eureka!" —  something we now know probably didn't happen.

Most scientific research is based on investigating "known unknowns" — scientists observe something, develop a hypothesis to be tested, and then design experiments to test this. But other experiments have a more profound effect on our understanding, suggesting things we had no idea about — the "unknown unknowns."

Throughout the history of science, there have been experiments in all the major disciplines that have delivered paradigm-shifting or even status quo-shattering results.

But when it comes to our understanding of the Universe arguably no field of science has delivered more results that fundamentally shifted our understanding of the universe than physics — encompassing astronomy, perhaps the earliest science, particle physics, nuclear physics, cosmology, and quantum mechanics. Some experiments are performed physically, while others are performed hypothetically in some of history's greatest minds.

These physics experiments fundamentally changed how we view the universe and our place within it.

The Earth moves from the center of the Universe

The idea that the Earth orbits the sun along with the rest of the planets may not seem particularly controversial, but the fact that we do not occupy a unique perspective or privileged position in the universe caused major waves in the 1600s when it finally began to gain traction.

Though the concept of a spherical Earth revolving around a "central fire" had planted the seeds of heliocentrism as early as the 5th Century BC via the musings of philosophers Philolaus and Hicetas, something extended upon by Aristarchus of Samos two centuries later, from the 2nd Century AD scientific thought had been dominated by the geocentric, or Earth-centered, theory of Claudius Ptolemy of Alexandria .

This would be the case for almost 1,400 years until the publication of Nicolaus Copernicus's De revolutionibus orbium coelestium libri VI or "Six Books Concerning the Revolutions of the Heavenly Orbs" in 1543, which put heliocentrism back on the table.

It was Italian natural philosopher, astronomer, and mathematician Galileo Galilei that would make the experimental steps that saw the so-called Copernican model of a sun-centric solar system eventually accepted as the accurate version of space at a local scale.

In 1610, using his telescope Galileo observed the planet Venus , discovering that it has phases just like the moon.

Galileo reasoned that these phases could only be explained by Venus going around the sun, upon occasion passing behind and beyond our star rather than revolving around the Earth.

The concept that the Earth was not the center of the cosmos would enrage the church which believed it contradicted scripture. This led to the inquisition process being brought against Galileo resulting in him being gagged against speaking on or writing about heliocentrism.

The nature of color: Netwon splits light

Though Sir Issac Newton's laws of motion and his contributions to the theory of gravity are widely regarded as his crowning achievements, the great passion of the author of Principia Mathematica was optics.

In the early 17th Century, when optics was growing as a field in physics with the development of instruments like the microscope, Newton decided to investigate the nature of light, in turn discovering how color arises.

The experiment devised by Newton to do this was devilishly simple. The physicist pushed a small pinhole through his blinds to allow a small beam of sunlight through. He found that when refracted by a prism this light changed into an oblong made up of different colors. Newton found that no matter the shape or size of the hole he cut and thus the shape of the beam of sunlight, the refracted light remains an oblong block of the same colors in the same order.

Even more surprisingly, he found that if he introduced a second black he could change the rainbow back into white light.

This showed white light from the sun was made of a miscellany of different colors. Delving deeper still, Newton found that red or blue light, when refracted by a prism, remained unchanged.

Perhaps the most important discovery this experiment yielded was the fact that the angle of the refraction of light depended on its color, the first hint that colors of light have their own frequency and wavelength.

To the heart of the atom: The Geiger-Marsden experiment

The concept of an atom — the point at which matter cannon longer be cut — dates back to the ancient Greeks, with the word itself derived from the Greek word "atomos" meaning "indivisible." Until 1897, scientists believed that atoms had no internal structure and were the smallest units of matter. That was before the discovery of a small negatively charged particle — the electron — by Joseph John Thomson.

In 1904, J.J Thomspon suggested that these particles were embedded in a positively charged substance much like fruit dispersed in plum pudding in his appropriately named plum-pudding model of the atom.

This model was overturned by the Geiger-Marsden experiment , also known as the gold foil experiment or the α-particle scattering experiments, pioneered by Ernest Rutherford and conducted by his protégés, Ernest Marsden and Hans Geiger.

Firing α-particles — which we now know are identical to a helium-4 nucleus — emitted by a radioactive source at a thin sheet of gold foil Rutherford reasoned that if the plum-pudding model of the atom was correct these traveling particles would experience the tiniest of deflections. This is due to the fact that an α-particle is about 7,000 times more massive than an electron.

The 1911 experiments showed that occasionally α-particles experienced a large deflection. While only one in 20,000 alpha particles had been deflected 45° or more this was enough to spark a major rethink of the atom and unveiled the presence of the atomic nucleus. 

Rutherford compared the results to firing a 15-inch shell at a sheet of tissue paper and having it bounce back directly at you!

This revealed that the majority of the matter in an atom was concentrated at its center. Rutherford proposed a model of the atom with electrons orbiting a massive positively charged nucleus.

This model in time would be overturned, but it represented a vital step in discovering the proton and the neutron and unveiling atomic structure.

The Twin Paradox: Time is relative (so is space)

For Newton, the concept of space was fairly simple. A stage upon which the events of the Universe simply unfold. But, over the course of the first two decades of the 20th Century, Albert Einstein would shatter the notion of prosaic space, showing space itself to be a player in the events of the Universe, both directing the action and being influenced by other actors such as mass. This in itself would have been revolutionary, but Einstein didn't stop there, he showed time and space to be a single entity with the 4th dimension of time just as subject to change as space depending on the circumstance of the observer.

While Einstein became a master of the Gedankenexperiment — or thought experiment  — to develop the theory of special and then general relativity, there is one thought experiment above all others that perhaps best exemplifies Einstein's groundbreaking approach to time, the so-called "twin paradox."

The twin paradox expresses the idea that "moving clocks run slow" and the concept of time dilation. It imagines twin sisters — Terra and Astra — the latter of whom blasts off from Earth in a rocket headed for a distant star system. Terra waits on Earth and from her reference frame, she will see Astra's moving clock running slow. 

But, here's where the paradox element is introduced.

The paradox element

In Astra's reference frame, it isn't her clock that is moving, it's Terra's. That means she sees Terra's clock running slower than hers. So the question is, who is right? When the sisters meet up again upon Astra's return to Earth after many years, who is older?

The sisters discover that Terra has aged while Astra has retained her youth, and the reason for this is one of the key aspects of special relativity, it only applies to non-inertial reference frames — reference frames that don't accelerate. During Astra's trip through the cosmos, there are various times when she has to accelerate, which also includes changing directions.

The difference in age between Terra and Astra depends on factors such as her speed, how long she was away, and how many times she had to change speeds or directions.

The effect of time dilation is no longer restricted to thought experiments. Physicists have measured its effect on short-lived called Muons. When created by cosmic rays hitting the upper atmosphere these particles should exist for just 2.2 microseconds. Even when factoring in time dilation and the incredible velocity of muons–-0.98c or 98% the speed of light–-very few of these particles should survive long enough to strike the surface of our planet. But thanks to time-dilation, just like Astra retaining her youth, many of these particles do survive long enough to reach the surface of the planet.

What is light? The double-slit experiment

The splitting of light as it passed through a prism was the beginning of our investigation into this fundamental aspect of reality. For decades the argument raged amongst physicists as to whether light was a particle or wave. The double-slit experiment proved light is neither a particle, nor a wave, but has properties of both.

The double-slit experiment begins with monochromatic light — light of one wavelength and thus color — shining through two slits with a width separated by a distance similar to its wavelength. 

As the wave passes through both slits, it splits into two new waves — just like water waves do as they encounter a rock. These two waves then interfere with each other, where a peak meets a trough, they will cancel each other out — so-called destructive interference. However, where a peak meets a peak the waves are reinforced — constructive interference — and the points with the brightest light. 

On a second wall behind the screen, the light creates a stripy pattern, called an interference pattern. This demonstrates the wave nature of light, but there is more to this experiment.

If the light sent through the slits is reduced in intensity to one photon at a time, we see a particle-like distribution building on the screen. But, as the particles pile up, an interference pattern begins to build up like the photons are interfering with themselves. 

This demonstrated that while a photon was detected as having the properties of a particle, interference unique to a wave appeared passing through the double-slit, thus revealing that the photon has properties of a particle and a wave.

Particle wave daulity in matter: The double-slit experiment part 2

Physicists weren't done with the double-slit experiment. It had already revealed the particle-wave duality of light, but researchers were determined to run the experiment with another particle , replacing light with electrons — tiny negatively charged fundamental particles of matter. 

Using an electron gun to fire particles through the double-slit portion to a fluorescent screen or another type of particle detector, the electrons seem to appear randomly.

As more electrons come through the slits, an interference pattern — bands of dark "hits" and light misses — develops just as we see with the photons implying that the electrons are traveling just like photons do — like waves.

This interference pattern disappears if the experiment is run again, but this time with one of the slits closed, which leads to a pile-up of hits on the screen just like we would expect with bullets.

Re-rerunning the experiment with both slits open and the electrons dripping through one at a time we find that the interference pattern begins to emerge again. This implies that like the photons the electrons are interfering with themselves as they pass through the double slits.

The consequence of this is we were forced to abandon the classic idea of a particle possessing a single defined trajectory through space. The particle can be considered passing through each slit causing constructive and destructive interference. It also shows that matter — like light — exhibits particle-wave duality .

Quantum Entanglement: Investigating spooky action at a distance

Any scientific phenomenon that stunned Albert Einstein must be revolutionary. The concept of entanglement is the idea that two particles can be linked in such a way that changing one instantly changes the other. But, what troubled Einstein was the fact that this change would happen instantaneously even if the particles are at opposite ends of the Universe.

This challenges the ideas in physics of local realism — the concepts that the cause of a physical change must be local and that the properties of objects are real and exist in our physical universe independent of our minds. These challenges led Einstein to describe entanglement as "spooky action at a distance" and resulted in him spending the last years of his life devising thought experiments that would show the theory of quantum physics was incomplete with hidden variables explaining the nature of entanglement.

A physical experiment would finally validate the non-local nature of entanglement. In the 1960s physicist, John Bell devised a test called Bell's Inequality to hunt for hidden variables.

The aim was to test three assumptions; locality, realism, and freedom of choice — the idea that physicists can make measurements freely without the influence of hidden variables. Experiments to test Bell's Inequality have shown that when particles are entangled, the outcomes of measurements are more statistically correlated than would be expected in non-quantum systems described by classical physics.

Most physicists believe that entanglement violates either the first or second principle of Bell's Inequality. What is certain is that a change in an entangled particle causes an instantaneous change in its partner.

The cat, the box, and the poison

The rules of the subatomic world described by quantum physics are weird. Scientists would describe this as counterintuitive and perhaps one thought experiment above all others perfectly exemplifies this weirdness.

In quantum mechanics, the physics of the very small, possible states of a system is determined by wave functions that can overlap. This means that a quantum system modeled by waves can be described as existing in multiple states at one time — a  superposition  — with these states collapsing and taking a single value when measured or forced to interact with another system.

Part of what is known as the Copenhagen interpretation of quantum mechanics, Erwin Schrödinger wanted to show the flaws in this theory and inadvertently created one of the most talked-about thought experiments of all time — Schrödinger's cat.

Schrödinger suggested placing a cat in a box with a diabolical device — a vial of deadly poison that would break upon the decay of an atomic nucleus. Because the decay of an atom is a completely random process, there is no way of determining if this has happened without opening the box.

That meant that if we treat the box as a quantum system, Schrödinger's cat is in the ultimate superposition — being both dead and alive at the same time. The situation would only resolve upon the opening of the box when the wavefunction of the system collapses and the cat is found to be either dead or alive.

What is the Cosmic Microwave Background?

The cosmic microwave background (CMB) is radiation left over from an event shortly after the big bang called " the last scattering ." This was the point, around 14 billion years ago, at which the Universe had cooled enough to allow electrons to join protons to form the first atoms.

As a consequence of this, photons were no longer endlessly scattered by free electrons and were suddenly permitted to freely travel the Universe. In other words, the Universe went from opaque to transparent. Radiation from this point should have a uniform temperature and some by spread through the Universe in a highly-uniform way.

Until 1965, Bob Dicke and his Princeton University team had been diligently searching for evidence of this "cosmic fossil" frozen into the Universe. But, unbeknownst to them, another team, just 50 or so miles away in New Jersey had already detected the CMB, they just didn't know it yet.

Astronomers Arno Penzias and Robert Wilson were having problems with the Holmdel Horn Antenna – a microwave radio telescope and satellite communication system–at Bell Labs. The duo was attempting to use the sensitive instrument to search for hydrogen in the Milky Way but they were picking up the same buzz from all areas of the sky. The duo attempted to rid themselves of this "background noise" several times trying to limit everything that occurred to them that could be the cause of this static.

Diving deeper

This involved eliminating badly insulated wires and even involved crawling into the horn-shaped antenna to remove what they described as "white dielectric material"–pigeon droppings to you and me–left by roosting birds. Penzias and Wilson finally determined that the signal was not coming from Earth. It was only when communicating with Dicke at Princeton that Penzias and Wilson realized what they had found. After a brief phone conversation with the Bell Labs team, Dicke's words to his team said it all: "Well, boys, we've been scooped."

Arno Penzias and Robert Wilson would share the 1978 Nobel Prize in Physics for their discovery of the CMB with Pyotr Leonidovich Kapitsa "for his basic inventions and discoveries in the area of low-temperature physics.

We now know the CMB fills the Universe with a uniform temperature of 2.7 K–less than three degrees above absolute zero, and at one point bits effects could be seen in every living room in the U.S. According to NASA , the CMB was "responsible for a sizeable amount of static on your television set–well, before the days of cable. Turn your television to an "in-between" channel, and part of the static you'll see is the afterglow of the big bang."

The CMB revealed conclusively that the Universe had undergone a period of rapid expansion in its early history confirming the Big Bang model of cosmology beyond doubt. But the expanding Universe was yet to deliver its greatest blow to our understanding of the cosmos.

What is dark energy? The Universe is expanding... and it's accelerating

At the beginning of the 20th Century, Edwin Hubble discovered from the observed relation between distance and recession velocity of galaxies that the universe is expanding.

Until 1929 , and the publication of Hubble's short paper, "A relation between distance and radial velocity among extra-galactic nebulae," the common consensus in science was that the universe was static and unchanging. Albert Einstein had even added a factor called the cosmological constant — represented by the Greek letter Lambda — into his equations of the universe to ensure it remained static.

But, if this revelation was a surprise to the scientific community, the discovery in 1998 that this universal expansion is accelerating came as a complete shock. To see why this is, imagine giving a swing a push and then watching it gradually slow. As it is about to stop suddenly it begins to speed up again, accelerating despite no added force.

That's what the findings from astronomers that examined distant type Ia supernova — known as "standard candles" because of how their uniform light output makes them excellent distance measures — imply is happening with the Universe. Despite slowing after the initial rapid expansion of the Big Bang, the very fabric of space is again accelerating in its expansion.

This led to the introduction of " dark energy " as a placeholder for whatever force is driving this accelerating expansion. Independently confirmed since the initial supernova observations, NASA now estimates dark energy to account for 68 percent of the Universe's matter/energy content.

And the effect of dark energy is now described by the reintroduced cosmological constant  — still represented by lambda — rescued from the science dustbin with a new purpose.

Infinite Worlds: Discovering exoplanets

For as long as humanity has known that the stars are bodies just like the sun we have wondered about the planets that could orbit these distant stellar bodies and if they could potentially harbor life just as Earth does.

Yet, despite astronomy's long history and its status as arguably the first science, the discovery of the first planet outside the solar system — an extrasolar planet or exoplanet — would take until the end of the 20th century.

Two major "firsts" in terms of exoplanet discoveries both occurred in the 1990s. In January 1992 astronomers Dale Frail and Aleksander Wolszczan announced the discovery of two rocky planets and a possible third orbiting a pulsar —  PSR B1257+12  — located almost 2,000 light-years from Earth.

Pulsars are rapidly rotating neutron stars and blast out powerful radiation, meaning that the three planets around PSR B1257+12 could not possibly support life.

The discoveries will continue

In 1995, Michel Mayor and Didier Queloz discovered 51 Pegasi b  — a so-called hot Jupiter exoplanet so close to its star that it has a scorching hot surface temperature of 1,000–1,800 degrees Fahrenheit and completes an orbit in just four days.

The duo, who shared the 2019 Nobel Prize in Physics for the discovery, located the planet using a detection method called the radial velocity technique . This measures the tiny wobble that an orbiting planet causes in its host star. The tiny movement causes a slight shift in the wavelength of light emitted by the star.

This makes light from the star redder if it is tugged away, or bluer if it is tugged towards Earth, which astronomers can use to infer the presence of a planet.

Since the discovery of the first exoplanet humanity hasn't looked back. NASA's exoplanet catalog now numbers over 4,800 confirmed worlds beyond the solar system — a testament to the power of detection methods that can pinpoint the tiniest of signals.

Of these, NASA says 927 planets have been discovered using the radial velocity method. This makes it the second most successful exoplanet detection method after the transit method — which measures tiny dips in light as a planet passes across the face of its star — which has been used to find 3854 exoplanets according to NASA.

With the event of the James Webb Space Telescope (JWST) the golden age of exoplanet science has truly begun.

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Virtual Physics Experiments: Learn Everything About Digital Experiments

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Physics is a fascinating subject that deals with nature’s basic laws. One of the best ways to learn physics is by doing experiments. Traditionally, students performed these experiments in a physical laboratory setting. This is where virtual physics experiments come in. Virtual physics experiments are computer simulations of real-world physics experiments.

In this blog, we will explore the world of virtual physics experiments. We will also delve into the benefits of using advanced digital physics simulations in the learning process.

Challenges and problems faced by students in physics laboratory

physics

Before delving into virtual experiments, it is essential to understand the challenges that students often face in physical physics laboratories:

  • Limited Equipment Availability: Many schools and colleges have limited resources, resulting in inadequate equipment for conducting experiments. This scarcity often forces students to share equipment, limiting their hands-on experience.
  • Time Constraints: Physical labs often have strict time constraints. Students may have only a limited time to complete experiments, which can lead to rushed or incomplete observations.
  • Safety Concerns: Physics experiments can involve dangerous elements, such as high voltages or chemicals. Ensuring the safety of students in a physical lab is a constant concern for instructors.
  • Inadequate Supervision: In a crowded lab with limited instructors, it is challenging for each student to receive personalized guidance and supervision. This can hinder their understanding and ability to perform experiments correctly.
  • Equipment Malfunction: Mechanical and electrical equipment can malfunction, disrupting experiments and causing frustration for students.
  • Resource Constraints: Many schools struggle to maintain and upgrade their lab equipment due to budget constraints, leading to outdated or non-functional apparatus.

Benefits of advanced digital physics simulations

physics lab

Now, let’s explore how advanced digital physics simulations address these challenges while offering numerous benefits:

  • Accessibility: Virtual experiments eliminate the constraints of physical laboratories, making them accessible to students regardless of their geographical location. This is especially beneficial for students in remote areas or those with limited access to laboratory facilities.
  • Safety: Dangerous experiments involving high voltages or hazardous materials can be simulated safely in a digital environment, reducing the risk to students and instructors.
  • Unlimited Resources: Virtual simulations provide an almost limitless array of resources and equipment, allowing students to perform experiments with various parameters and conditions, enhancing their understanding of underlying concepts.
  • Instant Feedback: In virtual experiments, students receive immediate feedback, enabling them to rectify mistakes and gain a deeper understanding of the experimental process.
  • Cost-Efficiency: Setting up and maintaining a physical laboratory can be expensive. Virtual experiments reduce costs associated with equipment, maintenance, and consumables.
  • Time Efficiency: Digital simulations save valuable class time that would otherwise be spent setting up and conducting experiments, allowing educators to cover more content.
  • Enhanced Visualization: Virtual experiments often come with advanced graphics and animations, making it easier for students to visualize complex physical phenomena.
  • Customization: Students can repeat experiments multiple times with different parameters, reinforcing their learning and experimentation skills.

How are these virtual physics experiments developed?

Ever wondered how these experiments are created? Creating digital and virtual physics experiments involves the application of various scientific principles and technologies to simulate physical phenomena and interactions in a computerized environment. Let’s know the science and development process behind digital and virtual physics experiments.

  • Understanding the Physics: Developers must have a deep understanding of the physics principles they want to simulate.
  • Mathematical Modelling: Physics simulations often begin with mathematical models that describe the behaviour of physical systems. These models use equations, such as Newton’s laws of motion or Maxwell’s equations for electromagnetism, to represent the underlying physics.
  • Programming Languages: Virtual physics experiments are implemented through computer programming using languages like C++, Python, or Java. These languages are chosen based on factors such as efficiency, platform compatibility, and ease of development.
  • Simulation Engines: Developers often use specialized simulation engines or libraries that provide tools and functions for modelling and solving physics problems efficiently. Examples include Unity for game-based simulations and libraries like OpenFOAM for fluid dynamics simulations.
  • Rendering and Graphics: The visual representation of the virtual experiment is crucial. Developers use computer graphics techniques to render 2D or 3D simulations, including the use of shaders, textures, and lighting to create realistic visuals.
  • User Interface (UI): A user-friendly interface is designed to allow users to interact with and control the simulation. This includes features like menus, buttons, sliders, and data visualization tools.
  • User Input: Users interact with virtual physics experiments through input devices like a keyboard, mouse, or touchscreen. These inputs are translated into actions within the simulation, such as applying forces, changing parameters, or adjusting settings.
  • Real-Time Computation: Physics simulations must run in real-time, providing instantaneous feedback to users as they interact with the virtual experiment. Achieving real-time performance often requires optimizing code and using parallel computing techniques.
  • Accessibility and Educational Goals: Digital and virtual physics experiments are often developed with specific educational goals in mind. Developers must consider the target audience and design experiments that align with educational objectives
  • Integration with Hardware: In some cases, virtual physics experiments can be integrated with hardware devices like sensors, haptic feedback devices, or virtual reality (VR) headsets to enhance the user experience and provide more realistic interactions.

Experiments in the physics curriculum

Different state boards mandate a set of physics experiments for students. These experiments cover a wide range of topics, including mechanics, electricity, optics, and modern physics. There are many different virtual physics experiments available online. With virtual physics experiments, students can now access a vast repository of experiments that closely mimic real-world scenarios. Some of the most well-known are:

  • Simple Pendulum Experiment: This experiment allows students to study the period and frequency of a simple pendulum.
  • Ohm’s Law Experiment: By virtually connecting resistors, ammeters, and voltmeters, students can explore Ohm’s law and understand the relationship between voltage, current, and resistance.
  • Focal Length of Concave and Convex Mirror: Digital simulations allow students to adjust the object’s position and observe the corresponding image formed by the mirror, helping them understand the concepts of focal length and mirror behaviour.
  • Characteristics of a PN Junction Diode: Virtual experiments allow students to alter diode properties by adjusting the voltage and monitoring how it affects the flow of current, which aids in the understanding of semiconductor physics.

These are just a few examples of the many virtual physics experiments that are available. One of the most effective virtual science labs available in the market is SimuLab.

The most effective virtual experiment simulations and virtual lab – SimuLab

SimuLab is a 3D virtual scientific laboratory that enables students to study and conduct experiments – anytime, anywhere. It has the most advanced simulations of K-12 science subjects. SimuLab is an excellent tool for anyone who wants to experience real experiments or learn more about science. It is a cutting-edge learning tool created by IITians using modern technologies such as AI, AR, and VR.

physics laboratory

  • Easily access the science laboratory with convenience and without any difficulties.
  • Acquire a simplified and engaging method to learn scientific experiments.
  • Receive comprehensive, step-by-step instructions for conducting experiments.
  • Foster the development of scientific reasoning and a strong conceptual grasp of the subject.
  • Practice experiments an unlimited number of times.
  • Retain a deep understanding of scientific concepts over an extended period.
  • Achieve improved academic performance and excel in competitive exams such as IIT/NEET.
  • Access the platform effortlessly across various devices, including smartphone, desktop, and tablet.

About virtual simulations:

Abundant resources are available to facilitate a comprehensive understanding of each science experiment .

  • Aim: Establishes a clear focus on the experiment’s purpose and objectives.
  • Objective: Outlines what will be taught, how it will be learned, and what outcomes can be expected from the experiment.
  • Safety Precautions: Provides safety guidelines specific to each experiment to ensure a secure laboratory environment.
  • Theory: Offers simplified theoretical explanations to aid learners in grasping fundamental concepts.
  • Story: Incorporates real-life scenarios related to the subject to enhance engagement in the learning process.
  • Simulation: Grants access to an advanced virtual platform for conducting science experiments.
  • Quizzes: Includes multiple quiz questions to facilitate better preparation for competitive exams like IIT/NEET .
  • Analytics: Allows users to assess their progress and monitor overall progress using a performance dashboard.

virtual experiments

Final words

Virtual physics experiments have transformed the way students learn and understand physics concepts. For students, these simulations offer a comprehensive and efficient way to conduct experiments while addressing the challenges faced in physical laboratories. Embracing virtual physics experiments not only keeps students engaged but also prepares them for a world where technology plays an ever-increasing role in scientific research and experimentation.

Writer – Girish Hedau

Scientific Content Writer – Physics

September 28, 2023

Previous Virtual Chemistry Experiments: All that You Need to Know

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Ultracold four-atom molecules are bound by electric dipole moments

Weakly bound tetratomic molecules that are more than 3000 times colder than any previous four-atom molecules have been created using a newly developed “electroassociation” technique. The work, which is based on a 2003 proposal, could make it possible to assemble even larger molecules at ultracold temperatures, open up studies in superfluidity and superconductivity, and even find applications in quantum computing.

In 2003, theoretical physicist John Bohn of JILA in Boulder, Colorado was part of a team led by the renowned experimentalist Deborah Jin , who died in 2015. They were studying the effects of magnetic fields on ultracold fermionic gases. The researchers discovered that the atoms formed weakly bound diatomic molecules when they tuned the value of the field across a so-called Feshbach resonance at which the binding energy was equal to that of the molecules. This process subsequently became known as magnetoassociation.

Then, in 2008, a team led by Jin and her University of Colorado colleague Jun Ye demonstrated the conversion of these fragile dimers into ground-state molecules using a three-level laser cooling technique called stimulated Raman adiabatic passage (STIRAP). The two techniques have subsequently been used by countless other groups to create ultracold dimers for a plethora of applications such as the study of quantum chemistry.

Magnetoassociation only works, however, on particles with magnetic dipole moments – which means they must have unpaired electrons. Jin’s group was working with potassium atoms, which are magnetic. Once they associate to form diatomic potassium molecules, they no longer respond to magnetic fields.

Why not electroassociation?

In the same year, Bohn and colleague Aleksandr Avdeenkov published a theoretical paper suggesting that it might be possible to induce non-magnetic molecules to pair up if they had an electric dipole moment: “Magnetoassociation was something that existed, so we thought, well, why not electroassociation?” says Bohn, “We didn’t give it any more thought than that.”

In 2023, however, using a modified version of Bohn’s original proposal, Xin-Yu Luo of the Max Planck Institute for Quantum Optics in Germany and colleagues placed strongly bound, ultracold sodium potassium molecules (produced by magnetoassociation and STIRAP) in an oscillating external microwave field. At specific field values, they found spectroscopic evidence of a resonant state unlike anything previously seen between pairs of molecules. In this state the two molecules danced in parallel as their own electric dipole moments modified the applied potential. The resulting interaction was repulsive at short distances but attractive at long distances, resulting in a bound state that was about 1000 times larger than the diameters of the individual molecules. At the time, however, the researchers only had evidence that the state existed – not any controlled means to place particles into it.

Circularly polarized microwaves

In the new work, the Max Planck researchers and colleagues at Wuhan University in China found that, by applying a circularly polarized microwave field to sodium potassium molecules at temperatures around 100 nK before increasing the ellipticity of the field, they could induce some of them to form tetramers. The team also managed to dissociate the tetramers and, by looking at the shape of the dimers released, image the tetramer wavefunction. They describe this in Nature .

“The binding energy is radio-frequency scale,” says Luo, “It’s more than 10 orders of magnitude weaker than typical chemical bond energy.”

The researchers now hope to use STIRAP to create strongly bound tetramers. This will be no easy task, says Luo, because it requires a suitable intermediate energy level, and tetramers have many more energy levels than dimers. “Even for me it’s an open question whether we can find a suitable state in the forest of energy levels,” says Luo. If they can, however, it holds out the tantalizing possibility of repeating the technique to build ever-larger molecules.

optical components on an optical bench, bathed in orange light

Entangled molecules make a novel qubit platform

The researchers are also looking to cool their molecules further into a Bose–Einstein condensate (BEC). They would then become a powerful tool for studying the crossover between the BEC state and the Bardeen–Cooper–Schrieffer (BCS) state of superconductivity. This crossover is crucial to understanding high-temperature superconductivity. Such a tool would allow physicists to tune the constituents of the condensate between fermionic dimers and bosonic tetramers simply by tuning the microwave field. This would allow them to turn a BEC into a degenerate Fermi gas that supports Cooper pairs.

Further into the future, the system could even be useful in quantum computing as theoretical predictions suggest it should support topologically protected Majorana zero modes that could be used to create noise-resistant qubits.

Bohn describes the work of Luo and colleagues as fantastic, adding “Not only is it well done, but it’s something that a lot of people have been hoping for for a long time.” After reading the group’s 2023 paper, he collaborated with two colleagues to develop a theoretical framework, described in Physical Review Letters in July 2023, for achieving electroassociation based on the group’s results, and showing the ideal rate at which to alter the fields. “While we were doing that, they already did the experiment,” he says; “Evidently they figured that out just fine on their own.”

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