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1500 questions
62
votes
7 answers
Why do some lights captured by the Webb telescope have rays and others don't?
On the images captured by Webb telescope one can see some lights with 6 rays, but most others don't have any. One would expect the optics to transform all light sources at infinity in the same manner. What causes these differences?
Michael
- 1,919
62
votes
4 answers
Rigorous underpinnings of infinitesimals in physics
Just as background, I should say I am a mathematics grad student who is trying to learn some physics. I've been reading "The Theoretical Minimum" by Susskind and Hrabovsky and on page 134, they introduce infinitesimal transformations. Here's the…
Brian Klatt
- 893
62
votes
7 answers
Is Biot-Savart law obtained empirically or can it be derived?
There's already a question like this here so that my question could be considered duplicate, but I'll try to make my point clear that this is a different question.
Is there a way to derive Biot-Savart law from the Lorentz' Force law or just from…
Gold
- 35,872
62
votes
3 answers
In substances where light is slowed down, is its momentum lessened and if so, how does it speed up again when emerging from that substance?
I think in some media, light can be significantly slowed down; but even if only slightly, where would the momentum go when the light slows down and where does it get the extra momentum when it leaves that medium? An example is a water.
releseabe
- 2,224
62
votes
12 answers
Are there pure sine waves in nature or are they a mathematical construct that helps us understand more complex phenomena?
I've studied a bit of frequency analysis with FFT and optimal phase binning and was taught that we can represent any composite waveform as the sum of its component frequencies.
I understand the maths works and gives meaningful results that we can…
Schizomorph
- 751
62
votes
6 answers
In what order would light bulbs in series light up when you close a long circuit?
For a few days, I was thinking of this question.
Lets assume we have a simple circuit that is 100 meters long. And lets say that we have bulbs A, B and C connected to the circuit's 30th, 60th and 90th meter relatively (from the + side). When we…
Huzo
- 1,013
62
votes
5 answers
Do photons truly exist in a physical sense or are they just a useful concept like $i = \sqrt{-1}$?
Reading about photons I hear different explanations like "elementary particle", "probability cloud", "energy quanta" and so forth. Since probably no one has ever seen a photon (if "seen" it supposedly - and rather conveniently - ceases to exist) but…
Jens
- 1,282
62
votes
4 answers
Do gravitational waves travel faster than light?
In Feb 12, 2016 edition of Times of India, an article read
[with the discovery of gravitational waves, we will be able to] Track Supernovas hours before they're visible to any telescope because the waves arrive Earth long before any light does,…
Mac164
- 812
62
votes
5 answers
Why is the Moon considered the major cause of tides, even though it is weaker than the Sun?
You have likely read in books that tides are mainly caused by the Moon. When the Moon is high in the sky, it pulls the water on the Earth upward and a high-tide happens. There is some similar effect causing low-tides. They also say that the Sun…
Moctava Farzán
- 1,904
62
votes
3 answers
Why does our voice sound different on inhaling helium?
This question (and answer) is an attempt to clear the air on what appears to be a very simple issue, with conflicting or unclear explanations on the internet. Arguments, negations, etc are invited.
I'm classifying this as a physics question, since…
Dev Kanchen
- 971
62
votes
7 answers
Do electrons have shape?
According to the Wikipedia page on the electron:
The electron has no known substructure. Hence, it is defined or assumed to be a point particle with a point charge and no spatial extent.
Does point particle mean the particle should not have a…
Anil Bharadia
- 730
62
votes
9 answers
Why is it said that without quantum mechanics we would not have modern computers?
I've heard this in many quantum mechanics talks and lectures, nevertheless I don't seem to grasp the idea behind it.
What I mean is, at which point is that our modern understanding of quantum mechanics led to a technological development so…
harogaston
- 885
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61
votes
2 answers
Why do we expect our theories to be independent of cutoffs?
Final edit: I think I pretty much understand now (touch wood)! But there's one thing I don't get. What's the physical reason for expecting the correlation functions to be independent of the cutoff? I.e. why couldn't we just plump for one "master…
Edward Hughes
- 7,876
61
votes
4 answers
Why do prisms work (why is refraction frequency dependent)?
It is well known that a prism can "split light" by separating different frequencies of light:
Many sources state that the reason this happens is that the index of refraction is different for different frequencies. This is known as dispersion.
My…
Brandon Enright
- 11,937
61
votes
2 answers
Difference between $\Delta$, $d$ and $\delta$
I have read the thread regarding 'the difference between the operators $\delta$ and $d$', but it does not answer my question.
I am confused about the notation for change in Physics. In Mathematics, $\delta$ and $\Delta$ essentially refer to the same…
Yuruk
- 899