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1500 questions
137
votes
2 answers
Reading the Feynman lectures in 2012
The Feynman lectures are universally admired, it seems, but also a half-century old.
Taking them as a source for self-study, what compensation for their age, if any, should today's reader undertake? I'm interested both in pointers to particular…
David Feldman
- 1,481
137
votes
15 answers
Is the butterfly effect real?
Is the butterfly effect real? It is a well-known statement that a butterfly, by flapping her wings in a slightly different way, can cause a hurricane somewhere else in the world that wouldn't occur if the butterfly had moved her wings in a slightly…
135
votes
11 answers
Is anti-matter matter going backwards in time?
Some sources describe antimatter as just like normal matter, but "going backwards in time". What does that really mean? Is that a good analogy in general, and can it be made mathematically precise? Physically, how could something move backwards in…
Gerard
- 6,791
134
votes
1 answer
Linear sigma models and integrable systems
I'm a mathematician who recently became very interested in questions related to mathematical physics but somehow, I faced difficulties in penetrating the literature... I'd highly appreciate any help with the following question:
My aim is to relate…
user5831
- 1,331
134
votes
15 answers
What happens to the energy when waves perfectly cancel each other?
What happens to the energy when waves completely cancel each other out via destructive interference? It seems like the energy just disappears, but that would violate the law of energy conservation.
My guess is that the kinetic energy is transformed…
aortizmena
- 1,516
132
votes
5 answers
Why does paper cut through things so well?
Paper is an extremely flexible material, at least when it is in sheet form. It will deform significantly according to the pressure applied and it is easy to fold.
Therefore, it's extremely counterintuitive that a sheet of paper could cut through…
132
votes
2 answers
Why does ice cream get harder when colder?
What would seem to be a silly question actually does have some depth to it. I was trying to scoop out some of my favorite soft name-brand ice cream when I noticed it was frozen solid, rather than its usual creamy consistency. After leaving it out…
TheEnvironmentalist
- 2,716
132
votes
21 answers
Books for general relativity
What are some good books for learning general relativity?
Pratik Deoghare
- 5,609
132
votes
3 answers
Why is the vibration in my wire acting so oddly?
I was soldering a very thin wire today, and when I had one end firmly soldered, I accidentally bumped the wire diagonally with my tweezers. What I'd expect to happen is that the wire oscillates for a little while in one axis, then stops. However,…
0xDBFB7
- 1,179
131
votes
4 answers
Why can I touch aluminum foil in the oven and not get burned?
I cook frequently with aluminum foil as a cover in the oven. When it's time to remove the foil and cook uncovered, I find I can handle it with my bare hands, and it's barely warm.
What are the physics for this? Does it have something to do with…
Jason P Sallinger
- 1,305
130
votes
15 answers
How can anything ever fall into a black hole as seen from an outside observer?
The event horizon of a black hole is where gravity is such that not even light can escape. This is also the point I understand that according to Einstein time dilation will be infinite for a far-away-observer.
If this is the case how can anything…
Matt Luckham
- 1,697
130
votes
2 answers
On this infinite grid of resistors, what's the equivalent resistance?
I searched and couldn't find it on the site, so here it is (quoted to the letter):
On this infinite grid of ideal one-ohm resistors, what's the equivalent resistance between the two marked nodes?
With a link to the source.
I'm not really sure if…
Malabarba
- 5,061
129
votes
8 answers
Does a particle exert force on itself?
We all have elaborative discussion in physics about classical mechanics as well as interaction of particles through forces and certain laws which all particles obey.
I want to ask,Does a particle exert a force on itself?
EDIT
Thanks for the…
Shreyansh Pathak
- 3,339
129
votes
11 answers
Why does Newton's Third Law actually work?
My father explained to me how rockets work and he told me that Newton's Third Law of motion worked here. I asked him why it works and he didn't answer. I have wasted over a week thinking about this problem and now I am giving up.
Can anyone explain…
user164594
128
votes
8 answers
What is $\Delta t$ in the time-energy uncertainty principle?
In non-relativistic QM, the $\Delta E$ in the time-energy uncertainty principle is the limiting standard deviation of the set of energy measurements of $n$ identically prepared systems as $n$ goes to infinity. What does the $\Delta t$ mean, since…
Hobo
- 1,305