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1500 questions
120
votes
9 answers
What is the relation between electromagnetic wave and photon?
At the end of this nice video (https://youtu.be/XiHVe8U5PhU?t=10m27s), she says that electromagnetic wave is a chain reaction of electric and magnetic fields creating each other so the chain of wave moves forward.
I wonder where the photon is in…
Xtro
- 1,711
120
votes
6 answers
What are the justifying foundations of statistical mechanics without appealing to the ergodic hypothesis?
This question was listed as one of the questions in the proposal (see here), and I didn't know the answer. I don't know the ethics on blatantly stealing such a question, so if it should be deleted or be changed to CW then I'll let the mods change…
Logan M
- 4,614
119
votes
11 answers
Is Angular Momentum truly fundamental?
This may seem like a slightly trite question, but it is one that has long intrigued me.
Since I formally learned classical (Newtonian) mechanics, it has often struck me that angular momentum (and generally rotational dynamics) can be fully derived…
Noldorin
- 7,547
119
votes
4 answers
Why do clouds have well-defined boundaries?
Why do cumulus clouds have well defined boundaries? In other words, what are the physical mechanisms that hold a cloud together, as an entity separate from other clouds, that prevent it from spreading, etc.
Naively, one could expect the atmospheric…
Roger V.
- 68,984
119
votes
2 answers
Is it necessary to consume energy to perform computation?
As far as I know, today most of the computers are made from semiconductor devices, so the energy consumed all turns into the heat emitted into space.
But I wonder, is it necessary to consume energy to perform computation?
If so, is there a…
jiakai
- 1,243
119
votes
18 answers
How does mass leave the body when you lose weight?
When your body burns calories and you lose weight, obviously mass is leaving your body. In what form does it leave? In other words, what is the physical process by which the body loses weight when it burns its fuel?
Somebody said it leaves the…
exokernel
- 1,355
118
votes
4 answers
Intuitively, why are bundles so important in Physics?
I've seem the notion of bundles, fiber bundles, connections on bundles and so on being used in many different places on Physics. Now, in mathematics a bundle is introduced to generalize the topological product: describe spaces that globally are not…
Gold
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118
votes
6 answers
Why is glass transparent?
Once I asked this question from my teacher and he replied "Because it passes light.". "And why does it pass light?" I asked and he said, "Because it is transparent.".
The same question again, Why glass is transparent? Why does light pass through it,…
SMUsamaShah
- 5,507
118
votes
18 answers
Can the Heisenberg Uncertainty Principle be explained intuitively?
I have heard several pseudoscientific explanations about the Heisenberg Uncertainty Principle and find them hard to believe.
As a mathematician mainly focusing on functional analysis, I have a considerable interest in this matter. Although I still…
D1X
- 1,290
117
votes
6 answers
Are Newton's "laws" of motion laws or definitions of force and mass?
If you consider them as laws, then there must be independent definitions of force and mass but I don't think there's such definitions.
If you consider them as definitions, then why are they still called laws?
user5402
- 3,113
116
votes
11 answers
Is there something similar to Noether's theorem for discrete symmetries?
Noether's theorem states that, for every continuous symmetry of an action, there exists a conserved quantity, e.g. energy conservation for time invariance, charge conservation for $U(1)$. Is there any similar statement for discrete symmetries?
Tobias Kienzler
- 6,950
116
votes
11 answers
Why do fusion and fission both release energy?
I only have high school physics knowledge, but here is my understanding:
Fusion: 2 atoms come together to form a new atom. This process releases the energy keeping them apart, and is very energetic. Like the sun!
Fission: Something fast (like an…
user230910
- 1,151
116
votes
4 answers
Why do electrons, according to my textbook, exist forever?
Does that mean that electrons are infinitely stable? The neutrinos of the three leptons are also listed as having a mean lifespan of infinity.
HyperLuminal
- 1,978
116
votes
6 answers
What is the physical meaning of commutators in quantum mechanics?
This is a question I've been asked several times by students and I tend to have a hard time phrasing it in terms they can understand. This is a natural question to ask and it is not usually well covered in textbooks, so I would like to know of…
Emilio Pisanty
- 137,480
116
votes
1 answer
Superfields and the Inconsistency of regularization by dimensional reduction
Question:
How can you show the inconsistency of regularization by dimensional reduction in the $\mathcal{N}=1$ superfield approach (without reducing to components)?
Background and some references:
Regularization by dimensional reduction (DRed) was…
Simon
- 3,593