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"I would never die for my beliefs because I might be wrong."

-- Bertrand Russell


Feb
1
comment Can light be launched outwards from an event horizon?
Read up on lightcones a bit first, the last picture shows what happens in the black hole case. If that doesn't answer your question yet, I'll try to write a full reply.
Feb
1
comment Can light be launched outwards from an event horizon?
Escape velocity is really a Newtonian concept. The event horizon is not defined in terms of escape velocity, but rather as the boundary of a region beyond which the outside world can not be affected anymore. Another way to express this is by looking at what happens with light cones in the geometry of a black hole. As you get closer to the whole, the future light cone tips towards the black hole. On the event horizon, it lies completely inside the boundary.
Feb
1
comment Can light be launched outwards from an event horizon?
The thing is, once you're on the horizon, there does not exist an "outward" direction anymore.
Jan
31
comment About Boltzmann H-theorem
Could you specifically reference the derivation you mention. The assumptions should be in there. But just out of the top of my head, you're going to have to assume some specific initial conditions (they have to be "typical"). The way Boltzmann did it was with the Stosszahlansatz. But more modern derivations use more explicit assumptions on the initial conditions.
Jan
20
comment According to relativity, can a statement be true and false in same time?
What has relativity to do with it? If Newton wrote "It's 1766." and you read the statement now, does that make the statement false or true?
Dec
24
comment Is that true that neutron activity on Earth in 2013 is unusual?
Just skimming through the topics on that website, I'd take anything coming from there with a pinch of salt. Has it been published in a peer-reviewed journal?
Dec
7
comment Electron double slit experiment and the electric field
The field will interfere too, and in such a way that you won't be able to tell, from measuring it, through which slit the electron went.
Nov
12
awarded  Yearling
Oct
28
awarded  Nice Answer
Oct
19
awarded  Taxonomist
Jul
29
comment Why terminal velocity exists?
@ZoltánSchmidt: You seem to be confused by something else as well. A body can keep accelerating while never reaching the speed of light. See Rindler coordinates.
Jul
14
comment Education : Students devising and solving their own problems
@udiboy: note it was only a critique for discouraging own investigations. As you'll note, I pretty much give the same suggestions as you do.
Jul
14
answered Education : Students devising and solving their own problems
Jul
9
comment What's wrong with this QFT thought experiment?
How does Bob encode information in the particles?
Jul
6
revised Time to immerse in a fluid
added 448 characters in body
Jul
6
revised Time to immerse in a fluid
added 29 characters in body
Jul
6
revised Time to immerse in a fluid
added 1 characters in body
Jul
6
revised Time to immerse in a fluid
edited body
Jul
6
comment Time to immerse in a fluid
@udiboy: I think the sphere is somewhat harder but more realistic. With the other forms, I would have to make an additional assumption of how the piece drops into the fluid to be able to compute things. With the sphere, it obviously doesn't matter.
Jul
6
comment Time to immerse in a fluid
@udiboy: Yes, but as you can see, calculus is unavoidable. The final formula, whatever the method you use to arrive at it will contain an integral. Of course, you could maybe partly guess a simplified formula by some dimensional analysis I suppose.