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1500 questions
49
votes
8 answers
Classical mechanics without coordinates book
I am a graduate student in mathematics who would like to learn some classical mechanics. However, there is one caveat: I am not interested in the standard coordinate approach. I can't help but think of the fields that arise in physics as sections of…
Sean Tilson
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49
votes
3 answers
Can kicking a falling phone save it from shattering?
So I saw this tip
but I don't think this is true, it would be that your leg or shoe is more flexible than a hard floor so the momentum change would be slower right?
Pigeon
- 628
49
votes
6 answers
Why do we need infinite-dimensional Hilbert spaces in physics?
I am looking for a simple way to understand why do we need infinite-dimensional Hilbert spaces in physics, and when exactly do they become neccessary: in classical, quantum, or relativistic quantum physics (i.e. when particles can be created and…
Dee
- 834
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49
votes
12 answers
Are vacuum fluctuations really happening all the time?
In popular physics articles and even some physics classes I've been to, the vacuum of space is described as being constantly full of quantum fluctuations. Supposedly, all sorts of particle-antiparticle pairs at all scales are constantly appearing…
Nathan Reed
- 3,049
49
votes
3 answers
How does water help extinguish fire?
How does water extinguish fire? Heat energy from the fire is transferred to the water, isn't that how it works? How does water deprive oxygen and stop combustion? How is the specific heat of water connected to this? If we use hot water instead cold…
user42836
- 658
49
votes
8 answers
What technology can result from such expensive experiment as undertaken in CERN?
I wonder what technology can be obtained from such very expensive experiments/institutes as e.g. undertaken in CERN?
I understand that e.g. the discovery of the Higgs Boson confirms our understanding matter. However, what can result form this…
dani
- 903
49
votes
5 answers
When a star becomes a black hole, does its gravitational field become stronger?
I've seen in a documentary that when a star collapses and becomes a black hole, it starts to eat the planets around.
But it has the same mass, so how does its gravitational field strength increase?
xxxo
- 525
49
votes
0 answers
$\operatorname{O}(N)$ sigma model at large $N$
I would like to better understand the main principles of large-$N$ expansion in quantum field theory. To this end, I decided to consider a simple toy model with lagrangian (from Wikipedia)
$
\mathcal{L} = \frac{1}{2}(\partial_{\mu}…
user43283
- 865
49
votes
7 answers
Why don't two musical instruments sometimes generate destructive interference?
I'm an electrical engineer, and I understand wave propagation, interference patterns, and so on. But I'm missing something basic, so perhaps my understanding isn't as good as I believe. I'll show my thinking; please tell me where I am mistaken.
Say…
bitsmack
- 718
49
votes
2 answers
Why Do Sausages Always Split Lengthwise?
Sausages universally split parallel to the length of the sausage. Why is that?
Dale
- 6,014
48
votes
2 answers
Weak force: attractive or repulsive?
We are always told that there are the four fundamental forces or interactions of nature: gravitation, electromagnetism, and the weak and strong forces. We know that gravitation is attractive, that electromagnetism can be attractive or repulsive…
user50229
- 975
48
votes
16 answers
Why is radioactive half-life constant?
Say you have just four radioactive atoms with a half-life of one hour. (I am using a small number of atoms to keep it simple and illustrate my confusion more clearly). So that means one hour from now, two of the atoms will have decayed (on average)…
Luke B
- 605
48
votes
2 answers
What is the weight equation through general relativity?
The gravitational force on your body, called your weight, pushes you down onto the floor.
$$W=mg$$
So, what is the weight equation through general relativity?
user17093
48
votes
8 answers
Amplitude of an electromagnetic wave containing a single photon
Given a light pulse in vacuum containing a single photon with an energy $E=h\nu$, what is the peak value of the electric / magnetic field?
Andrey S
- 1,046
48
votes
2 answers
Why didn't Lorentz conclude that no object can go faster than light?
Based on Lorentz factor $\gamma = \frac{1}{\sqrt {1-\frac{v^2}{c^2}}}$ it is easy to see $v < c$ since otherwise $\gamma$ would be either undefined or a complex number, which is non-physical. Also, as far as I understand this equation was known…
Rob
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