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Feb
4
comment What happens when waves of light enter your eye?
I'm voting to close this question as off-topic because is shows insufficient prior research
Feb
4
comment Cherenkov radiation can it happen in a jar using tap water with 8 thorium laced lantern mantles as a radiation source
I would guess the Cherenkov radiation is there but it's too faint to be seen. The blue glow seen in pictures of nuclear storage pools comes from very intense radiation many orders of magnitude higher than your thorium mantles can produce.
Feb
4
comment Cherenkov radiation can it happen in a jar using tap water with 8 thorium laced lantern mantles as a radiation source
Steve, you can edit your question to correct any mistakes.
Feb
4
comment If humanity was to send a probe to Proxima Centauri, how long would the travel last?
Related, though not a duplicate: How long would it take me to travel to a distant star?
Feb
4
comment Shapes in a black hole
The definition of space does not change. The spatial coordinates are defined in exactly the same way inside the horizons as outside them.
Feb
3
comment Shapes in a black hole
I'm afraid that last comment makes no sense. By shape I assume you mean some surface in two of the space like dimensions e.g. a spherical or cubic surface. Assuming this shape can resist tidal forces it won't change shape on crossing either of the horizons.
Feb
3
comment Shapes in a black hole
I don't understand why you think an object falling in will change shape. Apart of course from the effects of tidal forces. The radial and time coordinates don't swap places. All that happens is the light comes tilt over so all time like geodesics have decreasing $r$.
Feb
3
comment Shapes in a black hole
Re your bracketed question about decreasing $r$, the alternative is to travel outwards i.e. with increasing $r$. If you cross the inner horizon in the outward direction then you are forced to travel in the increasing $r$ direction until after you've crossed the outer horizon (and escaped from the black hole).
Feb
3
comment Virtual particles, gravity, and dark matter?
@KeithReynolds: you need to post a fresh question to do justice to this, but for example supersymmetric cancellations can cut off the contributions above some hypothetical supersymmetry scale. The trouble is that scale must be greater than a few TeV or we would have evidence for it from the LHC. Even a few TeV still creates a vacuum energy many orders of magnitude greater than observed. You can of course suggest any random cut-off you want, but without any physical justification you are effectively just moving the problem around.
Feb
3
comment Can so called “space mining” cause a danger to Earth?
I'm voting to close this question as off-topic because it isn't a question about physics
Feb
3
comment Virtual particles, gravity, and dark matter?
@KeithReynolds: for why vacuum/dark energy causes expansion see this answer of mine. You'll have to clarify your first question as I'm not sure what you mean.
Feb
3
comment Virtual particles, gravity, and dark matter?
I freely admit my answer takes considerable liberties in an attempt to give a popular science level explanation. Anyone who thinks it takes unacceptable liberties should downvote and I will respond by deleting my answer. Obviously I think any distortions of the truth are acceptable otherwise I wouldn't have posted it, but I'm willing to go with the majority opinion.
Feb
3
comment Hawking radiation for an observer at infinity
If you're at infinity then the horizon you see is a true one by definition. You only see an apparent horizon if you are a finite distance away.
Feb
3
comment Gauss law-electric field through the spherical surface of a sphere
Hi and welcome to the Physics SE! Please note that this is not a homework help site. Please see this Meta post on asking homework questions and this Meta post for "check my work" problems.
Feb
3
comment Problem in electrostatics
Hi and welcome to the Physics SE! Please note that this is not a homework help site. Please see this Meta post on asking homework questions and this Meta post for "check my work" problems.
Feb
3
comment Why a wave, travelling in a lighter medium, inverts upon reflection from an interface of a denser medium?
Possible duplicate of: Phase shift of 180 degrees on reflection from optically denser medium
Feb
3
comment Can Loop Quantum Gravity and Quantum Field Theory coexist?
@Nick: See How is matter modeled in loop quantum gravity?
Feb
2
comment Can Loop Quantum Gravity and Quantum Field Theory coexist?
This is a meaningless question. At the moment QFT and LQG have completely different domains of applicability.
Feb
2
comment Why is surface tension positive?
The $dW$ in the equation is the work done on the liquid as the area increases, and this is positive. Working out the sign of work is always a bit of a headscratcher, but look at it this way. The energy of the surface increases as its area increases, so the work done on the surface must be positive so it adds to the surface energy.
Feb
2
comment What's the formula for the speed of an accelerating car?
@Farcher: see my answer, with some approximations $\tanh(ct)$ turns out to be the solution.