Recent content by Asher Weinerman

I think we all understand each other at this point and nothing further is being added.

If you are talking about the expansion of space then x = 0 locally. If you are talking about Special rel then velocity is symmetric between two objects. In the described case length x is contracted as well. However I think I gave a clue to the answer of my own question when I said that...

What I should have asked at the end of my last statement is "If objects are "appearing" to slow down at the cosmic event horizon what is causing that? Can you point to an equation?

(dr/dt above given for an object dropped from infinity at rest)

A redshift makes objects appear redder but it doesn't make objects appear to slow down. For example in Special Relativity an object traveling away from you appears redder but obviously doesn't slow down (an object traveling away from you at near light speed "appears" visually to be traveling at...

no, he isn't.

Hi Thanks Ibix. I also thought the Hubble law was pretty straightforward, not predicting any slowdown. But every once in a while I come across an expert talking about asymptotic behaviour at the CH. What do you make of the video below of Leonard Susskind. Check out the timestamp 39:32. Is he...

So do objects just sail straight through the cosmological horizon or do they just asymptotically approach it as time here on Earth goes to infinity?

I'm confused whether Hubble's Law applies to objects near the cosmological horizon (CH). I'm told that objects asymptotically approach the CH and freeze there (v -> 0) in the same way that occurs during in-fall towards a black hole. But Hubble's Law says that velocity is proportional to...

PeterDonis, I'm no expert as I've stated before, but Hawking Radiation evaporates black holes in finite time (approx. 10^68 years or something) - this is not my personal theory - many sources quote this estimate or 'round about. If you can tell me how long it takes to fall through the horizon...

Jimmycricket, I had the same question. My view is that not only would all the stars burn out, but all the black holes would evaporate by Hawking Radiation before you crossed the horizon, including the one you are falling into. As for separating the time dilation effect into kinematic and...

Sure. Let the proper time between two events at a fixed location r1 be τ. Trivial integration of the Schwartzchild metric yields the result that an observer at radial coordinate r2 will measure the time between the two events to be τ√(1-2GM/r2)/√(1-2GM/r1). Similarly an observer at position r3...

Incorrect. We can set up two clocks that are synchronized in our reference frame a certain distance apart, and measure the time between events that happen at each clock, say an infalling observer passing clock 1 and then clock 2. This is not a scalar and will be different in some other reference...

That is precisely my point - be wary of transforming to alternate coordinate systems and then misinterpreting them because the new coordinates have obscure meanings. As for the postulates of General Relativity, they are just the equivalence principal and that physical laws must be expressed in...

I notice there is a lot of confusion regarding how long it takes to cross the event horizon as I tried to explore in a different thread. Measuring time by bouncing "time-stamped light signals off an infalling observer may help with measuring proper time which of course will be finite, but it...