How do astronomers know what wavelength the body will emit when it is at rest?

How is Doppler redshift of distant galaxies established?


Intuitive analysis of gradient, divergence, curl


Can we detect a gravitation field of an object after it failed into a black hole?

Behavior of a gravitation field of an object falling into a black hole


Since voltage determines an electron's energy, why is it current rather than voltage that is harmful?

What causes an electric shock - Current or Voltage?


Special relativity time dilation - what will the outcome be?


Why won't heat make the inner radius shrink to free up space?

Will a hole cut into a metal disk expand or shrink when the disc is heated?


What happens when yellow light is passed through a prism?


How is momentum conserved in this example?


Are there two roots for time in projectile equation because the projectile ascends & descends?

What do negative times and negative displacements represent in parametric projectile equations?


The Time Freezing Room - Theoretically possible?


What accounts for the flow of liquid, Net force or Net Pressure?

What force accelerates a liquid moving in a narrowing pipe?


How stable is a tablespoon of neutrons once removed from a neutron star?

What would happen to a teaspoon of neutron star material if released on Earth?


What is the implication of an expanding universe on a small scale?

Why does space expansion not expand matter?


Why does vacuum have a nonzero characteristic impedance towards electromagnetic radiation?


Why don't electromagnetic waves require a medium?


Problem understanding Lorentz invariance

Proving the Lorentz invariance of the Lorentz invariant phase space element


Why does accelerating electron emits photons?

How EM waves are produced by accelerating charged particles?


Is there Sun constantly falling (and us along with it)?

Does the curvature of spacetime theory assume gravity?


Photograph of Light as Wave and Particle

Have they really photographed light behaving both as a particle and a wave?


If I run along the aisle of a bus traveling at (almost) the speed of light, can I travel faster than the speed of light?


Sign of reflection coefficient $E_r/E_i$ at normal incidence!

Phase difference in reflection coefficient between S and P polarisation at normal incidence?


Is the universe fundamentally deterministic?


Advanced (undergraduate) book on electromagnetism

Recommended books for advanced undergraduate electrodynamics


Coherence of waves - phase difference constant OR frequency the same?


Where does the extra kinetic energy of the rocket come from?


Are there software for drawing Feynman diagrams easily?

What software programs are used to draw physics diagrams, and what are their relative merits?


Why there is a $\frac{1}{2}$ in the distance formula $d=\frac{1}{2}at^2$?


When one blows up a latex balloon, why does it get easier to blow once it has a little air in it (after 1 or 2 breaths)?

Why is filling a balloon from your mouth much harder initially?


Why does Bohr's stationary orbits not radiate energy?

Why do electrons occupy the space around nuclei, and not collide with them?


Can an object have 0 acceleration because its instantaneous velocity is 0?

How can an object's instantaneous speed be zero and it's instantaneous acceleration be nonzero?


Where would reddish purples lie on the spectrum of light, considering red light and purple light are on opposite ends of the visible spectrum?


/HVAC/ Air speed and influence on human body


Does energy expenditure require movement?

Why does holding something up cost energy while no work is being done?


If you have two Planck lengths extended from one point forming a right angle, whats the length of the hypotenuse?

Does the Planck scale imply that spacetime is discrete?


Does a body always rotate purely about its center of mass?

Do objects rotate around the torque vector or its center?


How does permanent magnets attract each other if the $B$-field can do no work?

How can magnets be used to pick up pieces of metal when the force from a magnetic field does no work?


How does a physical knock initiate freezing of supercooled water?


Is there proof gravity bends space or is it just the most convenient explanation?

General relativity: is curvature of spacetime really required or just a convenient representation?


Is the electron of carbon identical to that of hydrogen? How to prove it?


Would it be ok to say that not all light travels at the same speed when you consider its own perspective?

Does a photon in vacuum have a rest frame?


Can a free particle absorb/emit photons?


Why not 2, 3, 4, or more photons can be absorbed by single electron?

Photoelectric Effect, Why can't two quanta interact with an electron at the same time?


How does a bikerider turn by leaning on one side?

Does leaning (banking) help cause turning on a bicycle?


What is the form of energy that is forming while lifting a suitcase

Why does holding something up cost energy while no work is being done?


Is there a Lorentz invariant approximation to General Relativity?

What different approximations yield Gravitoelectromagnetism and Weak Field Einstein Equations?


Half life of radioactive elements: are there some atoms in a different state than others?


How would you visualise a curvature in spacetime?

Naive visualization of space-time curvature


Why doesn't a particle in uniform circular motion fall into the centre?


Is there an upper limit to temperature in thermodynamics or statistical mechanics


Need A Collection Textbooks To Use As Stepping Stones to QFT

A No-Nonsense Introduction to Quantum Field Theory


How to determine the position of a planet in our solar system?

How about an exact solution for the position of a planet as a function of time?


Generating power with a "straw" to space... Is it possible?

Would a pipe from the surface to the Earth's exosphere suck all atmosphere to the space?


Can water pressure ever be high enough to trap gas bubbles or keep them from surfacing?


Deriving the equation for Angular Momentum?

Definition respective derivation of angular momentum formula


How does thermal expansion actually happen on the quantum level?

What's the true reason behind thermal expansion?


What is the reason behind the equation $p = mv$?

Deriving $p = mv$ from translational symmetry (momentum conservation law)?


Is it possible to derive a non-mass gap from the Yang-Mills action?

Why is the Yang–Mills existence and mass gap problem so fundamental?


Translational Energy levels in Quantum Mechanics

Validity of naively computing the de Broglie wavelength of a macroscopic object


Is there any general theorem which specifies conditions where the critical solution of an action is unique (for given boundary conditions)?

When/why does the principle of least action plus boundary conditions not uniquely specify a path?


How can photon have wave properties if they travel at the speed of light?

Does a photon in vacuum have a rest frame?


Ball rotating in a circle without rope/string - why doesn't the ball fall after the peak?

What is the reason behind water not falling from a bucket at the top of loop?


Finding an object's final velocity with distance dependant force

Time taken for object in space to fall to earth


If photons travel at the speed of light how can they ever be destroyed?

How does a photon experience space and time?


About the use of Newtonian Relations for the movement of stars in the Galaxy


The expectation value of momentum in an infinite well stationary state

What's the deal with momentum in the infinite square well?


What is the cause of discrete or quantized energy levels in an atom?

Discreteness of set of energy eigenvalues


Predict decay chain of a radioactive element


Does the temperature of a body depend on the frame of reference?

Is temperature a Lorentz invariant in relativity?


Schwarzschild metric, acceleration of ball before it's dropped

What is the weight equation through general relativity?


Redshifting of Light and the expansion of the universe


Variables in the Dirac Equation Lagrangian

Can we treat $\psi^{c}$ as a field independent from $\psi$?


Why is the speed of light exactly $299,792.458$ m/s and not faster or slower?

The origin of the value of speed of light in vacuum


What is Electromotive force (EMF)? How is it related to potential difference?


How to distinguish first-order Feynman diagrams from the rest?

How to tell the order of a Feynman diagram?


Do double slit experiment with big balls

What would diffraction of a macroscopic object look like?


Energy of particle in General Relativity

How does $p\cdot u$ relate to observed energy and momentum for a massive particle?


How do Black Bodies Absorb and Emit Radiation?

What are the various physical mechanisms for energy transfer to the photon during blackbody emission?


Ordering of Indices in $\Lambda^\mu_{\space\space\nu}$

Index notation Lorentz transfromation matrix


Why disturbance in just electric and magnetic field is not enough to produce electromagnetic waves?

Why doesn't a charged particle moving with constant velocity produce electromagnetic waves?


What would the effects of the GW150914 gravity wave burst be on observers much closer that 1.3B LY?

How close would you have to be to the merger of two black holes, for the effects of gravitational waves to be detected without instruments?


Question about the trace in simplifying $e\!-\!e$ cross section

Why does the trace show up in such expressions?


Angular momentum of electrons in orbitals


Why will a dropped object land at the same time as a sideways thrown one?

2 balls falling hit the ground at the same time


Matter beyond the event horizon should time travel?

Will free-fall object into black hole exceed speed of light $c$ before hitting black hole surface?


How is it possible that momentum is conserved but kinetic energy is changed?

How can momentum but not energy be conserved in an inelastic collision?


Thermodynamic process with a decrease in entropy

Don't certain processes decrease entropy?


Self-study book for dynamical systems theory?


Does the speed of light vary in non-inertial frames?


Is there a reaction force for a reaction force?


Air oscillation at open window of a moving car

Why, when one opens 1 car window, does that noise occur?


Particle spin as evidence of space-time torsion

Spacetime Torsion, the Spin tensor, and intrinsic spin in Einstein-Cartan theory


Why do large angular displacements affect the amplitude of a simple pendulum?

Show bigger amplitude of physical pendulum means bigger period


Special Relativity - Why does time dilation cause length contraction?


Why does all the current flow through a short circuit if its voltage drop is considered zero?


Why arrow stays tangent to its trajectory?

Why do archery arrows tilt downwards in their descent?


Couder's walking droplets - what are issues of using its intuitions to interpret quantum analogoues?

Bell's theorem and fluid-mechanical experiments using droplets: are local hidden-variable theories possible after all?


Literature advice: Covariant formulation of classical physics

Classical mechanics without coordinates book


Saturated BJT Transistors. $V_{CE} < V_{BE}$ : AKA - Things that make you go "Hmmmm"

Saturated BJT Transistors. V CE < V BE : AKA - Things that make you go “Hmmmm”


Quantum Mechanical Hamiltonians without Classical Analogues

Quantum systems without a classical analogue?


Gravitational potential energy on the Earth's surface

Is gravitational potential energy proportional or inversely proportional to distance?


Does the mass of a particle increase with increasing velocity

Why does the (relativistic) mass of an object increase when its speed approaches that of light?


How many particles are there in the entire universe?

Dumbed-down explanation how scientists know the number of atoms in the universe?


Why does anyone take Cold Fusion seriously?


What's the earliest a planet could have been formed?


What is the general procedure for constructing the Penrose diagram for an arbitrary $(1+1)d$ spacetime?


Why do we use Root Mean Square (RMS) values when talking about AC voltage


With Permanent magnet or electrificated sticks to create EM waves

Does waving a magnet around create light?


Similarity in the formula of gravitational force and electrostatic force

Why are so many forces explainable using inverse squares when space is three dimensional?


Why are the planets rotating on their own axis?


How precise must the energies match for absorption of photons?


Rutherford experiment of alpha particles

How did Rutherford conclude that most of the mass (as well as the positive charge) was concentrated in the nucleus?


Explanation about Curl in electromagnetism

What is the physical significance of curl $\nabla\times\boldsymbol{V}$?


Symmetrical twin paradox in a closed universe


Calculating acceleration due to gravity using General Relativity

$N$-body simulation in General Relativity


Newtonian mechanics and calculus, looking for a good intro book to both together

Recommendations for good Newtonian mechanics and kinematics books


Should the moon eventually collide with the Earth if no force besides the earth's gravitation enacted upon it?

Why doesn't the Moon fall onto the Earth?


Why ordinary sources of light such as bulb, flash light,.. etc cannot behave as coherent sources?

Why is a filament lamp an incoherent light source?


How to quantize a system if kinetic energy depends on coordinate?

Quantization of a particle on a spherical surface


Do partial derivation respect to velocity and total derivation respect to time commute?

Total time derivatives and partial coordinate derivatives in classical mechanics


If a Spacecraft Was To Launch From An Asteroid Would it Be Easier To Minimize The Required Escape Velocity By Launching At A 45 degree angle?


Problem in finding the divergence at a point

Divergence of $\frac{ \hat {\bf r}}{r^2} \equiv \frac{{\bf r}}{r^3}$, what is the 'paradox'?


Is Weyl transformation part of diffeomorphism? Does a gravitational anomaly capture also the anomaly due to Weyl transformation?

Conformal transformation/ Weyl scaling are they two different things? Confused!


Can anyone recommend books to learn about black holes?


Is the harmonic oscillator potential unique in having equally spaced discrete energy levels?


Why does $\textbf{F}=- \boldsymbol{\nabla} V$?

Why is the potential energy equal to the negative integral of a force?


Does the earth has any electric field as the earth's magnetic field is changing over time?

Can the Earth's magnetic field be used to generate electricity?


What's the evolution of a state under an adiabatic evolution?

Evolution operator for time-dependent Hamiltonian


Proving that acceleration perpendicular to velocity only changes it's direction

Does an acceleration always perpendicular to velocity imply a circular motion?


Does the photon have a rest mass equal to $E/c^2$, where $E =$ photon energy?


Why physically do things in general tend to move toward a lower potential value in a potential field?

Why does a system try to minimize potential energy?


Why do we use Root Mean Square (RMS) values when talking about AC voltage


How dangerous is a neutrino experiment near human habitation?


Is it possible for information to be transmitted faster than light by using a rigid pole?


Adding angular momenta in quantum mechanics


Do we actually know the charges of quarks?

How has quark electric charge been directly measured?


How does gravity cause acceleration? Also what means spacetime?

Why would spacetime curvature cause gravity?


Why is it interesting to study gravity in (2+1)D?

What do we learn from gravity in three spacetime dimensions?


What is the magnetic field inside hollow ball of magnets?


Do we hear anything special when the beat frequency is in audible range, but the sounds producing the beats are not?

If two sound waves that are different frequencies create beats that occur several hundred times per second, can you hear this effect as its own tone?


If centrifugal force isn't real then why am I being pushed on a merry go rournd?


Why do harmonics occur when you pluck a string?


Can gravity give neutrons a longer lifespan?

What stabilizes neutrons against beta decay in a neutron star?


Does acceleration in free fall disprove Newtonian mechanics?

Why does a free-falling body experience no force despite accelerating?


Why is deuterium and tritium used in fusion reactions rather than two deuterium?


Why does a star with its core collapsing and about to undergo a supernova, explode, instead of rapidly collapsing all of its matter into a black hole?


Could Dark Energy just be particles with negative mass?


Why doesn't current flow in reverse biased diode?


Why can't $\psi' (x,t)$ be discontinuous?


Optical physics and principle of reversibility

Does light reflect if incident at exactly the critical angle?


Why is the center of mass the pivot of rotation?


Why does space expansion not expand matter?


Why can't we see whats inside black holes?


If I push or hit an object in space will it rotate or move along a straight line?


Coefficient of friction between 2 surfaces

Work out friction coefficient using the two material's properties


How the current of a wire pass so quickly if it has that less drift velocity of electrons.?


What makes light to be a special part of the electromagnetic spectrum that it has a particle?

Do x-rays and gamma rays also contain photons like visible light does?


Is Angular Momentum Defined Only For Spinning Objects?

How is Angular Momentum Conserved when Mass is Released?


Reason for strange "canyons" of dust on the cooling platform


Where does the extra $U(1)$ symmetry come from in spontaneous symmetry breaking?

Where does in GUT symmetry breaking $U(1)$ come from?


Is there a way to derive the field of arbitrarily moving charge from Maxwell's equations?

Deriving Heaviside-Feynman formula for the electric field of an arbitrarily moving charge from Lienard-Wiechert potential


Will an off-center force cause an object to rotate if there is no resistance?


What part of the cylinder displaces some volume from the second liquid (which is used for the buoyant force)?

Problem regarding Buoyancy forces and Archimedes principle


What is the difference between Kretschmann and Ricci scalar curvature?


Why doesn't electron collide with nucleus?

Why don't electrons crash into the nuclei they "orbit"?


Understanding transverse oscillation in 1 mass, 2 spring systems


Accidental degeneracy in Hydrogen Energies

Why are hydrogen energy levels degenerate in $\ell$ and $m$?


If Light is in part a Moving Magnetic Field. Why Doesn't it Generate Voltage When it Passes a Conductor?

Does light induce an electric current in a conductor?


Which of the following Delta/Pie to Star/T transformation is correct?

Why do the following Network Transformations give different answers?


Is diamagnetism a static or dynamic effect?


Where does the '2' Factor come from in the Coriolis Force?

The two causes for the factor 2 in Coriolis effect


Making a tunnel in the Earth through its center

If it was possible to dig a hole that went from one side of the Earth to the other...


Why is the rocket equation different from the product rule?

Second law of Newton for variable mass systems


Quarks in a hadron: where does the mass come from?


What's the origin of the flattened X that appears when of a small (but powerfull enough) light is reflected in our non-powered TV screen?


Could this be faster than the speed of light?

Is it possible for information to be transmitted faster than light by using a rigid pole?


Why is angular velocity a vector quantity?

How is it that angular velocities are vectors, while rotations aren't?


Why isn't Higgs coupling considered a fifth fundamental force?


Gravitational Force between two finite rigid bodies

What's the difference between centre of mass & centre of gravity for massive bodies?


A question about resistivity ( high school physics )

If Resistivity = $\frac{RA}{L}$, why does it not depend on dimension?


What happens to momentum when a car crashes into a barrier?

Is momentum conserved in this situation?


Is the center of the universe at absolute rest?


Partition function for two particles such as bosons fermions

Partition function of bosons vs fermions


Twin paradox - confusions in explanation

What is the proper way to explain the twin paradox?


Why Empty universe have to obey the Negative Curvature?

What is the curvature of an empty universe?


Why do many people say that virtual particles do not conserve energy?


Force on a test charge placed at the center of a 13-sided regular polygon?


Is the Higgs boson an elementary particle? If so, why does it decay?

Why are muons considered to be elementary particles in the Standard Model?


If is work done by magnetic field is 0 then why does 2 magnets attract when kept together?

How can magnets be used to pick up pieces of metal when the force from a magnetic field does no work?


What is an observer in quantum mechanics?


What is the difference between Wien's Displacement Law for peak frequency vs peak wavelength?

The strange thing about the maximum in Planck's law


Time dilation under different references paradox


Kinetic energy of disk rotating around axis parallel to the one through its center

Kinetic energy of an object rotating about an axis not through the center of mass


Are vacuum fluctuations really happening all the time?


Phase shift of 180 degrees of transversal wave on reflection from denser medium


What is the "rate" of the "passage of time"? How does a physicist define and measure time?

What is time, does it flow, and if so what defines its direction?


Digging a hole in the moon across its diameter

If it was possible to dig a hole that went from one side of the Earth to the other...


Is everything relative? Length and time?

If everything in the universe doubled in size overnight, would it be noticeable?


Is there any change in temperature due to special relativity?

Is temperature a Lorentz invariant in relativity?


Unpolarized light - Why don't light sources then look invisible?

How come unpolarized light does not undergo destructive interference?


How does a temperature change affect the pitch of the fundamental frequency produced by vibrating string?

How does temperature affect the frequency produced by a fixed vibrating string


Is image seen in optical bench experiment using two pin and convex lens real or virtual?


Can length contraction help the moving observer reach a star system 'faster'?

Can I measure a journey time < 100 years on a 100 light year voyage?


How does this "simple" electric train work?


Which books/videos do you recommend for astrophysics?

What are good books for graduates/undergraduates in Astrophysics?


Symmetrical twin paradox in a closed universe


Maxwell Lagrangian where $F$ and its derivatives are the variables (i.e., without replacing $F={\rm d}A$)

Is there either a Lagrangian or a Hamiltonian formulation of electromagnetism with continuous distributions of magnetic monopoles?


How did we come up with the formula of the work done by a force?

Work and Kinetic energy rely on each other which came first?


Is momentum conserved in the collision of a ball with a hanging rod?


How are two unequal applied forces at the end of a massless string result in a constant tension throughout?

If A and B are two persons at the end of an ideal rope, where A is applying a force of 70N and B is applying force of 60N then what is the force on A?


Is the spring constant $k$ changed when you divide a spring into parts?


Difference between escape velocity and speed

Is escape velocity really a velocity (rather than a speed)?


Why does the wavelength gets shorter in the denser medium in refraction?

Why does wavelength change as light enters a different medium?


Is uncertainty principle due to entropy?

Is quantum uncertainty principle related to thermodynamics?


Why was helium hydride ion HeH$^+$, not hydrogen H$_2$, the first molecule formed in the early universe?

Was helium hydride really the first molecule?


Book recommendation for nonequilibrium thermo/stat mech

Modern textbook on statistical field theory with an emphasis on applications to non-equilibrium phenomena?


3D donuts and the centre of a black hole


Does humidity make cold air feel colder?


Why does it feel warmer when it is snowing?


What does it mean for two objects to "touch"?


Why can a free particle not exists in a stationary state?

Normalisation of free particle wavefunction


Does the kinetic friction change when the angle of inclination is changed on a mass sliding down and inclined plane

Why does the co-efficent of kinetic friction of a block on an inclined plane not change when you increase the angle of the plane?


How does the strength of magnetic field at the center of current carrying circular coil depends on the radius, number of turns and current


Were more stellar objects part of our observable universe in the past?

As the universe ages, will we see more stars or less?


If Hubble parameter varies with time how much it differs for low distances (present) and deep space (past)?

How does the Hubble parameter change with the age of the universe?


Why do the planets' orbital distances fall on an exponential curve?


How do you calculate the acceleration due to gravity of a massive object (black hole)

What is the weight equation through general relativity?


Kepler problem in time: how do two gravitationally attracted particles move?


What is $\Delta t$ in the time-energy uncertainty principle?


if Higgs boson stopped existing, what would happen?

What happens to matter in a standard model with zero Higgs VEV?


At what point in size does gravity force a celestial body to become "round"?

What's the biggest cube you could have before gravity rounded it?


Why do wheels appear to revolve opposite to the direction they are rotating?


Why is desaturated orange = brown, but desaturated blue is just plain blue?

Are colors grounded in physics or are they a matter of human perception?


Why does a bubble take a spherical shape?


Hexadecapole potential using point particles?


What is a good introductory book on quantum mechanics?


For an intrinsic semiconductor, why is fermi level half-way?

What does Fermi level in the band gap mean?


Where does this formula for normal ordering in QFT come from?

Time-ordering vs normal-ordering and the two-point function/propagator


Can you explain this "Theory of Everything"?


Can the Lorentz force expression be derived from Maxwell's equations?


Why $c$ is $3\times10^8$ times faster than a $1\ \mathrm{m/s}$ car?

The origin of the value of speed of light in vacuum


What conservation law corresponds to Lorentz boosts?


How can we derive the schrodinger wave equation?

Is the Schrödinger equation derived or postulated?


How can a point hold mass or charge where it doesn't tell anything except position?

How can a point-particle have properties?


Is there any quantum experiments or effects that you can do at home?


Will my coffee end up colder if I wait to put in the milk?

Does tea stay hotter with the milk in it?


Is this a correct description of Hawking Radiation?


If energy can't be created and can't destroyed

Conservation law of energy and Big Bang?


Does quantum mechanics have any insight into why and how photons get adsorbed into atoms?

Do we really not know why atoms 'decide' to produce a photon?


Motion of a ball in a tunnel along Earth's diameter

If it was possible to dig a hole that went from one side of the Earth to the other...


How is Schwinger's quantum action principle related to least action?

Is the quantum action principle of Schwinger a variational principle?


If 99% of an atom empty, and our body is made of atoms, does that mean 99% of our body is empty?

Why doesn't matter pass through other matter if atoms are 99.999% empty space?


Is a planets orbit really a straight line through curved spacetime?

Why do we still need to think of gravity as a force?


Perpetual motion machine with permanent magnets


What is a good book to learn AP Physics C?

Recommendations for good Newtonian mechanics and kinematics books


Define Pressure at A point. Why is it a Scalar?


Is the Big Bang notion compatible with the flat space? (A problem with the **moment** of Big Bang, not with the place of it)


Difference between anti-matter and matter black holes


How do we know that Dark Energy has homogeneous energy density?

Is the energy density of vacuum uniform in the whole universe?


Why the eigenvalues of orbital angular momentum $L$ never take half-integral values?

Half-integer eigenvalues of orbital angular momentum


Does the Planck scale imply that spacetime is discrete?


What is the most general conception/formalization of "energy"?

What's the real fundamental definition of energy?


Supersymmetric Localization (Mirror Symmetry)


I was wondering if the mass of an object can be measured by the effect it has on a body of water if it was dropped from a certain height?


What if interactions such as gravity faded with respect to the cube of distance, rather than square?


Another layman blackhole question, pulling one end of a string out from behind the event horizon


Does a wave blue-shifted by the doppler effect increase in energy?

Conservation of energy and Doppler effect?


What is the result that that differs by many orders of magnitude between QM and GR?

A list of inconveniences between quantum mechanics and (general) relativity?


why path of an electron in an orbit is uncertain?


Is there a direct physical interpretation for the complex wavefunction?


Should stellar black holes contain a singularity? (in GR)


Normal ordering of operators: Commutator or no commutator

Normal ordering of the commutator between annihilation and creation operator


How can the Neutral wire be 0V if its AC?

Difference between live and neutral wires


What proof do we have that dark matter is matter?

Is Dark Matter called "Matter" only because of gravity?


According to special relativity, has the future already happened?


Difference between an entangled pair of photon and two magnets in a box?

Why is quantum entanglement considered to be an active link between particles?


Step in the derivation of complex wave notation

What is the physical significance of the imaginary part when plane waves are represented as $e^{i(kx-\omega t)}$?


Accelerometer outputs vs the real accelerations

Ficticious forces influences what an accelerometer exactly measures?


Why does kirchoffs voltage law hold in AC circuits?


On causality in physics: is the concept of cause an operational concept in physics?

Is causality a formalised concept in physics?


Why doesn't the wave's frequency change as it gets refracted?

Why does the frequency of a wave remain constant?


What is meant by globally hyperbolic spacetime?

Intuitive meaning of Globally Hyperbolic


'My question is about' ...the size of the Universe after Inflation


Mathematical software for calculating Christoffel symbols, curvature, etc

Open source computer algebra systems for general relativity


How can I calculate the final velocities of two spheres after an elastic collision?

Calculating new velocities of $n$-dimensional particles after collision


According to Einstein & Brian Greene, does the photon remain stationary in the fourth dimension?

Does a photon in vacuum have a rest frame?


Why is the definition of inertial mass circular?

Are Newton's "laws" of motion laws or definitions of force and mass?


Why every system tends to be more stable?

Why does a system try to minimize potential energy?


How to prove that the Einstein velocity addition is a one-parameter composition formula of a one parameter group?

How to derive addition of velocities without the Lorentz transformation?


Time it would take for sound to travel between moon and earth?


Why is window glass only transparent from one directional axis?


What is the difference between a tensor, vector, and a matrix?

What is the difference between a spinor and a vector or a tensor?


What causes a charged particle to follow circular motion in a magnetic field?

Is there an intuitive explanation for why Lorentz force is perpendicular to a particle's velocity and the magnetic field?


Why doesn't current pass through a resistance if there is another path without resistance?


Why is current the same everywhere in a circuit? (DC)

How does the current remain the same in a circuit?


Is the decay of nuclei also depending on the 'age' of nuclei or whether they are created or not?

Is there any thing other than time that "triggers" a radioactive atom to decay?


Newton's Cradle: why does it stay symmetric?


Why don't we have just one type of charge? Why do we need two?

Can a third type of electrical charge exist?


Partial Differentiation without chain rule in Euler Lagrange Equations

Calculus of variations -- how does it make sense to vary the position and the velocity independently?


How is the Earth moving in a elliptical orbit around the Sun?


Normal force in a compound pendulum (physical pundulum) system?


Capacitor connected across two isolated sources

Capacitor with different charges on each plate


Why are neutrinos more weakly interacting than light?


What is the difference between weight and mass?


Could negative dimension ever make sense?


Reference frame and conservation of energy

Where does the extra kinetic energy of the rocket come from?


What is the average temperature of mass in the universe?

What's the avarage temperature of the Universe?


Why are we allowed to decompose a function of two variables $f(x,y)$ into the form $\sum_n^\infty c_n(y)\psi_n(x)$?

Expanding two-variable function $f(x,y)$ over the complete sets $\{ g_{i}(x) \}$ and $\{ h_{j}(y) \}$


Correct Definition of Angular Momentum of a Charged Particle in an Electromagnetic Field? (Classical Mechanics)


If the Universe is expanding, then why will Andromeda collide with the Milky Way?

If the Universe is expanding, how is that galaxies run into each other?


In Newtonian pressure, what type of function is force?


Would time reverse if we were to go faster than the speed of light?

How does faster than light travel violate causality?


Does time expand with space? (or contract)


Finding pressure differences considering variations in different parameters


What is the shape of a rain water drop and how it forms?

Are raindrops actually "shaped like tears" when they fall?


Is 220 V, 50 A equally dangerous for a person as 1A, 11000 V?

What causes an electric shock - Current or Voltage?


Is the reason we haven't fully combined GR and QM purely mathematical (rather than conceptual or empirical)?

A list of inconveniences between quantum mechanics and (general) relativity?


Why do we need the second postulate in special relativity?

Einstein's first postulate implies the second?


Spacelike interval and length contraction


Conservation of momentum for ball rolling up hill


What does a non-integrable Hamiltonian system mean?


Why don't electrons crash into the nuclei they "orbit"?


Magnetic field created by the electron spin

What does the magnetic field of the (quantum-mechanical) electron look like?


How everything will act in a universe of two time dimensions?

Intuition for multiple temporal dimensions


Is time travel possible? Is it possible to go back in time?


Why is everything floating in space so cold?


Why is the voltage drop across an ideal wire zero?


We can not do work with internal force is it right?


Temperature of room for open door of refrigerator


Is it possible to prove that an elephant and a human could jump to the same height?

What's wrong with Arnold's scaling argument on jumping height?


If I run along the aisle of a bus traveling at (almost) the speed of light, can I travel faster than the speed of light?


How have protons and neutrons been scientifically eliminated as candidates for Dark Matter?

Why isn't dark matter just ordinary matter?


A rubber ball hits a stationary door and bounces back, while a another ball sticks. Why doesn't the rubber ball violate conservation of energy?


Where did the energy for the big bang come from?

Is the total energy of the universe zero?


What is a suitable book to learn general relativity for high school students?

What are the prerequisites to studying general relativity?


Does the shiny side of foil keep food warm?

Does more reflective aluminum foil make a room cooler compared to less reflective foil?


What does that mean, a black hole "rotates"?

How can a singularity in a black hole rotate if it's just a point?


Is there anywhere online where I could simulate the schrodinger equation with different Hamiltonian's?

Computer simulation of Schrödinger equation


Why does the single slit in Young's Double slit experiment need to be narrow?

Why must the single slit in a double slit experiment be narrow?


Does maintaining a lower indoor temperature cost the same heating energy as maintaining a higher indoor temperature

Does it require more energy to maintain higher temperature in the same environment?


Would it help if you jump inside a free falling elevator?


What is a Field? Do all things have them? What types of fields are there?


Maximum Possible Deceleration when braking


How can photons have frequency without vibration?


Why are springs shaped the way they are?


Why can't we calculate the absolute velocity of the Earth using the speed of light?

If I am travelling on a car at around 60 km/h, and I shine a light, does that mean that the light is travelling faster than the speed of light?


Why do they specify the differential of Work using an lowercase delta $\delta W$, instead of $dW$


How can anything ever fall into a black hole as seen from an outside observer?


Is there any evidence of black holes existing?


Can I destroy a star faster by trapping it in a spherical mirror?

What would happen to a star if a Dyson sphere lined with mirrors reflected a significant portion of the stars light back to the star


Is the speed of light constant even for an object which is accelerating?


How can classical electrodynamics be a complete theory of electromagnetism when it's based only on special relativity?


Electron flow and electric field question

Why is the charge naming convention wrong?


Can an object achieve speed greater than speed of light?

Accelerating particles to speeds infinitesimally close to the speed of light?


What happens to the energy when two waves completely interfere destructively?

What happens to the energy when waves perfectly cancel each other?


For which object is time dilation, actually (absolutely) happening?


How can gravity be independent from velocity?

If a mass moves close to the speed of light, does it turn into a black hole?


In longitudional clock, for the return half tick why is the time in stationary frame less than the time in moving frame?

What if a light clock travels perpendicular to mirrors that make up the clock?


How to sail downwind faster than the wind?


Areas of physics and physical scenarios where jerk comes up

Is there any case in physics where the equations of motion depend on high time derivatives of the position?


What is the difference between $U(r)=mgr$ and $U(r)=-G\frac{M_{1}M_{2}}{r}$?

Near Earth vs Newtonian gravitational potential


Is this an eigenfunction of a ladder operator?

Is there a simple way of finding the eigenstates of the creation and annihilation operator in QM?


Does the Biot Savart law only hold for magnetostatics?

Is Biot-Savart Law valid for time-varying currents unlike Ampere's law?


Adding many more neutrons to a nucleus decreases stability?


Sign convention of force due to universal law of gravitation

How do I get the negative sign in the expression for Gravitational Potential Energy?


Why do the operators on either side of Schrodinger's equation show different hermitivity?

An operator on the other side of the Schrödinger equation


Eigenvectors and Eigenvalues of $a^\dagger a$

Proof that the One-Dimensional Simple Harmonic Oscillator is Non-Degenerate?


Where does the energy for osmosis come from?


Torque Equation for a point other than the axis of rotation


How to understand $L_4$ and $L_5$ Lagrange points gravity balance?

Why are $L_4$ and $L_5$ lagrangian points stable?


Why are the Planck charge and Planck mass values so much larger than observed particles?

Planck mass is about the mass of one eyebrow hair


Supposed we proved that we lived in a simulation. What are some of the current clues we would use to help us acknowledge this?


Why does the atmosphere rotate along with the earth?


How does the lift force of an airplane work?


What is the proof that the speed of light in vacuum is independent of relative motion?

Theoretical proof of the constant of speed of light $c$ in vacuum in all frames of references


Gravity of black hole and that of star that formed it

When a star becomes a black hole, does its gravitational field become stronger?


Acceleration of an object dropped inside an accelerating elevator


How can we determine time flows in one direction?

What is time, does it flow, and if so what defines its direction?


An explanation for the Landauer's principle


Is the relation between Hamilton's and Lagrange's equations the same as that between conservation of energy and the equations of motion?

Equivalence between Hamiltonian and Lagrangian Mechanics


Dark matter and standard model of cosmology: how does it enter into the equation?

How the CMB anisotropy is linked to the existence of cold dark matter and dark energy?


Adding uncertainties when you cannot make any assumptions about the measurements


Was the big bang a black hole that collapsed

Has the universe we live in started as a black hole that is imploding?


What motivates the definition of the Klein-Gordon Inner Product?


Unpolarized EM wave: is there no electric/magnetic field?

Electromagnetic field of unpolarized light


What does temperature refer to in the vacuum of space?


Do gravitational waves lose energy through interaction with i.e. matter or magnetic fields?

Where does gravitational waves' energy go?


What is the physical significance of a Lagrangian and an action in particle physics?


Why Optical Microscope can not be used for higher magnification

Optical microscope magnification limits?


Why do heavier objects roll faster down a hill?

Why do heavier objects fall faster on hills but not in straight drops?


If we know spin isn't actually rotation, why do we still speak of intrinsic angular momentum?

Why can't I just think the spin as rotating?


If it was possible to dig a hole that went from one side of the Earth to the other...


The relationship between mass and incline on an object's speed

If mass is added to a toy car does it affect its speed making it faster


If "time is relative", what does "the universe is 13 billion years old" mean?

Does the universe have a different age to different observers?


Quantum Field Theory Interpretation of $\hat{\phi}|0\rangle$

Getting particles from fields: normalization issue or localization issue?


Crash course in classical thermodynamics


Copenhagen interpretation and argument of boundary condition


How does my lab's Helium-filled cathode ray tube produce a blue-ish glow?

Which cyan colored line is produced in the Thomson e/m apparatus?


How is group theory related to particle physics?

What is the significance of Lie groups $SO(3)$ and $SU(2)$ to particle physics?


How does mass of the exchange particles affect the range of a force?

What is the relation between interaction range and the mass of gauge bosons?


example from physics where the action of the physical trajectory has a saddlepoint?

Confusion regarding the principle of least action in Landau & Lifshitz "The Classical Theory of Fields"


Alternative to the explanation of large scales phenomena

Theory that gets rid of dark matter/energy


Given Newton's third law, why are things capable of moving?


Is it possible for information to be transmitted faster than light by using a rigid pole?


Scepticism regarding the exponent of -2 in Coulombs law?

Does Coulomb's Law, with Gauss's Law, imply the existence of only three spatial dimensions?


If gravity arises from the curvature of spacetime, why is there a need for gravitons?

What are the reasons to expect that gravity should be quantized?


Work, energy and power of massive spring


What is the fastest speed you can ride a bicycle on wet roads without getting wet?

What is the angle at which water is splashed when a vehicle tyre rides in water on the road?


Finding the correct units for the energy-momentum tensor?


Why does the electric field strength for a dipole go as $1/r^3$?

Why does the field of an electric dipole drop off as $1/r^3$?


How do Black-Hole singularity and Heisenberg uncertainty principal can co-exist?

Do black holes violate the uncertainty principle?


How do I use the Lagrangian to determine an orbital path?

What are common methods for calculating the time dependency of elliptical orbit?


Is the acceleration due to gravity the same no matter the mass of the object?

Don't heavier objects actually fall faster because they exert their own gravity?


Is this definition of "escape velocity" correct?

Another layman blackhole question, pulling one end of a string out from behind the event horizon


Why is light described by a null geodesic?


What do we mean by the size of the universe?

How do we know the size of the universe?


Nothing can travel faster than the speed of the light, but could this be an exception?

Is it possible for information to be transmitted faster than light by using a rigid pole?


How are the higher derivatives (jerk, jounce) of position with respect to time used in physics?

Why don't we consider jerk in physics classes?


Are moving objects producing stronger gravity fields?

If a mass moves close to the speed of light, does it turn into a black hole?


Can a baryon consist of two quarks and an antiquark? Or a pentaquark be made of three quarks and two antiquarks?

Why do quarks tend to bond in groups of three?


The magnitude of the normal force on an inclined plane in two different coordinate systems

Question about normal force acting on a mass on an inclined plane


Why doesn't finite field propagation speed contradict Gauss's law?

How would Gauss' law hold in time varying electric fields?


Why is refraction of light at a boundary wavelength dependent, and are the two proportional?

Why do prisms work (why is refraction frequency dependent)?


Viewing computer screen through 3D glasses, why the asymmetry?


Can a particle have a speed exceeding that of a photon in vacuum?


How can a shadow move faster than light?

Can a shadow move faster than the speed of light?


Finding the wave function of a quantum harmonic oscillator

Can we measure "wavefunction" of quantum particles?


Can a metric in General Relativity, Supergravity, String Theory, etc., be asymmetric?


Difference between $\Delta$, $d$ and $\delta$


Can a light be bent by a magnetic field?


Why are axions considered cold dark matter?

If neutrinos are disfavoured as DM candidates why aren't axions?


Compared to the rest in Baryon Octet, why is neutron decay lifetime so long?

Why is the (free) neutron lifetime so long?


Newton's first law of motion a corollary of second law?


Is the wave-particle duality a real duality?


Why you need a graviton when you have the higgs boson?


Can an object move faster than the speed of light in a medium?

What happens if light/particles exceeded the speed of light for a particular medium?


Are matter waves (de Broglie) classified as transverse or longitudinal?


How is quantization related to commutation?

Why does non-commutativity in quantum mechanics require us to use Hilbert spaces?


Is this a possible monopole setup, or will it cancel out?


Primordial galaxies and associated mass of blackholes

Is there a limit as to how fast a black hole can grow?


What is the simplest way to prove that Earth orbits the Sun?


Why does reflection occur on transparent materials?

Why does a window become a mirror at night?


Relationship between physical and information entropy

Is information entropy the same as thermodynamic entropy?


Torque on dipole in a non-uniform electric field

Torque on electric dipole placed in non uniform electric field


If the Earth would change into a ball of water, how wil its form develop, considering only the Sun's and Moon's influence?

What happens to the water on the surface of the Earth if the Earth is not rotating about its axis in the Earth-Moon system?


Why is it that a stationary bike will fall but a moving one won't?

Why doesn't a bike/bicycle fall if going with a high speed?


Force is generally a function of $\mathbf{x}$, $\mathbf{v}$ (or $\mathbf{p}$) and $t$

What is function of force $F$ and work $W$?


Are rainbows three dimensional? If so, what determines their depth?


is there any force on a tennis ball that is being thrown in the forward direction after it leaves the persons hand?

Why is it that a force is not required for a body to move at constant velocity?


Is this news article about quantum radar legit?

Quantum entanglement as practical method of superluminal communication


When a charge starts moving, does it's electric field change into magnetic field?

How do moving charges produce magnetic fields?


How is a Kibble balance used in the new definition of the kilogram, and what's the connection between the balance and Planck's constant?

What are the proposed realizations in the New SI for the kilogram, ampere, kelvin and mole?


Why Gauss divergence theorem isn't working?

Divergence of Electric Field Due to a Point Charge


Was the singularity just a mini model of our current unvierse?


A possibility of the theoretical derivation of Pauli's Exclusion Principle

Theoretical Proof of Pauli's Exclusion Principle


What is the upper limit for the size of an atom?


Is time passing really differs on other planets/in interstellar?

Relativistic time dilation on Mars compared to Earth?


Can someone give me a clear explanation on this topic?

Intuitive analysis of gradient, divergence, curl


If electric fields add, and intensity is proportional to $E^2$, doesn't superposing light violate energy conservation?

How to explain the relationship between wave's amplitude and intensity?


Why does the humidifier "really" make a stove's flame orange?

Why does the humidifier make a stove's flame orange?


How does Light have momentum without mass?

If photons have no mass, how can they have momentum?


Is $E^2=(mc^2)^2+(pc)^2$ correct, or is $E=mc^2$ the correct one?


Doesn't the fact that elementary particles are not black holes prove they are not point structures?

what is the difference between a blackhole and a point particle


Are all Bell tests valid only for linearly-polarized photons?

Is a single photon always circularly polarized?


Why do we use the $\left(\tfrac{1}{2}, \tfrac{1}{2}\right)$ rep for spin $1$ particles and not $(0, 1)$?

Can Poincare representations be embedded in non-standard Lorentz representations?


Friction and Work in Inertial Reference Frames

Work done changes between reference frames?


Are velocity and acceleration smooth quantities?


Speed of at expansion at the start of the big bang


What is wrong with my Cloud Chamber? I can't see supersaturated vapor or particles

What is wrong with my setup of cloud chamber?


Why do electrons revolve around the nucleus?

Why don't electrons crash into the nuclei they "orbit"?


Is the notion of 'weight of Earth' meaningless?


Uncertainty Principle for a Particle on a Ring

How can I solve this quantum mechanical "paradox"?


What are direct experimental evidences that quarks exist?

What evidence is there of the existence of quarks?


What is a good introductory text on statistical mechanics for math-student

Recommendations for statistical mechanics book


When a proton attracts an electron in the electromagnetic field is the proton "bending" the field?

Can all fundamental forces be fictitious forces?


How does the electric field inside a conductor become zero?


Maximum distance of a body in projectile motion from origin

Projectile motion maximum distance to origin


Why does decreasing the wavelength of light while maintaining intensity decrease current in photo electric effect

Photoelectric Effect - Dependence of current on frequency


How does the speed of electrons change around a circuit?


A question about Lorentz invariant argument when writing down the Dirac equation


What is the physical meaning of the connection and the curvature tensor?


Are photon energies universally quantized?


Direction of cross product of two vectors

Cross products/avoiding using your hand for the right hand rule in E and M


How do many conservative forces come together to make a non-conservative one?


Single photon interference, state "top" current theory

Double Slit experiment with just one photon or electron


How is the spin of the odd-odd nucleus 6Li explained?

Shell model of an odd-odd nucleus: $^6$Li


Does a black hole singularity compress mass back into energy?

Where does matter go after reaching singularity in uncharged black holes?


The existence of Delta baryons was experimentally proven?

Similar masses and lifetimes of the $\Delta$ baryons


How can two zero-dimensional black hole singularities have different masses?

Is a black hole singularity a single point?


infinitesimal areas and large areas scalar or vector quantities?


What it means that there is only one electron in universe?


Why does a prism refract light into a rainbow?

Why do prisms work (why is refraction frequency dependent)?


Why are photoelectrons emitted in the direction of incident photons?


Why is the spectrum of a star pretty much continuous?

Why is spectrum obtained by sunlight, said to be continuous?


Coulomb's law and the continuous charge model in an infinite charged plane


How EM waves are produced by accelerating charged particles?


Please help me with this doubt from thermodynamics


Is there really no transverse sound wave in air?

Do particles in a sound wave ever move transversally?


Why does rubbing feet against sheets create a spark?


How does water evaporate if it doesn't boil?


Why is a rainbow in the sky always an arch?


If gravitons are particles, how do they escape BH gravity if nothing can?


What is a good introductory book on quantum mechanics?


Definitions of relativistic kinetic energy and momentum

How can one motivate the relativistic momentum?


Why is the nucleus of an Iron atom so stable?


Symmetry arguments and plane sheet of charge

Scale invariance symmetry as a simple argument in an electrostatics problem


The Time That 2 Masses Will Collide Due To Newtonian Gravity


Why is there a controversy on whether mass increases with speed?


Why doesn't the gravitational force have a permittivity in its formula?

Why is there no permittivity-type constant for gravitation?


Observationally distinguishing a galaxy of antimatter from a galaxy of matter

Experimental observation of matter/antimatter in the universe


Quantum entanglement and affecting the particles

Quantum Entanglement - What's the big deal?


Can we define tension in a string as the reactive force produced in a string being pulled at both ends?


Discrepancy of $4π/c$ for radiated intensity in a blackbody radiation


How can photons destructively interfere?

What happens to the energy when waves perfectly cancel each other?


A question from "The meaning of the relativity, by A.Einstein" - Lorentz transformations

Interval preserving transformations are linear in special relativity


Is an extended spring gain mass from potential energy?

Does contracted spring weigh more than stretched one?


Is there one or more field of physics where $T$-symmetry is broken?


Why do meteors have different impact velocities?

Why is meteor speed what it appears to be?


Does the size of a photon change depending on the energy level/wavelength of the light?


How to treat differentials and infinitesimals?


How is energy transferred among particles of a body when we give some kinetic energy to it?


Energy propagation through stationary points of a standing wave

How does the energy in a standing wave travel beyond a node?


Does space itself fall into a black hole?

Can gravity be interpreted as the acceleration of spacetime towards an object?


What's the eccentricity of our sun's orbit around the center of the galaxy?

How can one get the eccentricity of the orbit of the Sun around center of the Milky Way?


Action reaction forces in an accelerating elevator

What identifies an action-reaction pair of forces?


What will be the expression between conformal time and scale factor for $\Lambda$ CDM model (for $k=0$, $\Omega_M + \Omega_\Lambda = 1$)?

Solution of Friedmann equation in terms of conformal time


Why the speed of light is independent of the relative motion of observer?

Why and how is the speed of light in vacuum constant, i.e., independent of reference frame?


Why mass has no effect on free-fall acceleration?

Why do two bodies of different masses fall at the same rate (in the absence of air resistance)?


Is there a gravitational force among antiparticles?

Has the gravitational interaction of antimatter ever been examined experimentally?


What is the physical significance of dot & cross product of vectors? Why is division not defined for vectors?


Why do water drops form spheres in space?

Why do floating water drops form spheres?


How does an isolated body in deep space 'know' it's rotating?

How does a spinning object "know" that it is spinning?


Different statements of the Heisenberg's uncertainty principle

Factor 2 in Heisenberg Uncertainty Principle: Which formula is correct?


Internal energy of ideal gas undergoing reversible adiabatic changes


Why is information indestructible in quantum mechanics?


Theoretical explanation behind alpha particle emission

Why are alpha particles such a prominent form of radiation and not other types of nucleon arrangement?


What is the unit vector in electric field formula?

Find the Unit Vector of a Three Dimensional Vector


Does the gravitational field possess an inertial mass?


Is there no law which includes an addition of different types quantities?

When can two quantities be added together?


Just clearing doubts about the obviousness of newton's laws

Why does Newton's Third Law actually work?


How does the formation of a solar system not break the second law of thermodynamics?


Kraus operator representation of reduced density matrix evolution question

Trouble with operator-sum representation of a quantum operation


How does an electron know whether a photon is of correct energy states?

How do photons know they can or can't excite electrons in atoms?


Slinky base does not immediately fall due to gravity


Length of tube used in barometer is less than 76cm

Size of mercury barometer and effect on its reading


Why the photon doesn't acquire mass with the Higgs mechanism?

Why don’t photons interact with the Higgs field?


Why do quantum effects of particles dominate when the thermal de Broglie wavelength becomes comparable to the inter-particle spacing?

Why do quantum effects dominates when the thermal de Broglie wavelength is on the order of or larger than the interparticle distance?


How do we know that any two points of an ideal wire must be equipotential?

Why is the voltage drop across an ideal wire zero?


Why is the singularity of the Big Bang not considered to be the center of the Universe?


What should I read to understand the math behind waves?

What's a good textbook to learn about waves and oscillations?


Change in Kinetic Energy in two different reference frames (one of them non-inertial)

Kinetic energy with respect to different reference frames


One force applied to one point of a rigid body: centre of mass and torque


Measuring quantum entanglement in paper by Ma et al

Delayed choice entanglement swapping: why are Alice & Bob's measurements useless without Victor's?


Gravitational Time Dilation Near Center of Gravity

Gravitational time dilation at the earth's center


Why can I feel the air inside the pump pressing against my finger when it is at 1 bar (atmospheric pressure)?


If we go to space why isn't the temperature high?


What is the physical meaning of $\epsilon_0$?


Is the universe fundamentally deterministic?


Would we see the past if we look to a mirror 1 light year away?


Which of the Physics textbooks would you recommend I read this quarter (Analytical Mechanics)?

Which Mechanics book is the best for beginner in math major?


Single particle passing through the double slit at a time


Why is there a difference between additive and subtractive trichromatic color theories?


What logical/mathematical proof do we have to show that, everything which is called electron are identically the same?


Quantum mechanics what do they mean by observing?

What is an observer in quantum mechanics?


What kind of forces would follow only the second part of shell theorem?


Books or papers recommendation on orbifold and CFT

Reading list and book recommendation on Conformal Field Theory


Solution for quadratic formula in physics problems

What do negative times and negative displacements represent in parametric projectile equations?


Do objects rotate around the torque vector or its center?


Suggest good books on Statistical mechanics

Recommendations for statistical mechanics book


Can gravity be shielded, like electromagnetism?


Are there other less famous yet accepted formalisms of Classical Mechanics?

Beyond Hamiltonian and Lagrangian mechanics


Why does the sky look blue rather than violet?


Shouldn't it be impossible to fall into a black hole?

Does someone falling into a black hole see the end of the universe?


Can we keep a photon bouncing of mirrors for a long time (eg days)?


Why is Methane a more effective greenhouse gas compared to Carbon dioxide?

Why is methane considered an important greenhouse gas?


What does the Canonical Commutation Relation (CCR) tell me about the overlap between Position and Momentum bases?


What force counteracts the electrostatic attraction of an electron in an atom?

Why don't electrons crash into the nuclei they "orbit"?


When is stress-energy tensor defined as variation of action with respect to metric conserved?


Why Pauli matrices are the same in any frame?

Lorentz transformation of Gamma matrices $\gamma^{\mu}$


How do physicists know when it is appropriate to use $\mathrm dx$ as if it is a number?

How to treat differentials and infinitesimals?


Why is length contracted but time is dilated?

Does SR treat time and space symmetrically? Then why does $t$ dilate while $\ell$ contracts?


Why Maxwell Distribution of Velocities curve is Bell Shaped? Is there any intuitive and/or quantum mechanical reason behind it?

Intuitive explanation of the shape of the Maxwell-Boltzmann distribution


Does a (charged) black hole evaporate its charge?

Evaporation of large charged black holes


A doubt in the concept of potential energy

Potential energy and the work energy theorem


On ways of describing the shape of strings fixed at 2 points

Shape of a string/chain/cable/rope/wire?


Is there a formula that gives the position of an object depending on the time, but which doesn't allow the object to surpass the speed of light?


What causes an electric shock - Current or Voltage?


Why do forces have to be mediated by bosons? (Or do they?)


Why is the tension force equal to the applied force when someone is lifting themself with a pulley?

Stretch length of horizontal and vertical springs


Coefficient of friction greater than one

Is the coefficient of friction always less than unity?


What is the status of existing measurements of the speed of gravity?


How do gravitational waves carry energy/radiation?


Why are "magnetic field lines" called "lines of force" when they are perpendicular to the direction of force?

Magnetic field lines vs. Electric field lines


When AC electricity is generated, how does the current flow?

What is the physical explanation for energy transport in simple electrical circuits?


Why do we weigh less on equator when centrifugal force isn't a force at all?

Why is Earth's gravity stronger at the poles?


Deriving $PV^n = \text{constant}$ for polytropic processes?

Derivation of polytropic process equation


Does teleportation through a stable traversable wormhole break any known laws of physics?

Are wormholes really a valid shortcut to distant points in the universe?


Why do charges not lose potential as they travel through the circuit before reaching a resistor?


Does it ever make sense to write the Cosmological Constant as: $\Lambda_{\mu\nu}$?

Why is the cosmological constant a scalar?


Does gravity slow the speed that light travels?


Does time expand with space? (or contract)


How does going faster than light cause going backward in time?

How does faster than light travel violate causality?


What if two twins flew off in opposite directions and were reunited in a perfectly symmetric way, would they have aged same?

What is the proper way to explain the twin paradox?


If black hole sucks in all masses, why does it suck in light if it is a form of energy (energy does not have mass)?


In physics sometimes we find energy that is negative. What does the negative sign indicate?


Permanent magnet's magnetic field arises due to the magnetic dipole moment of the electrons inside the magnet?


How is Einstein's postulate about the invariance of the laws of physics justified?

Is there any true inertial reference frame in the universe?


What is the difference between $\Lambda$ and $\Sigma$ baryons?

How can $\Lambda^0$ and $\Sigma^0$ both have $uds$ quark content?


How do we know quantum entanglement really happens?

How do we know that entanglement allows measurement to instantly change the other particle's state?


Pauli exclusion responsible for "solidity"?

How can I stand on the ground? EM or/and Pauli?


Can the universe have a definite energy density?

Is the total energy of the universe zero?


Is the Standard Model fully renormalizable?

What do we mean when we say 't Hooft proved that Standard Model is renormalizable?


If photons have no mass, how they create electrons and positrons on colliding?

Conservation of Mass during Electron - Positron Annihilation


Confusion about Length Contraction (ex in Muon decay)


If i use two or more lighters to heat an iron spoon, will it melt?


Why magnetic field are from south to north pole inside bar magnet?

What is the direction of magnetic lines of force inside a bar magnet?


It is possible to convert qubits to bits?


What will *actually* happen to an object moving through an event horizon?

Does a diatomic molecule falling into a black hole dissociate?


What is the math knowledge necessary for starting Quantum Mechanics?


Is Quantum teleportation possible for large objects like a cat, for example?


Is it the same time, does time pass at the same pace everywhere in the universe?

Doesn't dating the universe violate the concept of spacetime's inseparability?


After all "Is the gravity a force or not?"

If gravity isn't a force, then why do we learn in school that it is?


Direction of Friction of a cup on a table cloth

Consistent method for finding direction of static friction


How much kinetic energy does a helicopter use in a hover?

Calculate work done by a hovering helicopter over time


Is there an experiment showing that the warping of space affects the shape of an electrostatic field?

Are static magnetic and electric fields distorted by gravity? How?


Where does the extra kinetic energy of the rocket come from?


How light is able to choose the path to take?

How does light know which path is fastest?


Universe expanding - Interstellar space, Intergalactic space or Intersupercluster space?

Why does space expansion not expand matter?


How does sound change high in atmosphere?

What is the relation of sound propagation to air pressure?


Black holes and positive/negative-energy particles


How can anything ever fall into a black hole as seen from an outside observer?


How can an isolated system filled upto the brim with some fluid get more random?

For an isolated system, can the entropy decrease or increase?


Why does everyone seem to assume that gravitational waves will always be very small?

How close would you have to be to the merger of two black holes, for the effects of gravitational waves to be detected without instruments?


What determines which frames are inertial frames?


What will happen first: the rod's front end will hit the back wall of the cave or the left end of the rod will enter the cave?

Hole-and-nail paradox in special relativity


Quantum Entanglement - What's the big deal?


Which clock will dilate when one is moving towards the other


What is the Potential difference in $C_1$?


Is it mathematically impossible to incorporate the space curvature into the equations of motion and gravity?

Can general relativity be completely described as a field in a flat space?


If we solved the observer effect/problem, doesn't this mean Quantum superposition isn't actually real?

Isn't the uncertainty principle just non-fundamental limitations in our current technology that could be removed in a more advanced civilization?


Electrons residing in an orbit with energy lower than the ground state energy


Why is particle physics called high energy physics?

Why is 7 TeV considered as a big amount of energy?


Difference between position of indexes in tensor notation (SR)

Staggered Indices ($\Lambda^\mu{}_\nu$ vs. $\Lambda_\mu{}^\nu$) on Lorentz Transformations


How does Hawking Radiation not violate energy conservation?

Black holes and positive/negative-energy particles


Why do we think of a nucleus as nucleons held together by a strong force rather than a cluster of quarks?

How do we know that the nucleus isn't a quark-gluon plasma?


Does the life of a black hole violate baryon number conservation?

No hair theorem for black holes and the baryon number


Which predictions can a theory of quantum gravity make - update since 2014?

What predictions can a quantum gravity theory make?


Are holograms in midair physically possible?

Is it (theoretically) physically possible to project an image into thin air?


Constants of proportionality in Force Equations/ Physics in General

How do we know that $F = ma$, not $F = k \cdot ma$


Why doesn't the Earth lose its magnetic properties?

Why does the Earth not lose its magnetism?


What does the photon feel when it hits an asteroid on its path to earth

How does a photon experience space and time?


Why don't we avoid self-interaction terms when we measure energy of a continuous charge distribution as we do for point charge distribution?

Confusion about calculating electrostatic energy using the electric field


Derivation of formulas in Doppler‘s effect in light


Rotational kinetic energy when moment of inertia is changed


What will happen to the level of water when the ice melts?

Why does ice melting not change the water level in a container?


Touching is a Pauli exclusion principle or electrostatic force?

What does it mean for two objects to "touch"?


How can the red shift due to Hubble flow be consistent with the law of conservation of energy?

Photons in expanding space: how is energy conserved?


Why am I not getting the right values for the time it takes a spaceship to get to 0.9c?

Is there a formula that gives the position of an object depending on the time, but which doesn't allow the object to surpass the speed of light?


Is mass-energy conversion contradicting energy conservation?

Why can't I do this to get infinite energy?


What are the relativistic arguments for existence of space?

What is time, does it flow, and if so what defines its direction?


What does the identity operator look like in QFT, written in momentum eigenstates?

How to derive completeness relation in quantum field theory with a Lorentz invariant measure?


Why does the density of electric field lines make sense, if there is a field line through every point?


Electric Potential produced by Hollow Sphere


How does a rocket obey Newton's third law?

What is a rocket engine thrusting against in space?


What aberration causes the common "cross pattern" in astronomy images?


How can time dilation occur for one person but not another?

What is the proper way to explain the twin paradox?


Are photons and electromagnetic waves the same thing?

What is the relation between electromagnetic wave and photon?


Why we see water like effects (reflection) at some distance from the driving seat on a motorway in sunny weather?

Why does the road look like it's wet on hot days?


Where does the momentum exchange happen in a rocket?


Is the Earth orbiting an 'illusory' Sun, owing to the 'speed' of gravity?

Is Earth's orbit around the Sun affected by the ~8 minutes light delay?


Why does soap solution forms bubble but tap water does not?


Doesn’t gravity violate the first law of thermodynamics?


Why in quantum mechanics must orthogonal states stay orthogonal?


Why does a velocity that gives gravity's centripetal acceleration make you stay in orbit?

Why doesn't the Moon fall onto the Earth?


Does the mass of a brick increase when you lift it?

Does the mass of an object change as it moves away from the earth?


Space needed for expansion of the Universe

If the universe is expanding, what is it expanding into?


Why does violet (purple) color contain red component?

Why does light of high frequency appear violet?


How virtual photons give rise to electric and/or magnetic field?

Virtual photon description of B and E fields


How can one prove mathematically using a thought experiment that a simple pendulum will vibrate forever in an ideal condition (no friction)

Would a pendulum swing indefinitely in a frictionless vacuum?


Why is the cross product of vectors in the given image like this?

Why can the cross product of two vectors be calculated as the determinant of a matrix?


Interpretation of Moment of Inertia Tensor

What is the physical significance of the off-diagonal moment of inertia matrix elements?


Where does gravity get it's energy to cause tides?


The Zero Electricity Air Cooler : How does it work?

How does the Eco-Cooler air conditioner really work?


Why does the period of a pendulum decrease in an accelerating frame?


Matter moved faster than photons at big bang?


Negative Gravity Fields and Time Dilation

Would time speed up near a large body of negative mass relative to observers in micro gravity?


Why does a car moving in a circular track experience static friction if it is already in motion?

Directions of static & kinetic friction?


Why doesn't the LHC accelerate electrons?


What happens to the electric field lines when an electron and positron collide?

What happens when a field turns on or off?


How can $\hat p = - i \hbar \partial_q$ be derived starting from the definitions of $\hat q$ and $\hat p$ in terms of creation/destruction operators?

What is the most general expression for the coordinate representation of momentum operator?


Theta terms observable effects for $SU(3)$, $SU(2)$ and $U(1)$ in the standard model

Why is there no theta-angle (topological term) for the weak interactions?


Why does the inverse square law cause elliptical orbits?


Vortex in liquid collects particles in center


A doubt regarding Maxwell correction for Ampere's law

Was Maxwell's displacement current the only way to fix up Ampère's Law?


What is the cause of quantum entanglement?

Why is quantum entanglement considered to be an active link between particles?


Basic quantum mechanics- violation of the time-energy uncertainty principle by pure eigenstates of the infinite potential well?


Path of photon from Sun to earth unaltered?

Why do sunbeams diverge even though the sun is much more than a few kilometers away?


Why does holding something up cost energy while no work is being done?


What additional things should I do to understand language of science

How should a physics student study mathematics?


Boundedness of general relativity Hamiltonian


What is the mistake in calculating such a commutator?

What's wrong with this derivation that $i\hbar = 0$?


Peaks different in wavelength and frequency space

The strange thing about the maximum in Planck's law


What will happen if rotation of Earth will get reverse?

Would it matter if the Earth rotated clockwise?


What keeps electrons on a negatively-charged conductor from leaving?


How can light bulbs' flicker rates be found?

What invisible flicker do different types of light bulbs have?


What would happen if something *rotated* with a tangential velocity near speed of light?

What happens if a super fast rotating ball accelerates near speed of light?


Why do people float inside space station in space?


Why does an electron have left-handed and right-handed components?


How can a point-particle have properties?


If space time can ripple can it shear/tear/shatter?


Do the cold welds that cause static friction also affect the lifting force?

Lifting frictional force and relative values for kinetic vs static friction


Discrete structure of moving light in space-time. Does the light actually moving or it is triggered by cells of space-time?

Would time freeze if you could travel at the speed of light?


Is there a mathmatical theory to explain all physical phenomena?

Final theory in Physics: a mathematical existence proof?


How can one transform an arbitrary 2D metric to coordinates in which it's conformally flat?

Diffeomorphism & Weyl transformations in the 2D worldsheet of string theory and the existence of conformal gauge


force on a moving charge in magnetic field


Prove Spin of a massless particle $S_z=\pm1$

Why is the $S_{z} =0$ state forbidden for photons?


What is the temperate of a vacuum on earth?


Why is there isn't a Theory of everything after decades of research?

Why don't we have a theory of everything?


Let's say you are at the center of the earth witch way would gravity pull?

Would you be weightless at the center of the Earth?


What is the calculation of the Hubble time based on?

How does the Hubble parameter change with the age of the universe?


Hawking Radiation specific clarification

Why doesn't Hawking radiation cancel itself out?


How can electrons spin if they have no volume?

What is spin as it relates to subatomic particles?


Are Ross-Littlewood-sequences or negative probabilities possible in physics?

Does the Banach-Tarski paradox contradict our understanding of nature?


What do the arrows on this Feynman diagram represent?

Arrow and flow of charge in fermion propagator


Can someone explain in a simple manner that How can we use Quantum entanglement to transfer data instantly when we seperate photons?

Why is quantum entanglement considered to be an active link between particles?


If $v_{contact,road}$ in rolling motion is zero, how the contact point still manages to move forward?


If entropy decreases for cold systems, isn't the heat death of the universe a state of low entropy?

Does entropy increase or decrease as our Universe is expanding?


Hamilton's equations for Dirac Hamiltonian


Tangential component of electrostatic field on a charged surface?


Why can't gravity force an object past the speed of light?

Can gravity accelerate an object past the speed of light?


Why would spacetime curvature cause gravity?


How can corium eating its way into water tanks cause a megaton scale explosion?

How large would the steam explosion at Chernobyl have been?


In special relativity, how can time dilation happen from both point of view?


Why do balloons get cold when they deflate?

Rubber band stretched produces heat and when released absorbs heat.. Why?


Derivation using reduced mass for electron orbitals in the Bohr model

Why is a proton assumed to be always at the center while applying the Schrödinger equation?


Special relativity different time dilatation?

What if a light clock travels perpendicular to mirrors that make up the clock?


Doubts in an introduction to classical field theory

Is the Lagrangian density a functional or a function?


A paradox between quantum and statistical mechanics?

How is quantum mechanics consistent with statistical mechanics?


Why can't the wave function and it's derivative be zero at the same point?

Wavefunction and its derivative vanish at same point


Why is the length of the Kelvin unit of temperature equal to that of the Celsius unit?

Why is a degree Celsius exactly the same as a Kelvin?


How can we prove that light is an Electromagnetic wave?

Why is light called an 'electromagnetic wave' if it's neither electric nor magnetic?


Centre of mass of a solid cone using a symmetrical method

A teaser on center of mass of right circular cone?


Units of "mean free time" of a wave/particle


Simulteneity & Irrelevance of Frame Choice


Does the Einstein field equation uniquely determines the topology of spacetime?

What is known about the topological structure of spacetime?


Does all objects really fall with the same acceleration?

Don't heavier objects actually fall faster because they exert their own gravity?


Why does a water jet bend in a static electric field?

What does really attracts a water stream to a charged object?


Calculating the Commutation Relation of the Generators of $SO(n)$

Lie bracket for Lie algebra of $SO(n,m)$


Recommended books for advanced undergraduate electrodynamics


Can something travel faster than the speed of light?

Will an object always fall at an infinite speed in a black hole?


What is time, does it flow, and if so what defines its direction?


What type of displacement is virtual displacement? Is it really a displacement? How to calculate it?

Why is the d'Alembert's Principle formulated in terms of virtual displacements rather than real displacements in time?


What is the radius of the event horizon?


Angular acceleration of ball when falling

Does mass distribution/center of mass affect free fall?


Does gravity play a role in the Earth's equatorial bulge?

What is an intuitive explanation using forces for the equatorial bulge?


Shouldn’t the work done be zero in this case?

Work done when lifting an object at constant speed


Dirac delta function equation intuition and proof

The magnetic field of a magnetic monopole


Why spin 2 is related with attractive force?


Electric Motors: why do they draw more current when stalled, and less when moving?

Why does an electric motor burn up when you physically stop it?


Is magnetic field a consequence of electric field?

How do moving charges produce magnetic fields?


Why is energy quantized but mass is not?


Particle annihilation - mathematical description, equations governing it?

What is the mechanism of particle anti-particle annihilation


How can a horse move a cart if they exert equal and opposite forces on each other according to Newton's third law?

Given Newton's third law, why are things capable of moving?


Is density of an element directly proportional to atomic number or atomic weight?

Why is the relationship between atomic number and density not linear?


Why Electron Does Not Radiate In Bohr Orbits?

Why don't electrons crash into the nuclei they "orbit"?


Why is sliding friction more than rolling friction?

What is the cause of rolling friction? & why is it less than sliding friction?


Two apparent contradictions in SR involving time dilation and length contraction


Extrinsic Description of spacetime curvature, is it possible? How many dimensions would we need?

Can general relativity be explained by equations describing a fabric of space embedded in a flat 5-dimensional Minkowski space?


How do the laws of physics work in quantum system?

Is there an equivalent of computation of physical processes in nature?


How does a Venturi Injector comply with energy conservation?

Kinetic energy of fluids in Venturi Injector


Is it true that whenever any non rigid body moves, there must be a delay between the ends?

Is it possible for information to be transmitted faster than light by using a rigid pole?


What is the proper way to explain the twin paradox?


Notation on four-vectors using imaginary spacelike components

Minkowski's complex Euclidean space vs. the real pseudo-Euclidean version


Regarding accelerated charges produce electromagnetic waves

Will stationary charge radiate E.M waves if observer is accelerating?


Clarification on Rayleigh scattering causing various sky colors


How is linear momentum conserved after collision while part of linear kinetic energy contributes to angular kinetic energy

How can momentum but not energy be conserved in an inelastic collision?


If the method of FTL cannot be observed, does it still break causality

How does faster than light travel violate causality?


Does Maxwell's Equations on Magnetic Field holds good in year 2020?

How wrong are the classical Maxwell's equations (as compared to QED)?


I have some trouble with springs in series

Effective spring constant of springs in series


Why an object with a velocity of 11.2 km/s only enter space?

What is escape velocity? In reality, how can something no longer be under the gravitational influence of something else?


Equations of motion for an object with non-constant acceleration related to its velocity

Deriving equations of motion using integration


Is it possible to model spacetime as a function from an interval $I$ to a set $S$, where $t\in I$ represents time and $x\in S$ represents space?

What is the closest general-relativistic equivalent of a "time slice"?


How to identify progressive waves by their equation

How to determine whether a wave is travelling or standing?


Is electric current just the rate of flow of charges?

Displacement currents, aren't really currents?


Slinky reverb: the origin of the iconic Star Wars blaster sound


How to prove that path of a charged particle in a uniform magnetic field is circular or helical?

Helical motion of charged particle in external magnetic field


In counting degrees of freedom of a linear molecule, why is rotation about the axis not counted?


Energy-Time Uncertainty Relation and Virtual Particles

What is $\Delta t$ in the time-energy uncertainty principle?


If time is relative, then how is the age of the universe calculated?

Does the age of the universe depend on the way it is defined?


Photons of light are massless so how can they transfer momentum?

If photons have no mass, how can they have momentum?


Relation between energy, frequency and wavelength

Loss in energy by light after reflections


Is Newton's First Law an actual law, or just the definition of force?


Are colors grounded in physics or are they a matter of human perception?

What determines whether colors you can't see are visible or not?


How light travel in a vacuum or in an empty space?

Why don't electromagnetic waves require a medium?


If space expands, why does a liter of water stay a liter?

Why does space expansion not expand matter?


Raising and Lowering Indices of Basis Tensors?

Inconsistency with partial derivatives as basis vectors?


Why is energy proportional to light's frequency?

Does a single photon's energy depend on frequency? (photoelectric effect)


Deriving Schrodinger equation from Klein-Gordon QFT with the definition $\psi(\textbf{x},t)\equiv \langle 0|\phi_0(\textbf{x},t)|\psi\rangle$


If heat and sound are both caused by vibrations, why isn't sound warm? Or heat loud?


What is the physical meaning of a Supercharge?

What conserved quantity does Supersymmetry imply?


Does diffraction happen from small slit width than its wavelength?

What happens to waves when they hit smaller apertures than their wavelenghts?


Why does a bubble arise on an unevenness of a glass?

Why rough surfaces promote nucleation of CO2 in carbonated drinks?


How many degrees of freedom for $\rm N_2O_2$?

In counting degrees of freedom of a linear molecule, why is rotation about the axis not counted?


Proof of the existence of the energy-momentum tensor

Energy momentum tensor from Noether's theorem


Where I can learn Science as a whole? From nothing to relativity, thermodynamics, to quantum


Newton's cradle: why not twice the balls at half the speed?


Can black holes form in a finite amount of time?


The role of the "observer" in quantum theory?


Is temperature a Lorentz invariant in relativity?


Lagrangian for first order equation of motion?

Action principle, Lagrangian mechanics, Hamiltonian mechanics, and conservation laws when assuming Aristotelian mechanics $F=mv$


How do we see that the axion is a pseudoscalar?

How can I prove that the following Lagrangian is Lorentz-invariant iff the axionic field is a pseudoscalar?


How do you calculate the energy of an electromagnetic wave from its amplitude?


Redshifting of Light and the expansion of the universe


How does mirror reflect light (according to quantum mechanics)?

Explain reflection laws at the atomic level


Are black holes totally black and formed?


Why are the seasons reversed between the northern and southern hemispheres?


Need help understanding weird definition of pure states

Differences between pure/mixed/entangled/separable/superposed states


which give higher cooling rate , strong circulated water or thick copper plate?

which is more effective chilling for metal casting, thick copper die or water-cooled thin copper mold?


Wouldn't the thermodynamic cost of creating alternate universes make the Many Worlds interpretation implausible?


How do single photons travel from here to there


How are the predictions of the Schwarzschild solution consistent with our observations of black holes?

Can black holes form in a finite amount of time?


How does physics know something is spinning or rotating?

How does a spinning object "know" that it is spinning?


Update: Does the Planck scale imply that spacetime is discrete?


How does the Uncertainty Principle work?

Is the uncertainty principle a property of elementary particles or a result of our measurement tools?


Can there be temperature inside of a massive Black Hole?


Are the effects of general relativity accounted for in the calculation of the trajectory of the PARKER probe?

Parker Solar Probe passing extremely close to the Sun; what relativistic effects will it experience and how large will they be?


How is the "charge on a capacitor" defined when two plates are unequally charged?

Capacitor with different charges on each plate


Why the eigenvalues of orbital angular momentum $L$ never take half-integral values?

Half-integer eigenvalues of orbital angular momentum


Why is force invariant under a Galilean transformation?

A question concerning the Galilean invariance of Newton's laws


How can you explain long lifetime of the Rydberg atoms?

How to explain the long lifetime of Rydberg atoms with Fermi golden rule?


What is the reason for Moon and satellite in free fall condition?

Why doesn't the Moon fall onto the Earth?


What is the proper way to explain the twin paradox?


Why is it easier to ride a bicycle than to run?

What makes running so much less energy-efficient than bicycling?


Why the galaxies form 2D planes (or spiral-like) instead of 3D balls (or spherical-like)?


would connecting a pipe that can carry twice the volume of water to a supply pipe reduce the water pressure in half? If not is there a formula?

Calculation of pressure from flow rate of water


Why do we regard $z$ and $\bar z$ as independent in CFT?

Decoupling of Holomorphic and Anti-holomorphic parts in 2D CFT


Why doesn't the Young's modulus change when an alloy is strengthened?


Can the laws of mechanics be framed without invoking coordinate systems?

Classical mechanics without coordinates book


A doubt regarding Planck's quantum theory


Computing gravitational acceleration with General Relativity

How does "curved space" explain gravitational attraction?


Is it reasonable and common to interpret $dt$ as a time point (a point in time)?

Difference between $\Delta$, $d$ and $\delta$


Time dilation and twin paradox - can this be explained in plain English?


What does phase velocity physically represent, and why can it be superluminal?

In superluminal phase velocities, what is it that is traveling faster than light?


Equivalence Principle: Why is sitting in space the same as failling in a uniform gravitational field

Why does a free-falling body experience no force despite accelerating?


Quantum Electrodynamics explanation for refraction

How are classical optics phenomena explained in QED (Snell's law)?


Effect of air resistance of the period of a pendulum

Does damping force affect period of oscillation?


Is it true that we are probably Boltzmann brains?

Is the Boltzmann brain problem really clearly established as a problem?


Flame shape and size (length) depending on gravity


Does dark matter interact with baryonic matter only through the gravitational field?


White cloud around fighter jet at Supersonic speed

Why do vapour cones form around jet fighters?


How can a droplet of liquid float on the surface of the same liquid?


Recommendations for statistical mechanics book


Given this graph from Wikipedia concerning the cosmogenic origin of each element, how are Lithium, Beryllium, and Boron formed from cosmic rays?

Do supernovae produce an appreciable amount of lithium?


Why and how is the speed of light in vacuum constant, i.e., independent of reference frame?


Why do the magnetic poles of the Earth get reversed?


Strange roughness feeling on electrically ungrounded surfaces

Why does my wife's skin buzz when she's using her laptop?


Why can't humans throw as fast as bullet and what law is involved?

Why can't humans throw objects at bullet speed when the force involved seems so small?


Is the Big Bang occurring or did it already occur (a question about time)

What is time, does it flow, and if so what defines its direction?


Why don't solstices coincide with temperature extremes?

Why is the summer, in the temperate latitudes, in average, hotter that the spring?


Probability in QM: derivation or interpretation?


Intuitive explanation of Archimedes' principle?


Why is it easier to get sunburnt in the water?


Why does most galaxies resemble a 2 dimensional plane?

Why the galaxies form 2D planes (or spiral-like) instead of 3D balls (or spherical-like)?


Physics behind seemingly-impossible "rice bowl suction" Guinness world record?


Why must $v$ be $< c$ in the Lorentz transformations? Do these equations not apply to light?

Would time freeze if you could travel at the speed of light?


Why do I always hear remote train horn at night?


Macroscopic quantum coherence in classical electromagnetic field

Are coherent states of light 'classical' or 'quantum'?


Is "quantizing" a field different from "quantizing" a particle?


Why do we use Hermitian operators in QM?


Lagrangian of classical electromagnetism without $A_{\mu}$ field

Least-action classical electrodynamics without potentials


How is one element capable of radiating (almost) every wavelength?

What are the various physical mechanisms for energy transfer to the photon during blackbody emission?


Does an electromagnetic wave necessarily contain many photons?

What is the relation between electromagnetic wave and photon?


Immediately after the Big Bang, was the universe in a state of extremely low or extremely high entropy?


Unphysical degrees of freedom in the Yang Mills Lagrangian

How many physical degrees of freedom does the $\mathrm{SU(N)}$ Yang-Mills theory have?


If quantum entanglement is not an active link between particles, then how did China transmit data via Earth-to-space quantum entanglement?

Can someone explain in a simple manner that How can we use Quantum entanglement to transfer data instantly when we seperate photons?


Equipartition of energy and degrees of freedom in Diatomic gas

7/2 versus 9/2 for diatomic heat capacity


Heating effect of electric current: Will this really happen?


Could you generate a lot of electricity in space?

Would a generator in vacuum/space provide electricity endlessly?


Why do we prefer "Lagrangian and Hamiltonian mechanics " over the newtonian mechanics?

What is the difference between Newtonian and Lagrangian mechanics in a nutshell?


Alexander Vilenkin - The Universe probably had a beginning


Concerning the passage of light through a glass medium and it's apparent re-acceleration, is the absorption explanation supported by evidence?

What really causes light/photons to appear slower in media?


Can a body be in equilibrium when only one force acts on the body?

When a ball is tossed straight up, does it experience momentary equilibrium at top of its path?


Why don't electrons crash into the nuclei they "orbit"?


What's the point of Hamiltonian mechanics?


Why don't electromagnetic waves require a medium?


In electrostatics, why the electric field inside a conductor is zero?


Mathematical proof that Fermions are half-integer spin particles, and half-integer spin particles are Fermions

Why bosons have integer spin and fermions have half-integer ones?


Where do ultrahigh-energy particles come from?

Where do ultra-high-energy cosmic rays come from?


Why is the shape of lightning or an electric spark a zig-zag line?


What are the relativistic implications of building an arbitrarily tall tower on the equator?

Rotate a long bar in space and get close to (or even beyond) the speed of light $c$


Why centrifugal force (not centripetal force) is considered while deriving the effect of rotation of Earth on "g"?


Electric force much stronger than gravitational force?

What does it mean to say "Gravity is the weakest of the forces"?


Why can't the Schrödinger equation be solved exactly for multi-electron atoms? Does some solution exist even in principle?

What are the primary obstacles to solve the many-body problem in quantum mechanics?


In connected motion, arent the tension of string and weight of body action and reaction forces? so shouldnt they be equal in magnitude?

Tension force in a rope bringing down a mass


(2+2)-dimensional flat spacetime with neutral signature


How to compute entropy of networks? (Boltzmann microstates and Shannon entropy)


Moving from eigenstate basis of a Hamiltonian back to operator basis

Do the ladder operators $a$ and $a^\dagger$ form a complete algebra basis?


Can anyone explain me how time can bend according to Einstein in simple way?

How exactly does curved space-time describe the force of gravity?


What happens to sound at speeds greater than mach 1?