# All Questions

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### Does the (relativistic) mass change? Why?

I learned recently that when an object moves with a velocity comparable to the velocity of light the (relativistic) mass changes. How does this alteration take place?
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### Why water will stay on a piece of toilet paper?

I think everyone has tried to blow air (breath) on toilet papers. The papers will get wet. I believe the holes diameters on a toilet paper should be much larger than diameters of water molecules. (The ...
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### Is it normal for physical functions to lack a 2nd derivative?

My question is about the appearance of a non-analytic function in the formula for the resistive force in air or other medium. Considering the 1-dimensional case as covered by Walter Lewin in his 8.01 ...
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### Why is it that protons and electrons have exactly the same but opposite charge? [duplicate]

Possible Duplicate: Why do electron and proton have the same but opposite electric charge? Doesn't it seem very curious that one is an elementary particle and the other a subatomic particle ...
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### Charge Analog of the Higgs Boson?

Since mass can be given to particles via the interaction with the Higgs Field could there be a "Charger Field" that supplies particles with charge? Possibly this would require two different "charger ...
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### what is the relationship between these two sorts of anomalies?

Recently there has been a few questions about anomalies in QFTs: Why do some anomalies (only) lead to inconsistent quantum field theories Classical and quantum anomalies In these, people have been ...
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### Winding Rubber Band

How could you store the kinetic energy of a soda-bottle using a rubber band so that it unwinds after being rolled across a flat surface? Basically, how can you make a bottle roll back after being ...
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### Do the four fundalmental forces of physics have a constant acceleration as gravity [closed]

Do the four fundalmental forces of physics have a constant acceleration as gravity?
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### What is better than time-dependent perturbation theory if the pointer states aren't energy eigenstates?

Time-dependent perturbation theory works excellently if the interaction is weak and the pointer states are approximately energy eigenstates. However, what if the pointer states are not remotely energy ...
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### How can one know if a theory allow action at a distance effects or not?

1-In general, if a theory has action at a distance effects, where can that appear exactly in the theory? 2-Does it appear in the dynamical law of the theory? (does it appear in Newton's 2nd law? ...
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### Why do some anomalies (only) lead to inconsistent quantum field theories

In connection with Classical and quantum anomalies, I'd like to ask for a simple explanation why some anomalies lead to valid quantum field theories while some others (happily absent in the standard ...
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### How does nature prevent transient toroidal event horizons?

How does nature prevent transient toroidal event horizons?.. and does it really need to? Steps to construct a (transient) toroidal event horizon in a asymptotically flat Minkowski spacetime: take a ...
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### What are the properties of the partially polarized light on refraction?

When a ray of ordinary light is passed on the surface of the water the reflected light will be completely polarized( vibrations in one plane). My question is what will be plane of vibration in the ...
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### At what rate does radiation exposure occur at high-c speeds?

If a future astronaut travelled to Alpha Centauri at a significant percentage of light-speed? Apart from increased blue shifted radiation from their direction of travel - how would they experience ...
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### How is the 'cluster decomposition principle' implemented in holographic theories?

Since holographic theories are non-local by definition, how is this principle implemented? Naively, it seems to me it is not, at least, in some sense. I would appreciate an explanation as simple ...
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### What is the equation of the gravitational potential in general relativity?

How is the gravitational potential replaced by the metric tensor in general relativity? $$U_G=\frac {GMm}{r}$$ What is its equation?
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### Does reactive force require the two force involved have to have two different medium for reactive force to occur?

Does reactive force require the two force involved have to have two medium for reactive force to occur? I know the fuel-thruster is working on vacuum space, but we human could not use arm to swim in ...
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### Hanging a Hammock

I have a hammock that I want to hang using a tree on one end and a wooden post set in a bucket of cement on the other end. How would I determine how heavy the cement needs to be so that it would ...
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### Mathematical derivation of $N(\lambda)d\lambda$

We all know that in Rayleigh-Jeans law, $$N(f)df ~=~ 8\pi f^2 df/c^3.$$ How do you derive $N(\lambda)d\lambda$? I am sort of confused...
I could, for example calculate the electric field near a charged rod of infinite length using the classic definition of the electric field, and integrating the: $$\overrightarrow{dE} = \frac{dq}{4 ... 2answers 98 views ### What allows new born suns to travel away from each other? What allows massive new born suns to move away from each other, as they have been observed. I would think that their massive gravity would prevent this and cause them to slam into each other. 1answer 329 views ### Could the Higgs boson field be responsible for the dramatic mass increase when an object begins to travel close to the speed of light? could the Higgs boson field be responsible for the dramatic mass increase incurred when an object nears the speed of light? 2answers 448 views ### Can inductance or resistance be negative or “infinite”? Since the potential different or voltage drop is positive (am I allow to say voltage drop or potential difference in the presence of a changing current?), the current flows from right to left since ... 3answers 258 views ### Could dark energy be powered by force particles that obey quantum mechanics? From what (little) I know about physics, I understand that the universe is expanding due to dark energy, and I understand that no one quite understands it yet. I also understand that the cosmic ... 1answer 271 views ### Does spontanous symmetry breaking affect Noethers theorem? Does spontanous symmetry breaking affect the existence of a conserved charge? And how does depend on whether we look at a classical or a quantum field theory (e.g. the weak interacting theory)? ... 2answers 5k views ### What is the escape velocity of a Black Hole? The escape velocity of Earth is v=\sqrt{\frac {2GM}{R}}, where M is the mass of the Earth and R it's radius (approximating it as a sphere), and is much less than light speed c. But I want to ... 4answers 1k views ### Questions from elevator ride I like to play inside the lift (elevator). For instance, there are bars attached at the side of the lift, and I like to hold my body up using my two hands on the bar. I realised that I actually feel ... 2answers 468 views ### Entanglement: Is it possible to prepare and reset probabilities to send information? I'm pretty certain that the answer to the question in the title is a no, but I don't understand why. I have some basic misunderstanding of quantum processes that I’d like clarified in the form of ... 3answers 266 views ### How to compute the speed necessary for an airplane to fly? I give some physics lessons to a friend. She asked me a question that I am unable to answer. Could you help me ? A plane has a weight of 2\times10^6kg. The surface of the wing is 1200 \text{m}^2. ... 2answers 591 views ### Is there an analogue of configuration space in quantum mechanics? In classical mechanics coordinates are something a bit secondary. Having a configuration space Q (manifold), coordinates enter as a mapping to \mathbb R^n, q_i : Q \to \mathbb R. The primary ... 4answers 397 views ### Is dimensional analysis used outside fluid mechanics and transport phenomena? Most dimensionless numbers (at least the ones easily found) used for dimensional analysis are about fluid dynamics, or transport phenomena, convection and heat transfer - arguably also sort of fluid ... 1answer 107 views ### undergrduate physics courses in American colleges [closed] I am just curious as a non-US person: how does undergraduate physics course progress in U.S. colleges? Do they go right into classical mechanics books, or do they teach introductory courses first, ... 2answers 739 views ### Using Lorentz Invariance of Charge To Calculate Current Density I'm attempting a problem from Zwiebach: A First Course in String Theory and am completely stuck. Could anyone give me a hint? The problem is as follows. Consider S, S' two Lorentz frames with ... 1answer 1k views ### Does the large red shift value of galaxies mean they are far away? When the red shifts of galaxies are large, why do we think that they are far away? I know about Hubble's law, Tully-Fisher relation of spiral galaxies, Faber-Jackson relation of elliptical ... 1answer 477 views ### Applying uncertainty principle and the difference in \Delta x These two questions seem to be very similar, but the textbook uses a bit different methods for calculating \Delta x of uncertainty principle. Question A) Suppose that there is a room with the same ... 1answer 362 views ### Is momentum conservation for the classical Schrödinger equation due to non-relativistic or due to some more exotic invariance? I had no problem appliying the Neothers theorem for translations to the non-relativistic Schrödinger equation \mathrm i\hbar\frac{\partial}{\partial t}\psi(\mathbf{r},t) \;=\; \left(- ... 0answers 94 views ### usage of partition function in some number of particles in one-dimensional axis I just learned some introductory quantum meachnics, but not statistical mechanics, so I am curious how partition functions would be used in the following case: Suppose there are three particles in ... 5answers 1k views ### Gravitation is not force? Einstein said that gravity can be looked at as curvature in space- time and not as a force that is acting between bodies. (Actually what Einstein said was that gravity was curvature in space-time and ... 5answers 3k views ### How much force is required to propel a bicycle? A friend of mine had an idea to attach a motor to a bicycle with the idea to be able to turn it on and have it maintain average bike speed, apparently 15-20 mph. Neither of us have taken physics ... 3answers 1k views ### Does a toy top weigh less when it is spinning? I am under the understanding that a toy top will weigh less when it is spinning. The Russians made a spinning type transport back in the 70s to lessen its payload over the tundra. Is this an effective ... 3answers 266 views ### How can we be sure about the constancy of atomic clocks as in the Hafele and Keating time dilation test? Atomic clocks were used in Hafele and Keatings experiment which supposedly helped to prove time dilation. Time Dilation Proof - Hafele and Keating How can we be sure other forces didn't act upon the ... 1answer 755 views ### Topological phase Can anybody tell me, if generically any system, which is solely described by a topological field theory, resides in a topological phase? I cant find any clear notion of topological phase. Only ... 2answers 740 views ### Euler angle: space-fixed vs body-fixed axes I am sooo confused!! Between active and passive, intrinsic and extrinsic, vectors and basis .... Stipulate that we stick to active rotations only. Then Standard derivation of R(\alpha, ... 1answer 378 views ### Cellular automata rules for quantum mechanics My limited understanding of quantum theory is that a quantum system is completely described by its wave function, which deterministically evolves according to Schrödinger's equation until wave ... 1answer 49 views ### Is it possible to make use of paper/bill permeate by chemical compound to became a paper-made bullet-proof vest? Is it possible to make use of paper/bill permeate by chemical compound to became a paper-made bullet-proof vest? This is inspired by Greece and Italy tend to have more riot than rest of the Europe ... 2answers 1k views ### How do I integrate the Poisson equation to determine the electric potential along a particular direction (e.g., z)? This question is a sequel of sorts to my earlier (resolved) question about a recent paper. In the paper, the authors performed molecular dynamics (MD) simulations of parallel-plate supercapacitors, ... 2answers 604 views ### Proof of charge existence on a grounded conductor A question regarding the existence of charge on grounded conductors is confusing me. Could there be charge on a grounded conductor? How does this not contradict Gauss's Law? Since every conductor ... 1answer 261 views ### How can one know if one has a Majorana fermion? If the Majorana fermion is a fermion that is it's own antiparticle and exactly the same as its fermion counterpart, then how do they know that it's not just a fermion? 2answers 3k views ### Can the equation v=\lambda f be made true even for non sinusoidal waves? The known relation between the speed of a propagating wave, the wave length of the wave, and its frequency is$$v=\lambda f which is always true for any periodic sinusoidal waves. Now consider: ...
I read that an object at rest has such a stupendous amount of energy, $E=mc^2$ because it's effectively in motion through space-time at the speed of light and it's traveling through the time dimension ...