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1500 questions
36
votes
4 answers
What would happen if an accelerated particle collided with a person?
What would happen if an accelerated particle (like they create in the LHC) hit a person standing in its path?
Would the person die? Would the particle rip a hole? Would the particle leave such a tiny wound that it would heal right away? Something…
user60228
36
votes
7 answers
What is the difference between diffraction and interference of light?
I know these two phenomena but I want to know a little deep explanation. What type of fringes are obtained in these phenomena?
36
votes
4 answers
What exactly is a virtual displacement in classical mechanics?
I'm reading Goldstein's Classical Mechanics and he says the following:
A virtual (infinitesimal) displacement of a system refers to a change in the configuration of the system as the result of any arbitrary infinitesimal change of the coordinates…
Gold
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36
votes
5 answers
Is there a physical system whose phase space is the torus?
NOTE. This is not a question about mathematics and in particular it's not a question about whether one can endow the torus with a symplectic structure.
In an answer to the question
What kind of manifold can be the phase space of a Hamiltonian…
joshphysics
- 58,991
36
votes
2 answers
Energy-Momentum Tensor in QFT vs. GR
What is the correspondence between the conserved canonical energy-momentum tensor, which is $$ T^{\mu\nu}_{can} := \sum_{i=1}^N\frac{\delta\mathcal{L}_{Matter}}{\delta(\partial_\mu f_i)}\partial^\nu f_i - \eta^{\mu\nu}\mathcal{L}$$ (the four…
PPR
- 2,234
36
votes
2 answers
What does it mean that there is no mathematical proof for confinement?
I see this all the time* that there still doesn't exist a mathematical proof for confinement. What does this really mean and how would a sketch of a proof look like?
What I mean by that second question is: what are the steps one needs to prove in…
Physics_maths
- 5,717
36
votes
6 answers
Why is superdeterminism generally regarded as a joke?
Before anything, I'm sorry for being an outsider coming to opine about your field. This is almost always a stupid decision, but I do have a good justification for this case. I've been reading about superdeterminism and it bothered me that most of…
MaiaVictor
- 1,992
36
votes
10 answers
Why are extra dimensions necessary?
Some theories have more than 4 dimensions of spacetime. But we only observe 4 spacetime dimensions in the real world, cf. e.g. this Phys.SE post.
Why are the theories (e.g. string theory) that require more dimensions taken seriously by scientists?…
Fakrudeen
- 761
36
votes
7 answers
Why can't you hear music well over a telephone line?
Why can't you hear music well well over a telephone line?
I was asked this question in an interview for a university study placement and I unfortunately had no idea.
I was given the hint that the telephone sampling rate is 8000 samples per second.
Danny Rancher
- 499
36
votes
8 answers
Do the laws of physics evolve?
Hubble's constant $a(t)$ appears to be changing over time. The fine stucture constant $\alpha$, like many others in QFT, is a running constant that varies, proportional to energy being used to measure it. Therefore, it could be agued that all…
qftme
- 1,870
35
votes
4 answers
Are atoms unique?
Do atoms have any uniquely identifying characteristic besides their history?
For example, if we had detailed information about a specific carbon atom from one of Planck's fingerprints, and could time-travel to the cosmic event in which the atom…
Charles Burns
- 423
35
votes
4 answers
Is there a fundamental reason why gravitational mass is the same as inertial mass?
The principle of equivalence - that, locally, you can't distinguish between a uniform gravitational field and a non-inertial frame accelerating in the sense opposite to the gravitational field - is dependent on the equality of gravitational and…
ravithekavi
- 651
35
votes
4 answers
Explain reflection laws at the atomic level
The "equal angles" law of refection on a flat mirror is a macroscopic phenomenon. To put it in anthropomorphic terms, how do individual photons know the orientation of the mirror so as to bounce off in the correct direction?
yrodro
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35
votes
5 answers
What are the fields produced around a current carrying conductor?
If you consider a current carrying conductor, every instant an electron enters the conductor, another electron will be leaving the conductor. Thus, the current carrying conductor will not be charged (i.e. it would not have any net positive or…
Sensebe
- 5,889
35
votes
5 answers
How do you calculate the anomalous precession of Mercury?
One of the three classic tests of general relativity is the calculation of the precession of the perihelion of Mercury's orbit.
This precession rate had been precisely measured using data collected since the 1600's, and it was later found that…
David Z
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