Does This System Of Electric Charges Violate Conservation Of Energy?

Perpetual motion in electric dipole restricted to a circular path with a charge at the centre


What is a mode in electromagnetic theory

Understanding of a" Mode" in Optical Fibers


Better explanation of the common general relativity illustration (stretched sheet of fabric)


Young's double slit experiment and obliquity factor

How position of source affects YDSE interference?


Wave energy in terms of classical and quantum mechanics


Hamiltonian definitions in the presence of boundary term

What canonical momenta are the "right" ones?


What prevents this magnetic perpetuum mobile from working?


Can current be induced in a superconductor?


Black Body radiation curve - Does it depend only on temperature.?


What is acceleration due to gravity at the centre of the earth?


The Many-Worlds interpretation of Quantum Mechanics

Many-worlds: how often is the split how many are the universes? (And how do you model this mathematically.)


Why do I need energy quantization to explain the blackbody spectrum?

How can blackbody radition be explained by quantization?


Does a battery 'excites' current to flow in a superconductor?

How can I put a permanent current into a superconducting loop?


Does the positron prove that Dirac's electron sea must exist?

What was missing in Dirac's argument to come up with the modern interpretation of the positron?


What happens if we exert more force on an object which would be travelling at near maximum light speed?

Does the pilot of a rocket ship experience an asymptotic approach to the speed of light?


Why are water waves transverse or up and down?

Why can't transverse waves travel through a liquid?


Why do high frequency waves have high energy

What's the difference between low energy photons and high energy photons?


Euler-Lagrange equations using $\vec{E}$ and $\vec{B}$ instead of $A^\mu$

Least-action classical electrodynamics without potentials


Huge confusion with Fermions and Bosons and how they relate to total spin of atom


How would you calculate the force of a hammer hitting an anvil?

Good way to compute the force of a hammer blow?


Destructive Interference of two wave pulses

Why does destructive interference not stop a wave?


What shape has the highest drag coefficient?


Understanding which string breaks when one pulls on a hanging block from below


How can the universe expand faster than the speed of light?


Expectation values of odd operators in case of even potentials are zero?

Expectation values of the position operator is equal to zero in case of even potentials?


why is friction acting towards the centre in a level curved road?


Why are there no loop corrections to the photon mass?

What prevents photons from getting mass from higher order Feynman diagrams


Applying the Heisenberg uncertainty principle to photons

Application of Heisenberg's uncertainty principle on photons


Energy conservation of Virtual Particles - Quantum Fluctuation?


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


Why the SUSY particles of fermions have spin 0 but not 1?

Supersymmetry: spin of the superpartners


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


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


Why does a wave reflect on the edge of an open tube?

How can standing waves be produced in an open organ pipe if the ends are open?


How energy is conserved in destructive interference of plane waves?

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


Does this paper falsify the vacuum energy?

Are dark energy and zero-point energy the same thing?


Will gravitational field of a body increase if the body is accelerated?

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


Uniqueness of Lagrangian and Hamiltonian

Do the same equations of motion imply the same Lagrangians?


Does all hydrogen originate from the Big Bang?


Why can we use Gauss' law to show that the field inside a spherical shell is zero?

Why is the electric field zero inside a hollow conducting sphere?


The secret behind the spinning, asymmetrically weighted, 2D disk-shaped top?


What causes a steel gurney to accelerate towards an MRI machine?

Why does magnet attract iron but not other metals?


Is it possible to rotate a very very long (almost infinite) and rigid pole such that its end reach the speed of light?

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


In which situation(s), if any, would two balls of differing mass actually hit the ground at the same time?

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


Why does ohms law not work on transformers?


Why we are not using Lagrangian instead of Hamiltonian in non-relativistic quantum mechanics?

Why not use the Lagrangian, instead of the Hamiltonian, in nonrelativistic QM?


Can we have a black hole without a singularity?


Is the light escaping from a massive star held back a bit by the pull of gravity, or by the warping of spacetime near it?

Speed of light in a gravitational field?


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


Does $E=mc^2$ apply to electron shells with different energies?

Does the mass of an electron change with its "energy state"?


If things never travel in straight paths, was the measurement of speed of light 'accurate'?

What is the trajectory of a photon moving through a vacuum?


5 Lagrangian points: why isn't there a line of stability between $L_1$ and $L_4$ and $L_1$ and $L_5$ respectively?


Why is the pressure on the ground equal to the weight of the atmospheric column on it?

Why does atmospheric pressure act on us?


How are physics theorems so accurate, relative to fixed measurement systems?

Why isn't it $E \approx 27.642 \times mc^2$?


Why is the curl of magnetic field $0$ outside the conductor and non-zero inside?


Entanglement and the relativity of simultaneity: an experiment

The choice of measurement basis on one half of an entangled state affects the other half. Can this be used to communicate faster than light?


Influence of delta potential (particle in a box)

Delta function potential in an infinite square well


Recommended books for advanced undergraduate electrodynamics


Why are diamond shapes forming from these evenly-spaced lines?

Why do I see a saddle in this picture of a computer screen?


What is the generalisation of the wave differential equation in curved spacetime?

The wave equation in general relativity, special relativity, and Cartesian coordinates


How sharply does the wavefunction collapse upon measuring position?

How does wave function collapse when I measure position?


What is a good book for learning quantum mechanics with mathematical derivations?

What is a good introductory book on quantum mechanics?


Euler's equation for rigid body rotation applied to inertia frame, with body frame both rotated and translated with respect to the world frame


Why can curved spacetime be locally a Minkowskian spacetime?

How can a point-like particle "feel" gravity, if locally the curvature of spacetime is always flat?


Why cannot we add gravity in quantum mechanics without additional dimensions as done in bosonic or superstring theory?

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


Why don't we observe quantum effects for large massive objects at rest?

Uncertainty principle for a sitting person


How to check the particle rate of $1\ m^{-2}.s^{-1}$ at an energy of $10^{12}\ TeV$ from the "Swordy plot"?

How do you convert between different units of particle flux?


Why is electric flux due to a point charge placed at the face of a hemishpere, cone and cube the same?

Using Gauss's law when point charges lie exactly on the Gaussian surface


Photoelectric experiment explaining particle property of light

Why wave theory cannot explain photoelectric effect and provides evidence for particle nature of light?


Book (0.25kg) at rest on table.Force that Earth exerts on book is equal in magnitude to force that book exerts on Earth as this is Newton 3rd law pair


Calculating the number of bound states in a finite 1-D potential well varying according to the depth of the well

Energies and numbers of bound states in finite potential well


What is the physical difference between maximally mixed and maximally entangled bipartite states?

How is quantum superposition different from mixed state?


Why does the Hadamard act as $H^{\otimes n}|x\rangle = \frac{1}{\sqrt{2^n}}\sum_{y\ \in\{0,1\}^n}(-1)^{x_1y_1+···+x_ny_n}|y\rangle $?


Can the wave function of a particle be any function?


How does relativity explains time-dependent behaviour for objects not experiencing time?

How does a photon experience space and time?


How to solve these kind of electric circuit?


Is there a proof that the set of real numbers can exactly represent distances?

Why is physical space equivalent to $\mathbb{R}^3$?


Why can't we make a perpetual motion machine by using a magnet to pull up a piece of metal, then letting it fall back down?

Why doesn't this magnetic perpetual motion machine work?


Wave simulation without reflection on the boundaries

What boundary conditions in a wave simulation would avoid reflections?


If a photon doesn't experience time, how can it have a frequency?

How can a photon oscillate when it experiences no time?


Why does current density have a direction and not current?


What is Lagrangian mechanics? And how is it different from Newtonian mechanics?

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


How does the buoyant force on a cube at the bottom of a tank of water manifest itself?


Basic Index Raising and Lowering Question

The Electromagetic Tensor and Minkowski Metric Sign Convention


Experimental justification for modelling electron as point instead of charged shell?

Experimental boundaries for size of electron?


Reaching 99.9% of the speed of light $c$ at 1G acceleration

Does the pilot of a rocket ship experience an asymptotic approach to the speed of light?


New to quantum physics, where should I begin from?

What is a good introductory book on quantum mechanics?


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


Is (velocity=angular rotation*radius) dimensionally homogenous?


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


How to grasp the limits of these two integrals?

Bessel function representation of spacelike KG propagator


Twin paradox - is acceleration relative?


Can an electron inside an atom annihilate?

Can vacuum fluctuations change the position of an electron?


Can there be conservation laws without a corresponding symmetry?

Is the converse of Noether's first theorem true: Every conservation law has a symmetry?


Why does a force not do any work if it's perpendicular to the motion?


Energy balance of this machine is positive. What is wrong?

Why doesn't this perpetual motion machine using the buoyant force work?


Variation Of Saturation Current in Photoelectric Effect

Why doesn't saturation current in the photoelectric effect depend on the frequency of light absorbed ny the metal emitter?


Is there a relation between the pressure at a point in a fluid and the pressure on the surface of a horizontal object placed at the same point?

If I immerse a coin in a cup of water, help me define the forces acting on it


Why is the speed of sound in air constant (relative to temperature) when the wave speed formula is Vwave = fλ?

Oscillation of air particles and speed of sound wave


Physical reason behind the origin of shock waves in astrophysics


Conversion of mass to energy in chemical/nuclear reactions


With drag, why does it take longer for an object thrown upwards to fall back down than it does for it to reach its highest point?

Time of a ball going up and down with air resistance


Why do nodes exist in wavefuncions of electrons?

Electron shells in atoms: What causes them to exist as they do?


Is it possible to observe interference from 2 independent optical lasers?


Why is the work done by friction zero when body is rolling?

How can friction do no work in case of pure rolling?


Discussion about a new nuclear fusion design

Nuclear Fusion with extremely high pressure and low temperature


Nothing can ever go through the event horizon of a black hole

Can black holes form in a finite amount of time?


Why do people think that rockets can thrust in the vacuum of space?

What is a rocket engine thrusting against in space?


How is reflection of light possible at all?

Does light accelerate or slow down during reflection?


Why does Stirred (rotating) coffee alters cup’s resonance frequency?


Is there a contradiction between isotropy and the Big Bang?


Can we also Legendre transform the Lagrangian using $\frac{\partial L}{\partial q}$ instead of $\frac{\partial L}{\partial \dot q}$?

Why do we use the Lagrangian and Hamiltonian instead of other related functions?


How do we perform transverse measurements in a two level system?


Why does a stable orbit of $H$ atom contain an integer number of de Broglie wavelengths?

Why can't an energy level exist containing 0.9 electron wave wavelengths? Why must it be a whole number?


Expanding electromagnetic field Lagrangian in terms of gauge field


Why do we believe local gauge invariance (that tells us photons are exactly massless)?

Is it experimentally proven that photons travel at speed $c$ in vacuum?


The twin paradox and positively curved space


Why does current always go to the resistance which is lower?

How do electrons know which path to take in a circuit?


What devices are used in a proton accelerator to separate the protons from their electrons and send the protons into the vacuum chamber?

How are the protons for collisions in the LHC made?


How much more damage is caused after hitting a brick wall at 100mph over 50mph?

Please help understanding the difference between force and kinetic energy for an object hitting a wall?


What would the effects be on the world if light slowed down?

Is it possible to speak about changes in a physical constant which is not dimensionless?


Is it speed or acceleration that leads to time dilation?

Does velocity or acceleration cause time dilation?


Why Li is not added as contact by ion implantation method in p type HPGe detector?

Why n+ contact of p type Ge is 700um thick compared to p+ contact of n type Ge only 0.3um?


As space expands does the density of matter remain same or increase?

Why does space expansion not expand matter?


Time required to traverse a tunnel through the centre of a planet

Why are these periods the same: a low earth orbit and oscillations through the center of the earth?


Understanding Quantum Mechanics in short term

What's the standard "roadmap" to learning quantum physics?


Why does an interferometer with mirrors even work?

LIGO flawed by the identical expansion of laser wavelength and arms in presence of a gravitational wave?


Why do physicists believe that there exist magnetic monopoles?


Why is it necessary that different observers agree on the value of the spacetime interval $ds^2$?

Do we know why there is a speed limit in our universe?


Simplest GR geometrical model for bending of light


Why do accelerations due to gravity and external forces get added during upward motion?


What would torsion in spacetime look like?

Can the torsion of a connection be measured mechanically?


What is the true quantitative definition of "force"?

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


Why are you accelerating yet remaining at a constant speed while going around a curve?

Why does a perpendicular force not change speed?


Electromagnetic radiation: Why lower energy radiation( like radio waves) penetrates walls and higher energy radiation(like visible light) doesn't?

Electromagnetic wave properties of light vs radio waves


Need of describing the term acceleration


Speed of a current passing through a wire

How does electricity propagate in a conductor?


Isn't causality a disproof for the Copenhagen interpretation

A meaningful distinction between determinism and causality


How can multiple fermions combine to form a boson?

Can bosons that are composed of several fermions occupy the same state?


What am I missing about the paradox between relativity and quantum mechanics?

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


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


If A Very Distant Galaxy Has Never Been Observable By Us, Then It Never Will Be?

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


How could an ideal conductor with 0 resistance conduct electricity?

How can there be a current and an electric field in an idealized wire with no voltage drop?


What does bent in space-time means exactly? How does mass of an object affect space and time?

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


Why is light, that was emitted right at the big bang (same time/place), arriving to us at different times


What was Newton's own explanation of Newton's rings?


Will ideal voltmeter show any deflection in its needle?


Possible proof that the universe can not have infinite mass?

Is the total energy of the universe zero?


How is Newton's third law not valid in special relativity while momentum is still conserved?

Newton's third law and General relativity


Equivalence principle and inertial frames

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


Block Sliding Down a Plane (Perpendicular Velocity)


Time-evolution operator written through a commutator

Time ordering operator if commutator is $c$-number function


How much time dilation are we experiencing here on Earth?

Galactic Rotation Speeds - Ehrenfest Paradox, Gravitational time dilation, Dark Matter - all of the above?


How to see if certain representation of $SU(2)$ is symmetric/antisymmetric/mixed?


Conformal Transformation and angle preserving

Simple conceptual question conformal field theory


Why does the negative sign arise in this thermodynamic relation?


Shortcut to a problem based on toppling using D'Alemberts Principle

D'Alemberts Principle to solve a Classical Mechanics problem


How to solve circuit in static electricty?


Can we meaningfully talk about the size of an elementary particle irrespective of its quantum state?


Why is tension in string different for pulley having mass?

When do we assume that a rope has different tensions in different places?


Why pressure is considered as scalar quantity?

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


Why does a floating object displace more substance than a sunk object?

Basic buoyancy question: Man in a boat with a stone


What is speedlight travel "really" like (for a photon)?

Does a photon in vacuum have a rest frame?


How does the average kinetic energy of a spray can decrease?


Is it possible to break the second law of thermodynamics regarding entropy?

Is a spontaneous decrease in entropy *impossible* or just extremely unlikely?


Can a "lightsaber" be scientifically possible?


On the derivation of the Euler-Lagrange equations

Why are D'Alembert's Principle and the Principle of Least Action Related?


Derivation of Newton's law of gravitation

How was Newton able to guess that gravitational force is inversely proportional to distance squared?


How to obtain the distance traversed by a free falling body equation?


Can a body which is in pure rolling move forever?

Consider a horizontal surface with or without friction. Ideally, will a wheel rolling without slipping roll forever in both cases?


If voltage is same in two points why does electron move?

How can there be a current and an electric field in an idealized wire with no voltage drop?


Is there such a thing as a white laser pointer?

Why is making a laser that shines light over the full spectrum, i.e. a 'white laser', so difficult?


Any good resources for Lagrangian and Hamiltonian Dynamics?


Is the speed of light universal for all mediums?

What is the mechanism behind the slowdown of light/photons in a transparent medium?


Unjustified claim in Kittel about Bloch functions


Effect of dielectric on electric field outside the dielectric

What is the force between two charged objects when the space between them is partially filled by a dielectric medium?


Why is Compactification restricted to Toroids, Calabi-Yau et al?


Near Earth vs Newtonian gravitational potential


Work done in rotating a dipole in NON uniform electric field

Work done in rotating electric dipole in uniform field


In a Lithium Ion battery (during discharge) positive Li Ions flow to the +3.8 volt cathode. Where do they get the energy to climb that 3.8 V hill?

Why does Li+ ion move to cathode in Li-ion battery?


Wave Nature of Matter in the Macroscopic World

Quantum properties of objects with zero velocity


Does the Big Bang have the absolute lowest amount of entropy?

What was the entropy of the universe at the time of the Big Bang?


Regarding number of degrees of freedom of a dynamical system (as well as it's relation to number of equations of motion)

What is the definition of how to count degrees of freedom?


Lorentz invariance of Action or Lagrangian?

Lorentz invariance of the integration measure


Why does work depend on distance and not time?

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


Self-study book for dynamical systems theory?


Does the concept of infinity have any relevancy or application in Physics and applied Physics?


Who applies the force on the things moving backward that we see when moving forward?

A bob hanging in an accelerating train moves backward. What is the force moving it backward?


2 points of same potential in a single circuit

Basic questions about voltage drop in DC circuit


Is the result of the product of metric tensors $\eta^{\mu\nu} \eta_{\mu\nu} = 1$?


Deriving buoyant force from first principles


Special Relativity - Reference Frames S and S′ relative velocity

Special Relativity - Reference Frames $S$ and $S'$


Differences between the variations in Noether's theorem and Hamilton's Principle

Why is the symmetry variation $\delta_s q$ different from the ordinary variation $\delta q$?


What force provide tangential velocity change in whirling block problem?

How can tangential acceleration from a radial force be explained?


What induces electric field that drives current through whole circuit

The electric field should be in circular coil. But why do current flows in whole circuit?


What is the difference between a bound state and a resonance state?


Why don't we consider internal forces for motion?


Is this expression for the energy of a three-body system correct assuming Newtonian mechanics?

Double counting potentials in $N$-Body Problem?


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?


Is the quantum analogue of electrostatic field photon? What will be its wavelength then?


How can we be sure if Universe has exploded with big bang? Can't it be implosion?


Why are there dark lines in an absorption line spectrum from the Sun?

Why don't absorption and emission lines cancel out in our Sun?


Klein-Gordon-Equation provides a Scalar Theory that doesn't contain Spin


How do we know the age of Cosmic microwave background?


Why are action principles so powerful and widely applicable?

How general is the Lagrangian quantization approach to field theory?


The theater, the actors and the 'graviton'

Nature of gravity: gravitons, curvature of space-time or both?


Is (rest) mass conserved in special relativity?


Force, work and the apparent disappearance of Mechanical Energy

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


Understanding causality violation of tachyons in space-time diagrams

How does faster than light travel violate causality?


What is the significance of the second derivative of a function?


Current in circuit after joining two inductors with different currents through them


Pulling quarks from one another creates a new pair of quarks?


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


Photons in expanding space: how is energy conserved?


How can tangential acceleration from a radial force be explained?


Time dilation when observed from each frame


Can it be that apparent faster than light speed of shadow/laser dot is not actually faster than speed of light?

Is it really possible to break the speed of light by flicking your wrist with a laser pointer?


Can we simulate whole universe with infinite size of RAM and modern computer?

Can we simulate the whole universe in computer?


Would humans die of old age on an interstellar/intergalactic voyage?

How long would it take me to travel to a distant star?


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


How does matter know to obey physical laws?


Ladder operators applied to magnetic quantum number


If electrons are waves, how do they repel each other?


When and why is $\frac{d}{dt}\delta q^{i}=\delta \frac{dq^{i}}{dt}$ true?

Lagrangian Mechanics - Commutativity Rule $\frac{d}{dt}\delta q=\delta \frac{dq}{dt} $


Is it possible that the particles can be brought by some external agency without changing the kinetic energy?


What force does the dynamometer show in this case?


Would many extremely fine (solid) granules exhibit similar properties as a fluid?


Is the escape velocity of black hole greater than the speed of light ? If not, then why does light can't escape the black hole?

If the speed of light is constant, why can't it escape a black hole?


Direction of H and B inside and outside a bar magnet


How does the light and energy breakdown depend on wave frequency?

Frequency dependence of electromagnetic reflection


At what height should I drop my kids from to prevent getting splashed?


How do we know if quantum black holes were made in the LHC?

The Large Hadron Collider and Black Holes


Resource recommendation for Introduction to Nuclear Physics


What does having an imaginary part of potential imply?

Quantum mechanics - how can the energy be complex?


Why does a Ball bounce back if Forces are Equal and Opposite?


Can lightning be used as a source of energy?

Can the lightning be captured and used as power source?


Black holes and positive/negative-energy particles


Why are radians more natural than any other angle unit?


What is the shape of the quark structure in a proton or neutron?


Is there an alternative to Fock Space and Hilbert Space in quantum field theory?

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


Can we express any metric as Minkowskian metric if we adding more dimensions?

Can a non-Euclidean space be descripted through an Euclidean space of higher dimension? So why use non-Euclidean?


Is there any relationship to light and gravity since both propagate at the same speed in a vacuum?


Time Period of a damped physical oscillator

Does damping force affect period of oscillation?


Question about the position of electron and it mass


The Uncertainty Principle and Mach’s principle


How can wifi penetrate through walls when visible light can't?


Friction cause a car to acceleration AND also to stop?


When we charge a capacitor via a battery then why does exactly $1/2$ of the work done by the battery get converted to heat?

What happens to half of the energy in a circuit with a capacitor?


If electrons can be created and destroyed, then why can't charges be created or destroyed?

If Energy can be converted into mass, why can it not be converted into charge?


Does kinetic energy affect temperature of an object?


Time Slows Down or Speeds Up for the Traveler According to Special Relativity?


Does relative work done affect temperature of a body?

Temperature and kinetic energy of molecules


What does negative $\mu$ physically means?

Meaning of the chemical potential for a boson gas


What is an example of a matrix that does not represent a tensor of rank $2$?

Are matrices and second rank tensors the same thing?


Time dilation explained using a light-pulse clock

Time dilation clock experiment: what would happen if the clock were flipped 90 degrees?


Why can’t we accelerate photons, and is it possible for a photon to have mass?

Why don’t photons interact with the Higgs field?


How could the early Universe have low entropy when it was so compact?

Why was the universe in an extraordinarily low-entropy state right after the big bang?


Why is the equation for friction so simple?


If force is a vector, then why is pressure a scalar?

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


Are my arms pulled outwards when I sit on a rotating office chair?

Would there be centrifugal force if I were alone in the universe?


Has anyone ever created a formal system for quantum mechanics?

Are certain fields of physics axiomatized?


Why the eigenvalues of hamiltonian are discrete in bounded systems (only discrete energy levels)?

Discreteness of set of energy eigenvalues


The speed of light and the increase of relativistic mass

Does the (relativistic) mass change? Why?


If time stops at the speed of light, how do photons vibrate in waves

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


Elementary particles and halo of matter - rookie question

Why isn't dark matter just ordinary matter?


Why does it seem like a broken magnet's poles flip?


When I calculate the momentum of something what does the answer mean?


Current in series resistors and voltage drop in parallel resistors


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


Definition of Hamiltonian in Quantum Mechanics

Why can't $ i\hbar\frac{\partial}{\partial t}$ be considered the Hamiltonian operator?


Comprehensive book on group theory for physicists?


Would Schroedinger's cat smell 50% like death?

What counts as "observation" in Schrödinger's Cat, and why are superpositions possible?


Can the rate at which time passes be changed?

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


How age of universe or galaxy estimated?

How has the age of the Universe been derived from the observations made by the Planck mission?


What forces make objects fly away from the axis of rotation?

Is the force which throws a body on a rotating disk outwards centrifugal force?


Why do reflections on a rough surface stretch from the light source towards you instead of spreading out in all directions?

Why does sunset over a body of water cause a path of light stretching towards the horizon?


How is the weight of the body, zero at the centre of the earth?

Would you be weightless at the center of the Earth?


How much water can an object raise after its fall?


Could you escape a black hole - using a black hole?

Can we exit the event horizon of merging black holes?


Polarization of light using QM principles


How can any speed be defined as a constant?

If all motion is relative, how does light have a finite speed?


How do entangled states increase computational space for quantum computers compared when only using product states?

Why is quantum entanglement so important in the context of quantum computation?


Why do photons follow specific path after reflection from a mirror surface if they can be emitted in any direction by electrons of mirror surface?

Explain reflection laws at the atomic level


Can we construct a system in which two distinct paths give the same actions? If so, how does the system evolve?

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


Maxwell's equations in vacuum - EL in tensor notation

Retrieving Maxwell's equations from the minimum action principle


Why does frequency remain the same when waves travel from one medium to another?

Why doesn't the frequency of light change during refraction?


What exactly is the cosmological constant?

What does the 'cosmological constant' represent?


Is the magnetic monopole the same than the electric charge?

Why do physicists believe that there exist magnetic monopoles?


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?


Why does the current stay same everywhere in a series circuit

Why current in series circuit is the same?


Magnetic Field in the presence of a conductor


Do bodies moving at (near) light speed produce gravity?

Are moving objects producing stronger gravity fields?


Understanding Gauss’ Law in differential form for a point charge

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


How is it possible for a graviton to drag time frames and dilate time?

Nature of gravity: gravitons, curvature of space-time or both?


Taylor series for unitary operator in Weinberg


Why is $\oint_S \mathbf{E}\text d\mathbf{s}=q_{in}/\epsilon_0$ valid when finding electric field inside charged sphere(charges are inside sphere)?

Why can charges outside be ignored in Gauss's Law?


What really determins the color of light?

What determines color -- wavelength or frequency?


Why aren’t the electric and magnetic components of an EM wave complementary?

If time-varying electric and magnetic fields originate each other, how come they are in phase?


If a sphere is rolling down a friction-less incline surface, does it not roll?

What will happen to a ball kept on a frictionless inclined plane?


Sign of Work and potential energy in electrostatics


What arguments did Maxwell use to add the extra term in Ampère's original law?

What was the improvement that Maxwell did to the electromagnetic field equations and why?


Is it possible to represent gravity as a force field?

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


Difference between electric and magnetic force

Mechanism by which electric and magnetic fields interrelate


Can one of Newton's Laws of motion be derived from other Newton's Laws of motion?


Why does force along center of mass produce translation motion?

Why does a body not rotate if force is applied on the centre of mass?


Which is the biggest object which can interfere with itself?


Dot product between momentum and position $ \langle p|x \rangle$

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


Magantism vs Gravity with Special Relativity

Geometric interpretation of Electromagnetism


Angular momentum and conservation of energy when sitting on a spinning chair

What happens to the rotational kinetic energy?


Why doesn't static friction point down the incline on a ball rolling down an incline?

The direction of frictional force in smooth rolling motion


Relation between magnetic moment and angular momentum -- classic theory


How does planking burn calories if there is no force * distance?

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


Is the static friction greater or less than the kinetic friction when an object is moving? Why?

Why are there both Static and Kinetic Friction?


Why can't a particle rotate about its axis?

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


Is there a "standard" quantum simulator/animator for pedagogy?


Earth rotation: What provides the energy?

How do the Planets and Sun get their initial spin?


Speed of light in a gravitational field?


How does quantum entanglement help us communicate?

can we transfer data via quantum entanglement (likewise we communicate today) to a specific target


Can we lock the light (photons) up inside a box? Why / Why not?


Does a photon in vacuum have a rest frame?


Schwarzschild metric of a moving observer

Gravitational potential of an approaching mass


What's exactly the new definition of kilogram, second and meter?

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


Why is hubble time the age of the universe?

Estimating age of the universe by Hubble's law?


Could it be that at the big bang equal amounts of matter and antimatter were created, but the antimatter got stuck in black holes?

Could the universe's antimatter be hiding in black holes?


Exceeding the speed of light in view of special theory of relativity

Why can't we surpass the speed of light?


When electrons move at high speeds, why is their mass LARGER than their rest mass? Why isn't it the opposite?

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


What equation could you use to model the shape of a thread when held at 2 ends?

What is the equation for a string fixed at both ends without simplifying assumptions?


Why is the $dx$ right next to the integral sign in QFT literature?


What is the origin of the Dirac delta term in the dipole electric field?


Do photons exist at all possible wavelengths?

How many possible electromagnetic wavelengths are possible?


Total angular momentum operator on $|m\rangle$ and $|m-1\rangle$ results in different eigenvalue

What is wrong with this deduction to show that within a multiplet different state has different square angular momentum?


Will magnifying light make it more powerful?

Besides the 2nd law of thermodynamics, what laws of optics prevent the temperature of the focal point of lens from being hotter than the light source?


Why is the electric field between two conducting parallel plates not double what it actually is?

Field between the plates of a parallel plate capacitor using Gauss's Law


Wave equation: $y=A \sin(\omega t-kx)$ or $y=A\sin(kx-\omega t)$?


Thomson's Plum Pudding and Rutherford's scattering

How did Rutherford's gold foil disprove the plum pudding model?


Can a star visually look like a black hole?

Black hole gravity vs parent star gravity


How does electricity travel near the speed of light if electrons drift at a snail pace?

Why the electric bulb turns on almost instantly when the switch is closed?


If an object with more mass experiences a greater gravitational force, why don't more massive objects fall faster?

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


Better Entanglement Explanation Required

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


Do gravitational waves violate the information paradox?

Did merging Black Holes in GW150914 give up entropy and information to the gravitational waves, since they lost 3 solar masses?


Work done by frictional force when rolling without slipping

How can friction do no work in case of pure rolling?


Inverse proportional to cosmological scale factor

Why is scale factor inversely proprotional to temperature?


Why does entropy of an ideal gas break the third law of thermodynamics?

Entropy of an ideal gas in $T\to 0$ limit


Difference between electron, muon and tau neutrinos

What is difference between the different 'flavours' of neutrinos?


Rotational mechanics collision problem of a rod and body


What qualifies as a quantum theory and why are we seeking a quantum theory of gravity?

Quantum made easy: so what *is* quantum mechanics all about?


Is the work-energy theorem only valid for conservative forces?

Validity of work-energy theorem in presence of non-conservative forces?


Spacetime as an independent yet interacting frame of reference for QM. Looking.for papers

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


As our velocity changes shouldn't the span of time taken change


Capacitance and introduction of conducting slab

What will happen if a conductor is introduced instead of a dielectric medium in parallel plate capacitor?


How do two waves after approaching and neutralising each other give birth to two waves the very next moment?

Why does destructive interference not stop a wave?


Have all Noether Charges been enumerated?

Is there a systematic way to obtain all conserved quantities of a system?


What happens at the interference of infrared and ultraviolet rays?

Why are light rays able to cross each other?


Is 3 Dissonant sounds considered as Beat Frequency or would it be a different type dissonance?


Where does the light of the fire come from?


How does a black hole have a magnetic field?

Do magnetic fields exist beyond the gravity of a black hole?


Is there any formula for strong and weak nuclear force?

Do strong and weak interactions have classical force fields as their limits?


Why do gamma ray and x-ray photons which have significantly higher energy travel at the same speed as photons of visible light?

Why does speed of light have to be constant?


Blackbody emission spectrum vs Boltzmann distribution

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


Looking for a self-contained book on QFT

What is a complete book for introductory quantum field theory?


Constant Internal energy of universe and its original source


Reconstruction of "wavefunction" phases from $|\psi(x)|$ and $|\tilde \psi(p)|$


What is the proof that a force applied on a rigid body will cause it to rotate around its center of mass?


Would there be any gravity inside a hollow planet made of a spherical shell of basalt crust?

Gravitational field intensity inside a hollow sphere


RFC on I-live-inside-a-massive-sphere Paradox


Electric Current in Classical Electrodynamics derived as Noether current

Noether's first theorem and classical proof of electric charge conservation


How to compute the constraint force of a rod falling on a table?


How can centripetal acceleration change the speed?

How can tangential acceleration from a radial force be explained?


Twin Paradox Explanation via Spacetime diagrams

What is the proper way to explain the twin paradox?


Recommendations for good Newtonian mechanics and kinematics books


Can matter be described as the result of the curvature of space, instead of vice versa?


Do I get shells, subshells, and orbitals right?

What do atomic orbitals represent in quantum mechanics?


How does friction allow bodies to rotate on merry go round?

Why does friction play the role of centripetal force during the turning of a car?


Why is there an extra $Z_3$ in Ward-Takahashi identity?

Ward identity derived from global symmetry and SDE, different from that derived from gauge symmetry?


Does special relativity imply that I can reach a star 100 light years away in less than 100 years?

How long would it take me to travel to a distant star?


Are the photons that we detect with our eyes virtual?

Can virtual particles be thought of as off-shell Fourier components of a field?


Why is it that when you wear polarized sunglasses, objects in the center of field-of-view are not obscured, but reflected lights have less intensity

Why do polarized sunglasses remove (most) reflections on car windows?


Noether's theorem with Newtons's approach

Elementary argument for conservation laws from symmetries *without* using the Lagrangian formalism


Why doesn't the frequency of light change during refraction?


How does the fabric of space-time bends?

How is gravity proportional to space-time curvature in the rubber-sheet analogy?


A simple explanation of the Born rule (v.2)?


Solving a Casimir configuration, the U - bracket


Electromagnetic waves highest frequency and beyond?

What happens when the frequency of A.C becomes infinite?


How to derive "a blob of water in space becomes a sphere" analytically?

Is it possible to prove that planets should be approximately spherical using the calculus of variations?


Frequency and wavelength of thermal radiation

The strange thing about the maximum in Planck's law


Is there a way to capture heat from the air? (and potentially store it?)

Why we won't extract heat from air temperature?


Calculating a matrix element, $\langle x|p\rangle$?

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


If an object falling at terminal velocity is pushed sideways, does it slow down vertically?

Will a bullet dropped and a bullet fired from a gun horizontally REALLY hit the ground at the same time when air drag is taken into account?


How do I derive the formula for radial acceleration when there is no uniform circular motion?

Proof of centripetal acceleration formula ($a_c = v^2/r$) for non-uniform circular motion


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


According to the Copenhagen Interpretation what does superposition mean?


Proton and Antiproton decaying into positive and negative pions

A proton and antiproton annihilate at rest into pions


What work is done by the wall when a ball hits it?


Trajectory of a projectile in 3d coordinate knowing the angle, the target position and with possible height offset

Solving for initial velocity required to launch a projectile to a given destination at a different height


How is Newtonian Mechanics contradictory to Special Relativity at a certain parameter?

"Newtonian limit" property of special relativity


Why is flux through a closed surface not infinite?

Electric field line density : Theory vs Reality


General definition of symmetry in physics?


What do spacelike and timelike intervals represent?

What do spacelike, timelike and lightlike spacetime interval really mean?


In SR length contraction, does matter flatten because the space around it flattens or does the structure of the matter flatten?


Classifying all symmetries of a mechanical system

Is there a systematic way to obtain all conserved quantities of a system?


What is the exact mechanism of flow of electricity?


If I surrounded a black hole with gravitometers and observed the gravitational field as mass passed the event horizon, what would I observe?

At what moment will matter falling into a black hole affect its size?


Does the existence of graviton contradict gravity being spacetime curvature?

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


Doesn't the Bohr's atomic model violate Maxwell's theory of electromagnetism?

Bohr's model of an atom doesn't seem to have overcome the drawback of Rutherford's model


Derivation of formula for electric field strength

Why is the electric field is the negative gradient of potential energy function?


Electromagnetic waves phase shifting needed?


Why is "degeneracy pressure" not considered a force?

Nature of the quantum degeneracy pressure


Limits of the Universe: how can be sure about the size of unobservable Universe?

How do we know the size of the universe?


How can we see through the matter like glass


Find the Hamiltonian given $\dot p$ and $\dot q$


Why is the work done by a rocket engine greater at higher speeds?


Particle travel time in the double-slit experiment?

Is it possible to determine the slit a photon went through in the double slit experiment by measuring its flight time?


Formula for molar specific heat capacity in polytropic process


Two objects moving relativistically towards each other

Time for two relativistic objects to meet


If $\psi$ acting on $a_+$ and $a_-$ operator just moves up and down the ladder, why is $[a_-, a_+] = 1$ and not 0?


Are there stars that wouldn't look white to the naked eye?


Rigorous underpinnings of infinitesimals in physics


Can somebody tell me what was the size of the universe and the expansion rate at the big bang?


If every object could give an equal and opposite force to what we apply then why do the objects exhibit translatory and rotational motion?

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


If an observer were to move toward the moon at a significant fraction of the speed of light, will its cross section appear a different size?

Approaching speed of light: why do objects appear further away in front of me?


If you were to be crossed by a wire the width of a single atom, would you still be split in half?

What happens if a metal wire that was one-atom in thickness was pulled across a finger?


How a moving electron gets deflected in a magnetic field in on direction and the positron gets deflected in the opposite direction?

In electromagnetism, why does nature prefer the right-hand rule over the left-hand rule?


What does it mean to make a sound twice as loud?

Why do we use decibels instead of just using intensity to measure how loud things are?


Can a charged particle interact with its its own electromagnetic field?

Influence of charged particle's own electric field on itself


Degrees of freedom for diatomic molecules

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


If a box is carried 2 flights of stairs to an attic, is more work done than opposed to go straight up with a ladder?


Could electrons with a certain wavelength pass through a hole, or chamber, smaller than their wavelength?

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


What would the collision of two photons look like?


How do we know that human eye reacts on frequency of visible light rather than on some other parameter?

What determines color -- wavelength or frequency?


Is work done by a person while walking negative?


Basic question about the necessity for Newtonian mechanics

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


Spectroscopic properties of hydrogen: H vs. H2


Why is there no friction at the top and bottom of loops?

Does friction always act opposite to the motion of the body?


What form of energy was the energy of the universe before the Big Bang?

Conservation law of energy and Big Bang?


Newton's third law of motion and frictional force

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


Is there any anti-hermitian operator in quantum mechanics?


Is the (electrostatic) interaction energy always positive, or can it be negative?

How can we have negative work in electrostatics, if $W=(\epsilon_0/2)\int\! E^2\ \mathrm{d}\tau$?


Is the second law of thermodynamics even a law?

Is a spontaneous decrease in entropy *impossible* or just extremely unlikely?


Are there any effect of Sun to the tide?


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


Could Black Hole be formed with the center of some stars?


Why doesn't a star's core cool down when it expands as a red giant?


Is it theoretically possible that electrons are made up of quarks just like protons and neutrons?

Why do physicists think that the electron is an elementary particle?


How does one divide by a vector when calculating pressure?


Behavior of a source with internal resistance connected in parallel with a resistor $R$


How to calculate the gravitational force of a black hole outside event horizon at a given distance $r$?

What is the weight equation through general relativity?


Rindler metric and equivalance principle

Applying the principle of equivalence to an accelerated frame


Does warping of space under relativity suggest displacement

Better explanation of the common general relativity illustration (stretched sheet of fabric)


Why do blackbodies emit all frequencies of light?

What causes a black-body radiation curve to be continuous?


Experiment of an accelerated charge’s radiation in General Relativity

Can the question of a gravitationally accelerated charge radiation be tested experimentally?


Zero radiation resistance for constant acceleration?

Does a constantly accelerating charged particle emit EM radiation or not?


Why are the two outer charge densities on a system of parallel charged plates identical?


Is there an upper bound on acceleration?

Is there a maximum possible acceleration?


Global uniqueness and determinism in classical mechanics

What situations in classical physics are non-deterministic?


Where do we observe the effect of quantum-level repulsion and what is its origin?

Why is the second order perturbative correction to the ground state energy always down?


Why isn't acceleration always zero whenever velocity is zero, such as the moment a ball bounces off a wall?

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


Why is pressure-volume work calculated from the external pressure if the work is done by the gas?


What is the formal definition of energy in physics?


How did Newton use his theory without the value of $G$?

Did Newton estimate the gravitational constant $G$?


Why are time dilation and length contraction needed to fix time?


What's the physical meaning of the imaginary component of impedance?


Destructive interference in vacuum (energy conservation)

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


Why optical phonons are called "optical"?


How is depth perception linked with the separation between our eyes?


Hypothetical maximum energy of a single photon

Are there any theoretical limits on the energy of a photon?


Is there a proper explanation for WHY, not how, gravity causes objects to accelerate from a standstill?

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


Bohr's model of an atom doesn't seem to have overcome the drawback of Rutherford's model


Driving force and mean of a particle wave function

"Reality" of EM waves vs. wavefunction of individual photons - why not treat the wave function as equally "Real"?


Why did the Lockheed Martin compact fusion reactor failed?


How can I get an equation of trajectory of a particle mathematically for circular motion?

What will be the trajectory of the given motion


A changing magnetic field passes through a wire loop but the loop itself is not in the field. Is an EMF induced in the loop?

Simple explanation to the induction from the slowly changing $\vec B$ of a solenoid in the region of $0$ magnetic field


Where does the half of Potential energy go?

If string is stretched just by weight, where does the gravitational potential energy goes if only half is converted to elastic potential energy?


Does the speed of light in different mediums affect the lorentz transformation?


What does the Heisenberg principle actually mean?

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


Can relative permittivity be less than 1?


Why are so many energies represented by $\frac{1}{2} ab^2$?

Coincidence, purposeful definition, or something else in formulas for energy


The Lagrangian and inertial reference frames

Do we need inertial frames in Lagrangian mechanics?


When space expands where do the energy of the gravitational wave dissipate to?

Redshifting of Light and the expansion of the universe


Why is it commonly said Angular momentum for ground state is zero (for system with rotation invariant potential)?

Why doesn't the uncertainty principle contradict the existence of definite-angular momentum states?


What is the heat needed for an isothermal expansion of gas and why do physics and chemistry yield different answers?


What is the $d/dt$ in the Schrödinger equation?


How do we construct the matrix representation for three Grassmann numbers?

How do you find a particular representation for Grassmann numbers?


Where do the bipolar jets of black holes come from?


Given that 1D space $\mathbb{R}$ and 3D space $\mathbb{R}^3$ are in bijection, why do we describe our physical world as 3D?

Is 3+1 spacetime as privileged as is claimed?


Free Form Diagram of one block on top of another block

Why do we treat weight as acting on the object?


In a simple battery + resistor circuit, what form of energy is lost from the electrons upon exiting the resistor?


Rigorous underpinnings of infinitesimals in physics


The solution to the differential equation, equation 1.7.28 in Sakurai (2nd Edition)

Normalization of the overlap $\langle x'|p'\rangle$


Effective Refractive Index: Where does this formula come from?


General Relativity and antimatter: Would antigravity of antimatter really disprove GR?

Does antimatter curve spacetime in the opposite direction as matter?


Conservation of energy and Doppler effect?


How do you find the average of relative uncertainties?

How do you find the uncertainty of a weighted average?


Please help me relate two different definitions of the stress-energy tensor


Why Electric field is same at every distance from the sheet inspite of inverse square law?

Why is electric field of an infinite plate constant at all points?


Dirac delta function and volume charge density


Is the Pauli Exclusion Principle the Cause of Normal Force?

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


How to prove that a sphere has the minimum gravitational potential energy for a given volume of uniformly dense material?

Is it possible to prove that planets should be approximately spherical using the calculus of variations?


Is the potential at each point on a circuit same?

How electric currents can flow between 2 points at the same potential?


What would happen if I rotated an extremely long stick?

Extended Rigid Bodies in Special Relativity


Benefits and Drawbacks of Swapping Associations of Positivity and Negativity of the Proton and Electron


Is there any connection between special relativity and general relativity?

What is the connection between special and general relativity?


Intuitive explanation for why reflected waves change phase by $π$?

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


Is there a deep reason why a non-relativistic Lagrangian does not have higher order derivatives?

Why are there only derivatives to the first order in the Lagrangian?


A photon travels in a vacuum from A to B to C. From the point of view of the photon, are A, B, and C at the same location in space and time?

How does a photon experience space and time?


If space is continuous, then frequency and photon energy too?

Is the electromagnetic spectrum discrete?


Why is time different between different inertial observers?


What do angle have to do with waves? Why do we use trigonometric functions to model waves?

Why are cosine and sine functions used when representing a signal or a wave?


Where does the mass of a proton come from?

Why does the quarks binding energy add mass to nucleons instead of reducing it?


Electric Field of an Infinite Sheet Using Gauss's Law in Differential Form $\nabla\cdot\text{E}=\frac{\rho}{\epsilon_0}$

Electric field for point charge in a smoothly-varying dielectric?


How does the electric field of a Reissner-Nordstrom black hole exist outside its event horizon if nothing can escape the event horizon?

Detection of the Electric Charge of a Black Hole


Why does two objects with different weights fall at the same time, taking air resistance to be negligible?

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


Is there a way to derive the Gauss-Faraday Law in the Covariant formulation of classical electromagnetism from the Lagrangian density?

How to derive Maxwell's equations from the electromagnetic Lagrangian?


Why does a stationary object start moving if there is no force acting on it in general relativity?

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


If electron moved in a definite orbit, would that violate Heisenberg uncertainty principle?

Does electron orbital theory contradict the Heisenberg uncertainty principle?


Time and the incompatibility of General Relativity and Quantum Mechanics

Why is there a “problem of time” in Quantum Gravity?


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


Why is work done equal to force×displacement?

What is behind the definitions of work and energy?


Question about understanding the behavior of the universe

Is the universe fundamentally deterministic?


If an object is free falling under gravity, then where is the pseudo force applied?

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


Speed of light in a gravitational field?


What is the direction of the force of buoyancy at the bottom of the liquid?

Does buoyant force vanish if there is no liquid below an object?


How "smooth" is the evolution of the universe?


What's the Difference Between Work and Energy?


Is energy always a constant when the momentum is constant?

Does momentum change when Kinetic energy changes?


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


Deriving approximate wave function of virtual photons in a simplified model of momentum transfer

Force carrier particle exchanges and attraction


What percentage of the mass/energy of the universe is in the form of electromagnetic waves?

Where is radiation density in the Planck 2013 results?


What keeps a swinging rubber ball in a horizontal circle above head from falling?

Ball swung in a horizontal circle, can the string ever by exactly horizontal to the ground?


How can I predict if water will stick to the outside wall of a container when pouring at a certain angle?

Why does water pouring from a glass sometimes travel down the side of the glass?


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


NASA's "Impossible" Space Engine, Take Two

What are the proposed theoretical explanations for the EmDrive?


How much photon energy has already been destroyed?

Conservation of Energy vs Expansion of Space


Transformation between a dynamical system to a Hamiltonian system

When can an autonomous system be written using a Hamiltonian?


Why can't we fly aeroplane or shuttle directly into the space (beyond 100 km height above Earth's surface)?

Why do spacecrafts take off with rockets instead of just ascending like an aircraft until they reach space?


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


Higher energy of outer orbitals around nucleus

Why does an electron shell further away from nucleus has higher energy level?


Why $g$-force increase with radius and centrifugal force decreases?

How is centripetal force related to radius?


Why is there no constant factor in the equation $E=mc^2$?

Why isn't it $E \approx 27.642 \times mc^2$?


Is Time a container of Space, or separate from Space?

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


Why do we neglect the hydrostatic pressure difference in a hydraulic lift?

Why don't we include $\rho g h$ in a hydraulic jack below?


What to know to start learning Quantum Mechanics

What's the standard "roadmap" to learning quantum physics?


How may the situation, when there is no inertia?


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


Book recommendation on Quantum Mechanics which is a bit mathematically aligned and gives good introduction to Hilbert Space for beginners

A book on quantum mechanics supported by the high-level mathematics


Where can I learn about the reflection/refraction of sound waves and acoustic impedance in a way similar to quantum tunnelling?

Which book would you recommend for a dummy wanting to start studying acoustics, out of interest?


Recommended books for introduction to Quantum Mechanics for students who are mathematically aligned


Why do the degrees of freedom of a density operator not match up with the degrees of freedom of a state vector?

Why does the space of pure qudit states have dimension $2(D-1)$, rather than $D^2-2$?


Intuition for Quantum Mechanics (if it exist!)

What is a wave function in simple language?


Why do parallel plates create a unifrom field?

Why is electric field of an infinite plate constant at all points?


Why X-ray and radio waves can penetrate walls but light can not?

How can wifi penetrate through walls when visible light can't?


Time between two observer in special relativity


Is there a difference between a field and a function?


Current and voltage - Incompatibility between Ohm's Law and Power Law!

Contradiction in Ohm's Law and relation $P=VI$


Symmetry in time dilation in special relativity


Where does electrostatic interaction come from?

Deriving the Coulomb force equation from the idea of photon exchange?


Equilibrium of two suspended charge particles

Why are approaching discharging initially charged pith balls almost at equilibrium?


Modern references for continuum mechanics


Book recommendations on General Relativity


Why can two particles in a box have different quantum numbers and still be indistinguishable?


What is the definition of a timelike and spacelike singularity?


How the speed of light remains stable inside a transparent material?

What is the mechanism behind the slowdown of light/photons in a transparent medium?


How does an expanding universe and a constant-density vacuum energy not violate energy conservation?

How is dark energy consistent with conservation of mass and energy?


Why are many variable probability distribution described by a Tensor product?

Should it be obvious that independent quantum states are composed by taking the tensor product?


Does the Hamilton-Jacobi equation imply that there are always $N$ conserved quantities for any system with $N$ degrees of freedom?


D'Alembert's principle derivation in Goldstein's Classical Mechanics book

Why does cancellation of dots $\frac{\partial \dot{\mathbf{r}}_i}{\partial \dot{q}_j} = \frac{\partial \mathbf{r}_i}{\partial q_j}$ work?


Does effect of force travel faster than light?

Extended Rigid Bodies in Special Relativity


Books or papers on statistical mechanics, given information theory background?

Reference for statistical mechanics from information theoretic view


What Ron Mallett doing for time machine here?

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


The direction of friction in rolling without slipping

Force of friction in rolling without slipping


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


According to newton's third law "for every force there is an equal and opposite reaction" then explain how our our arms move?

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


Beams of different colors do not interfere with each other

Why don't waves with different wavelengths interfere with each other in white-light?


Definition of Generating Function and Momentum

Motivating the ansatz for the infinitesimal translation operator


Does every point in a system has equals moment (Torque)?

Is torque independent of choice of the point of rotation?


Is there jerk on Uniform Circular Motion?


If we can live with classical EM field in atomic physics, why can't we live life with a classical theory of gravity?

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


Why is the energy function not always equal to total energy?

When is the Hamiltonian of a system not equal to its total energy?


Where does half of the work done in charging a capacitor is dissipated?

What happens to half of the energy in a circuit with a capacitor?


Why can only the Higgs particle have a non-zero expected value in a vacuum?

Why cannot fermions have non-zero vacuum expectation value?


Is quantum mechanics just a mathematical trick?

Is the wave-particle duality a real duality?


Generalising a Dirac Delta function formula in General Relativity


How do we know that superposition exists?

Has it been practically proven that quantum superposition exists ? If yes, how does it even work?


Which is the Best Free Physics Simulator that can simulate the dropping of a ball?

Simulation software to solve high school level mechanics problems


Why are drag and kinetic energy proportional to velocity squared?

Why does kinetic energy increase quadratically, not linearly, with speed?


How to convince myself that capacitance cannot be a function of voltage?


Do two specks of antimatter experience antigravity between each other?

Has the gravitational interaction of antimatter ever been examined experimentally?


Does the uncertainty principle say that conservation of momentum is violated in quantum mechanics?

Can conservation of momentum be violated?


Is it possible to make a tiny approximation in the equations of General Relativity so that they collapse to Newton's law of gravity?

How can we recover the Newtonian gravitational potential from the metric of general relativity?


Analytic solution for angle of minimum deviation?


Doesn't this experiment signify that inertial frames are not equivalent?


Differences between gamma rays and X-rays

What's the difference between Hard X-rays and Gamma-rays?


Proof that derives Newton's law of gravity

How did Newton discover the universal law of gravitation?


Constants of motion vs. integrals of motion vs. first integrals


Why do atoms oscillate at absolute zero?


Why does an oscillating mass does not produce gravitational waves (in contrast with an oscillating electric charge)?

Why there is no dipole gravitational wave?


Difficulty understanding why acceleration of free fall is lower at the equator than the poles

Why is Earth's gravity stronger at the poles?


Is there such a thing as negative dimensions?

Could negative dimension ever make sense?


Estimate Calories Burned from Arbitrary Limb and Body Movements

Estimate Calories Burned from Arbitrary Limb Movement


Are matrices and second rank tensors the same thing?


Could someone explain the muon $g-2$ experiment problem?


Electromagnetism, linearity and Feynman diagrams

Non-linearity and self-coupling of gravity


Book recommendations for fluid dynamics self-study


Why does the bullet have greater KE than the rifle?

Why does shooting a handgun accelerate a bullet to deadly speed without injuring the gun user's hand?


If spacetime is expanding, shouldn't lengths expand at an equal rate?

Why does space expansion not expand matter?


Interpretation of measurements and Eigenstates for continuous variables

Are eigenstates of the position operator continuous?


Events that can't be simultaneous to any observer?

Is there always a frame in which spatially separated events are simultaneous?


A thought experiment to prove that Newtonian gravity is incomplete

Are moving objects producing stronger gravity fields?


Is there any true inertial reference frame in the universe?


Can you help me resolve this paradox for a geodesic orbit? Does it maximize proper time to sit still rather than orbit for 1 year?

Is the orbit in Schwarzshild metric a path with maximal proper time?


Flow in vertical pipe and Bernoulli's equation

Is equation of continuity valid, while dealing with vertical pipes?


Can you have quantum gravity without gravitons?

Why quantising gravity necessarily give us gravitons?


What is actually spinning in quantum spin?

What is spin as it relates to subatomic particles?


Is there a minimization principle for Hamiltonian?

Finding a "Principle of Least Action" equivalent statement for Hamiltonian Mechanics


Can the double pendulum equations not be derived solely using Newtonian Mechanics (Newton's Laws of Motion)?


Why do Solar Systems form in a disc shape?

Why are our planets in the solar system all on the same disc/plane/layer?


Will everything eventually be a single black hole?


Why I think tension should be twice the force in a tug of war


What are electrons holes and how they differ from free electrons?

What are "electron holes" in semiconductors?


The problem of time in quantum cosmology

Why is there a “problem of time” in Quantum Gravity?


Meaning of a product of two physical units


Can we say normal stress and pressure are the same?


Recommended books for advanced undergraduate electrodynamics


Interesting twist to the classic Twin Astronaut paradox: the astronaut twin moves against Earth's orbit and waits hovering in space

Can you help me resolve this paradox for a geodesic orbit? Does it maximize proper time to sit still rather than orbit for 1 year?


Where did the kinetic energy formula come from?

Why does kinetic energy increase quadratically, not linearly, with speed?


Why does the universe exhibit three large-scale spatial dimensions?


Can expanding space stretch the wavelength of GWs?


Does bulk translational motion factor into average kinetic energy as it relates to temperature

How does temperature relate to the kinetic energy of molecules?


Why do the two slits of a double slit experiment not make light coherent and create an interference pattern if monochromatic light is passed through?

Is coherent light required for interference in Young's double slit experiment?


If in space with no opposing force,will a body of 1kg pushed with 1N force keep on accelerating 1m/sec every second? When will it stop accelerating?

Will something accelerate forever if a constant force is applied to it on a frictionless surface? If so how?


What is the volume inside the event horizon of a black hole?

Do black holes have infinite areas and volumes?


WKB near turning point by means of complex integration (Landau & Lifshitz, Quantum Mechanics)

Landau & Lifshitz's Approach (contour method) on the WKB connection formulas


Does the apple fall towards the earth or does the earth move up to the apple?

Do the Earth and I apply the same gravitational force on each other in GR?


Light emission from the vicinity of a black hole

How can Quasars emit anything if they're black holes?


Shouldn't we also see our galaxy clusters in that ring just beyond the shadow of M87?


Is the M87 black hole really a black hole?

How long does it take for a black hole to form for an external observer?


Question About Gravity vs. Earth’s Rotation

Earth moves how much under my feet when I jump?


Basic Question on Black Holes and the Potential Loss of Conservation of Energy/Mass

Is energy conserved when things fall into a black hole?


Does the state of curl of the $E$-Field at a point adjust itself instantaneously as soon as $B$ begins changing at a fixed rate, or is there delay?

How quickly is the desired state of curl of the Electric Field around a point achieved where a Magnetic Field Vector has just begun changing?


Does a photon instantaneously gain $c$ speed when emitted from an electron?


How do rocket engines work in EMPTY space?

What is a rocket engine thrusting against in space?


In M-Theory are membranes excited states of a field?


What actually led Feynman to the Path Integral?

Dirac's remark that inspired Feynman when formulating path integral


Pushing a long stick into the event horizon

Thought Experiment - Poking a stick across a Black Hole's Event Horizon


Why was the imaging of M87 black hole easier than imaging the Milky way's Sagittarius A*?

Why was M87 targeted for the Event Horizon Telescope instead of Sagittarius A*?


How do the Planets and Sun get their initial spin?


Independence of position and velocity vector

Why does cancellation of dots $\frac{\partial \dot{\mathbf{r}}_i}{\partial \dot{q}_j} = \frac{\partial \mathbf{r}_i}{\partial q_j}$ work?


Would not the oscillation of light slow down the wave?

Photons are faster than the speed of light because they travel in transversal waves?


Why is $R\cos{a} = mg$ in circular motion compared and not $R = mg\cos{a}$?


In $E=hf$, can $f$ assume any positive value? (Beginner)

Is the electromagnetic spectrum discrete?


Hamiltonian formulation of the geodesic equation

Constraints of relativistic point particle in Hamiltonian mechanics


Why use $\ln$ in definition of pseudorapidity?

Why is pseudorapidity defined as $-\log \tan \theta/2$


Why is the laboratory frame energy always greater than the center of mass frame energy for collisions?

Why is the laboratory frame energy always greater than the center of mass frame energy?


Does a circle become bigger or smaller when rotating?

Understanding the "$\pi$" of a rotating disk


Is there a concept of velocity at quantum level?

Why we dont have "direct" velocity operator just as $p$? ( as use $p$ space not $v$? ) in quantum mechanics?


Why do we prefer to write free energies as functions of particular state variables?

Understanding "natural variables" of the thermodynamic potentials using the example of the ideal gas


Reason for inertia of motion of Earth orbiting the Sun


Driving car with (almost) the speed of the light and switch the headlights on


Why diodes can be used to create a current-independent voltage drop?


The power of an EM wave is proportional to the amplitude (squared). But also the frequency?


What is negative energy as used by Dirac to explain pair production?

What was missing in Dirac's argument to come up with the modern interpretation of the positron?


Is it a coincidence that quarks have exactly -1/3 or 2/3 the electron's charge?

Why do electron and proton have the same but opposite electric charge?


Why is it important that physics consists of unitary phenomena?


What constitutes measuring in the double slit experiment?

What is the quantum mechanical definition of a measurement?


Will the electron affected by another electron via Coulomb's force affect this electron instantly?


Are physical probabilities also quantized?


Explain Lenz Law with Conservation of Energy


Could light find itself in orbit around an object?


Can amateurs use the retroreflector on the moon?


Can Heat Transfer occur between two bodies with the same temperature but different states only through Latent Heat Transfer?


What will happen if the refractive index of lens is less than unity?

How can the refractive index be below 1 in a dielectric?


the type of movement in electron jump between levels?


What would happen to a person's body if they entered a black hole?

Thought experiment - would you notice if you fell into a black hole?


How did Newton explain the effect we now call Newton's Rings?

What was Newton's own explanation of Newton's rings?


Size of the universe as a function of time

How can something finite become infinite?


How does the Sun provide enough energy to fuse protons?


Why do matter behind event horizon exerts gravitational pull?


Could traffic acceleration/deceleration change the rotation of Earth?

Do mankind and manmade activities/constructions have any effect on the rotation of the Earth?


Why does inelastic collision obey the conservation of momentum?

Why is momentum conserved in inelastic collisions? How is it related to momentum-impulse theory?


Are both kinetic energy and momentum conserved when 2 objects undergo a collision?

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


What is the mass of Photon or Light Particle?


Is there a way to derive Principle of Least Action from Newton's laws instead of other ways around?

Is there a proof from the first principle that the Lagrangian L = T - V?


Why is the set of physically acceptable solutions to the time-independent Schrodinger equation discrete?

Discreteness of set of energy eigenvalues


If extra dimensions are out there, why don't/can't we see them?

Extra Dimensions (in String Theory) - What does it mean?


Does the principle of conservation of momentum really imply Newton's third law? ("Classical Mechanics" by John Taylor)

Does conservation of momentum really imply Newton's third law?


Would looking out from inside or near a black hole be unimaginably bright?

What will the universe look like for anyone falling into a black hole?


Physical interpretation of complex numbers

Can one do the maths of physics without using $\sqrt{-1}$?


Why does water fall sort of helically from a cup?


Is the universe fundamentally deterministic?


How can one motivate the relativistic momentum?


Do physicists understand why time slows down the faster the velocity of an object?


Can we see a real image with naked eyes?


In layman terms: Why can't Quantum Entanglement be used to achieve FTL Communication?

Quantum entanglement as practical method of superluminal communication


If I kept a body in a groove on a frictionless circular table, and rotate the table with a constant angular velocity, what will happen to the block?

Is the force which throws a body on a rotating disk outwards centrifugal force?


Simple calculation on coordinate transformation of Lagrangian (Qualls' CFT lecture note)


Why is the wave of a sound in a tube reversed?

How can standing waves be produced in an open organ pipe if the ends are open?


Work done by a person climbing stairs, who or what does the work?

What is the correct way to estimate the work done by a climber?


How to differentiate between mass and weight?

What is the difference between weight and mass?


Rewriting the Lagrangian in terms of the constant(s) of motion doesn't work. Why? (spherical pendulum)

How can you solve this "paradox"? Central potential


How come photons have no mass if they have energy and $E=mc^2$?

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


What Is the logic and the intuition of the Heisenberg Uncertainty Principle based on? Is it Quantum Superposition or on the electromagnetic spectrum?

Can the Heisenberg Uncertainty Principle be explained intuitively?


How do you express conformal time $eta$ as a function of the scale factor $a$

What is the relationship between Cosmic Time and Scale Factor (or Redshift)?


Is there an intuitive explanation for Newton's Third Law?

Why does Newton's Third Law actually work?


I was solving a capacitor problem the other day and encountered a question on redistribution of charges

How can a capacitor discharge if there is no field outside?


Does the speed of light depend on mass density?

Does the optical density of a medium depend upon its mass density?


Why do some kind of black bands or lines appear when I'm just about to touch two fingers ?There is a second question too

Why do shadows from the sun join each other when near enough?


Why is quantum measurement not happening all the time?

Why aren't particles constantly "measured" by the whole universe?


Applying uncertainty principle to energy states

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


Gravitational light bending and refraction?

Gravitational lensing or cloud refraction?


Would a spinning particle in a spinning universe have spin?

Quantum spin in a rotating reference frame


Why does Joule's Law of Heating defined by $H=i^2R$ only?


Why is the mole/"amount of substance" a dimensional quantity?


Why does the conserved quantity generate the transformation in quantum mechanics?

Why does the classical Noether charge become the quantum symmetry generator?


Why doesn't a backward wave exist? (Huygens principle)

How does Huygens Principle incorporate the unidirectional property of a traveling wave?


Are only gauge bosons massless or all elementary particles (above the energy of symmetry breaking)?

Are there massless bosons at scales above electroweak scale?


Why is permeability of free space (in calculation of magnetic field) a non zero number?


If we can see only visual light then why we can't see other electromagnetic radiation as they also a type of light?


How does the melting ice cube in a glass of water doesn't change the water volume?

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


When a stick that has been twisted into a knot burns, what happens to the potential energy?

What happens to the potential energy of a compressed spring when it dissolves in acid?


Problem book in Quantum mechanics with emphasis on physical(ly relevant) problems


Why is the gravitational potential energy defined as negative?

Why gravitational potential is negative, as displacement and force are in the same direction?


The magnetic field of a magnetic monopole


What exactly is the meaning of length contraction?

What is the real meaning of length contraction?


What kind of matter are black holes made of?


Why light coming from distant stars is not discrete?

Photons from stars--how do they fill in such large angular distances?


How can we write relativistic momentum without length length contraction?

Why is the momentum of a particle $\gamma mv$?


Why does the black hole's matter ring in the image released on April 10th seem to lack blue/red shift?


Where does the inconsistency between QM and general relativity stem from?

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


What is the proper way to explain the twin paradox?


Why a musical instrument's string oscillates with many frequencies?

How is it possible that multiple overtones can exist at the same time?


What components would produce this polarization/waveplate demo?

Are these sunglass lenses linearly polarized or what?


how does a car move? and how do the brakes affect its velocity?


What is the source of the difficulty (within the variational approach framework) in the attempt to unify quantum mechanics with general relativity?


What is the practical Length of photons, in vacuum for example


Why Electric field inside the spherical shell is zero?


If you could bottle a photon would it have mass?

Explain how (or if) a box full of photons would weigh more due to massless photons


Why does the Earth not fall towards the Sun?

Why doesn't the Moon fall onto the Earth?


How is frictional force dependent on normal reaction?


Do neutrinos not couple to the Higgs field?


Which books or content should I prefer to understand particle physics operator and representations


Understanding angular velocity in spherical polar coordinates


Why is anti-neutrino produced along side with electron in beta minus decay?

Neutron decay and electron anti neutrino $n\to p + e + \bar{\nu}_e$


Do virtual images exist in the real world?


Why do people suspect antimatter falls upward?

Why would Antimatter behave differently via Gravity?


Book suggestion for quantum mechanics for a noob

What is a good introductory book on quantum mechanics?


Electrostatic force between charges placed in different medium

Electric force between charges in two different media


What is the minimum distance between an electron and a positron so that they do not annihilate?

How close does a particle-antiparticle pair need to be for annihilation to happen?


Finding instantaneous rotation and translation from multiple forces


Mechanism for a photon to impart momentum to an atom

How does one account for the momentum of an absorbed photon?


What is the real notion/feel of a tensor quantity?

How to understand the definition of vector and tensor?


GR. Einstein's 1911 Paper: On the Influence of Gravitation on the Propagation of Light


If Newton's third law is true, why can we sink in sand?


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


Why do we steer in the opposite direction while countersteering?


How does matter turn to energy at the atomic level?


Is there a higher-level reason why $\nabla\cdot(\hat{\bf r}/r^2) = 0$ in three dimensions but not two?

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


Why do we say there are four fundamental forces in the Standard Model (if gravity is included)?

Why are there only four fundamental interactions of nature?


Isn't magnetism governed by the inverse square law?

Why does magnetic force vary in proportion to the cube of the distance instead of the square?


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


Doubt regarding work done in separating capacitor plates

Energy changes due increasing plate separation of unconnected charged capacitor


Heisenberg choice of the observables and different outcomes

How do we know a quantum state isn't just an unknown classical state?


How is mass accounted for when a particle is in a superposition?

Is mass an observable in Quantum Mechanics?


Example in which light takes the path of maximum optical length

Examples in which the light maximizes the optical path length


Chosing a reference frame in which the Earth is at rest and doesn't rotate


What shape of track minimizes the time a ball takes between start and stop points of equal height?


Relatively simple problem in special relativity physics

Dancing twins, one travelling in a rocket ship, looking through telescopes at each other


How much does NASCAR affect the rotation of the Earth?

Do mankind and manmade activities/constructions have any effect on the rotation of the Earth?


Why is velocity mathematically describes as a division?


Formula for combining relative uncertainties

Why is propagation of uncertainties quadratic rather than linear?


Why is a conservative force defined as the negative gradient of a potential?


Is it possible to calculate the average value of $x^{2}p^{2}$ for an infinite square well?

Deriving a QM expectation value for a square of momentum $\langle p^2 \rangle$


The light signal path through the light clock

Why does a light beam in a moving light clock follows a V shaped path?


Why is time-reversal represented by an antilinear and antiunitary operator?

Why exactly does the time-reversal operator need to be anti-linear?


is this the reason why current doesn't flow over a resistance if there is another path without resistance?

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


How can I read off the fact that gravity is associated with spin-2 particles from the Einstein-Hilbert action?


Why when light enters to another medium it changes its direction?

Why does change in speed of a wave make it refract?


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


How to learn Gravitation after 20 years?


Frequency of the sound when blowing in a bottle


Is it possible to travel at the speed of light?

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


How to calculate incident solar energy on earth in a given day with a spectral filter


Why do planets move in elliptical orbits around the sun?

How is the equation of motion on an ellipse derived?


Proof of an accelerated expansion of the universe

What is the evidence that dark energy exists? (as of 2020)


Effect of Gate Voltage on conductivity - MOSFET


Proton: 2 up, 1 down quark, Neutron: 2 down, 1 up, how can Neutron: proton + electron?


Is there a Noether's theorem in quantum mechanics in the path integral formalism?

Is there a formulation of Noether’s theorem for the path integral formalism?


Why identify the Lagrangian as kinetic energy minus potential energy?

Is there a proof from the first principle that the Lagrangian L = T - V?


How to know if a measure is Lorentz invariant?


Can gravitational waves escape a black hole?

Can we detect gravitational waves generated from inside the event horizon of a black hole?


Speed of one frame with respect to another in special relativity

Why is the relative velocity of B with respect to A negative of the relative velocity of A with respect to B?


Least action principle and its quantum mechanical view

Why is the contribution of a path in Feynmans path integral formalism $\sim e^{(i/\hbar)S[x(t)]}$?


Should the eigenkets be weighted in $|P\rangle = \sum\limits_{r}|\xi^r\rangle$?


Thermodynamics and the state postulate: should it be a Fourth Law?


How am I able to stand up and walk down the aisle of a flying passenger jet?


Why is the covariant derivative of the stress-energy-momentum tensor zero?

Reason for vanishing of the covariant derivative of energy-momentum tensor of matter in general relativity


Is a superconductor really a super conductor?


Covariance of Euler-Lagrange equations under change of generalized coordinates


Is energy conserved during the expansion of the universe?

Is the law of conservation of energy still valid?


Relativity question. How to conceive two star ships receding from each other, each going near light speed


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


Photon Interference in a double slit experiment

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


Angular momentum eigenfunctions and commutators

Eigenspaces of angular momentum operator and its square (Casimir operator)


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


Is the universe fundamentally deterministic?


How can Earth accelerate toward US and China with no expanding?

Why doesn't planet Earth expand if I accelerate upwards when standing on its surface?


For basic understanding what is is constant of motion is constant of motion refers to constant motion?

Constants of motion vs. integrals of motion vs. first integrals


If the Sun's temperature is around 5000K to 6000K which means it is a yellow star, why does it appear white in space?

Why doesn't the Sun appear green to our eyes?


Work and energy: law of conservation of energy?

Is the total energy of the universe zero?


How much energy is in the Universe as photons?

How much light is there in space and how heavy is it?


Why is the cross-product of two vectors perpendicular to that plane?

Why is the direction of cross products of two vectors perpendicular to the plane?


Can we handle the wave function as if it was a real valued function?

When Eigenfunctions/Wavefunctions are real?


What is the equation for the refracted vector when using Snell's Law with 3D vectors?


Functional derivative simplification for effective action derivation

I want to understand a trick in the derivation of the Schwinger-Dyson equations


Why the extraterrestrial solar spectrum is higher than blackbody spectrum?

How can it be that the sun emits more than a black body?


Which of the four fundamental forces is responsible for covalent bonds?

Covalent bonds are EM (electrostatic/electronegativity) or not?


Calculate Lagrange Points between Sun and Earth


Two rotating discs with same angular momentum when brought in contact completely stop. Why is the angular momentum not conserved in this case?


How do we measure Time period of a SHM without mathematically calculating ? Consecutive passage through mean position or extreme postion?

Better method to measure the time period of a pendulum


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


Why is "Gravity as a result of space-time curvature" not accepted as a fact?

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


How does the whole universe agree on the laws of physics?

Do the laws of physics work everywhere in the universe?


Is time a byproduct of mass in some sense?

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


Is it possible that antimatter has positive inertial mass but negative gravitational mass?

Has the gravitational interaction of antimatter ever been examined experimentally?


Regarding Goldstein's claim that $\mathbf{F} = \dot{\mathbf{p}}$


Is electron revolving clockwise or anticlockwise around nucleus?

Quantum mechanical picture of "electrons orbiting the nucleus"


Angular momentum conservation - elliptical motion

Conservation of angular momentum in a planetary system


What is the reasoning behind the rules for compounding errors?

Why is propagation of uncertainties quadratic rather than linear?


Energy neither created nor destroyed. Then where energy comes from?

Conservation law of energy and Big Bang?


What is the difference between invariance and covariance?

Definitions and usage of Covariant, Form-invariant & Invariant?


What systems can the Principle of Least Action be applied?

How do I show that there exists variational/action principle for a given classical system?


Are we really moving at the speed of light in the time dimension?

Why are objects at rest in motion through spacetime at the speed of light?


Difference between field and wavefunction


What is the energy density of a 10 solar mass black hole as if the mass is distributed throughout the volume of the event horizon.?

What is exactly the density of a black hole and how can it be calculated?


Minkowski diagram and length contraction


Can Ligo tell a blackhole and neutron star of same mass throughout the inspiral?

How do LIGO and Virgo know that a gravitational wave has its origin in a neutron star or a black hole?


How does an outcome of photon measurement 1 affect Photon 2 in quantum entanglement?

Understanding quantum entanglement.. help me validate this analogy!


Conservation of energy when ball rebounds

Contradiction between law of conservation of energy and law of conservation of momentum?


Why are gravitational mass equal to the mass in Newton's second law

Is there a fundamental reason why gravitational mass is the same as inertial mass?


Why does reduced mass help when talking about two body problems?


Is it possible for a charged particle to have no spin?

Why are there no elementary charged, spin-zero particles?


Why usually we don't have a linear term in the potential?


Energy conservation when light reflects from mirror

Does a reflection still transfer momentum to an mirror?


Changing the Half-Life of Radioactive Substances


Lower bound on the size of the universe, if closed


Why does thermal radiation only occur at infrared and visible frequencies?


Why does the action $S=\int L dt=\int (T-V) dt$ have to be minimised (or maximised) to produce Newton's Second Law?


Do physicists talk about instants and infinitely small moments in time?


How to measure distance between object and mobile phone using camera?


Why doesn't the Sun gravitate Mercury so that in following years, Mercury goes inside the Sun?

How does Newtonian mechanics explain why orbiting objects do not fall to the object they are orbiting?


Why would spacetime curvature cause gravity?


Clarification on circular motion and pseudo-forces


How do we know that the charges in an electron and a proton are equal?

Why do electron and proton have the same but opposite electric charge?


How does an AC circuit get anything done?


In the given figure end A is connected to positive terminal and B with negative terminal of a 10 volts battery. How exactly will the current flow?

Detecting if resistances are parallel or series in complex circuits


General Relativity for an orbiting object

What is the correct formula for gravitational time dilation for a satellite in a circular orbit?


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


Are mass and force defined simultaneously?

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


Analytical mechanics resource recommendation

Any good resources for Lagrangian and Hamiltonian Dynamics?


Charge conjugation on spinors: Am I missing a (-1)?


Are there physical reasons for breaking this symmetry in biological systems?

Implications of parity violation for molecular biology


Why black holes curve spacetime using their mass and charge?


How to symmetrize the canonical stress-energy tensor?


Would a tennis ball behave like a quantum particle wave and go through racket with an infinite speed, from $\lambda=h/p$ principle?

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