A black hole is a volume from which photons, or any matter, can not escape. More formally, the coordinate speed of light at the event horizon - the boundary of a black hole - is zero, as measured by a sufficiently separated observer.
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Will the Big Rip tear black holes apart?
There seems to be an obvious contradiction between the predictions of the physics of black holes and the Big Rip, a predicted event about 16.7 Gyr in the future where local groups, galaxies, solar ...
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How will a super massive black hole effect our galaxy?
I've recently learned that the general consensus is that several (if not, most) galaxies have super massive black holes in their center, in particular the Milky Way. This, at least to me, makes ...
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From the perspective of an observer inside a black hole's horizon, where does the energy for Hawking radiation come from?
Would energy be seen to "flow" to the outside of the black hole? Through what mechanism?
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Does the curvature of space-time cause objects to look smaller than they really are?
What's the difference between looking at a star from a black hole and looking at it from empty space?
My guess is that the curvature of space-time distorts the wavelength of light thus changing the ...
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Kerr solution for finite collapse time
The Kerr black hole solutions gives an analytic continuation that is asymptotically flat. Some people have argued that this is another universe, but others state that the analytic continuation ...
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Falling into a black hole
I've heard it mentioned many times that "nothing special" happens for an infalling observer who crosses the event horizon of a black hole, but I've never been completely satisfied with that statement. ...
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Will acceleration rate of expansion of space become faster than speed of light?
From watching cosmology lectures, it seems that the space between galaxies is expanding at an accelerating rate, my question is since it is the space that is (acceleratingly expanding), the special ...
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Do black holes play a role in quantum decoherence?
Sorry for such a vague question but I could have sworn I read somewhere that Hawking proposed the reason we might see a classically appearing universe is due to the possible role of black holes in ...
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Deriving Birkhoff's Theorem
I am trying to derive Birkhoff's theorem in GR as an exercise: a spherically symmetric gravitational field is static in the vacuum area. I managed to prove that $g_{00}$ is independent of t in the ...
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Do black holes accelerate in spin as they obtain more mass?
It is known that - When a star collapses during the formation of the black hole, the black hole obtains the spin of the star which it collapsed from...
What I'd like to know is, If this spin ...
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387 views
What happens to a photon in a black hole?
Assume a photon enters the event horizon of a black hole. The gravity of the black hole will draw the photon into the singularity eventually. Doesn't the photon come to rest and therefore lose it's ...
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Do singularities have a “real” as opposed to mathematical or idealized existence?
I was thinking of, for example a Schwarzchild metric at r=0, i.e. the gravitational singularity, a point of infinite density. I realise that there are different types of singularities--timelike, ...
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Gravitational Redshift around a Schwarzschild Black Hole
Let's say that I'm hovering in a rocket at constant spatial coordinates outside a Schwarzschild black hole.
I drop a bulb into the black hole, and it emits some light at a distance of $r_e$ from the ...
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The role of dark matter in black holes and star formation
In my understanding, there exists a critical mass for which a star needs to be in order for it to collapse into a black hole. This also applies to a certain critical density of gas in order for stars ...
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How do you explain the observed fact that “black hole” objects move?
As per Newton objects with mass attract each other, and per Einstein this is further explained by saying that mass warps space-time. So a massive object makes a "dent" into space-time,
a gravity well. ...
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Would the universe get consumed by blackholes because of entropy?
Since the total entropy of the universe is increasing because of spontaneous processes, black holes form because of entropy (correct me if I'm wrong), and the universe is always expanding, would the ...
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Why can't light escape from inside event horizon of Black Holes?
The simple answer: Its because Gravity of Black Hole there doesn't allow it. See also this and this Phys.SE posts.
Isn't it a classical answer? When we're unable to connect Gravity with Quantum ...
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is gravity always the weakest force [duplicate]
Possible Duplicate:
What does it mean to say “Gravity is the weakest of the forces”?
Strongest force in nature
It is usually taught that the gravitational force is the weakest ...
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Where 2 comes from in formula for Schwarzschild radius?
In general theory of relativity I've seen several times this factor:
$$(1-\frac{2GM}{rc^2}),$$
e.g. in the Schwarzschild metric for a black hole, but I still don't know in this factor where 2 comes ...
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How can things at the event horizon slow down and appear to stop to a remote observer?
So they say the remote observer will never see anything fallen to the black hole, because any object will slow down as it gets closer to the event horizon and eventually stop to stay there forever. Am ...
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Primordial Black Hole Detection
There's ample direct evidence for the existence of galactic and stellar mass black holes. However, there is no such direct evidence of primordial black holes, those formed after the Big Bang. A recent ...
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Has Cosmological Natural Selection been disproved?
I've been reading Lee Smolin's Life of the Cosmos.
Great book and it makes a lot of sense that the conditions in black holes are the same as conditions at the big bang.
Question is, has his theory ...
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Can a black hole actually grow, from the point of view of a distant observer? [duplicate]
Possible Duplicate:
Black hole formation as seen by a distant observer
I've read in several places that from the PoV of a distant observer it will take an infinite amount of time for new ...
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265 views
How can black holes be so dense?
It is said that if the Earth were a black hole, it would be the size of a peanut!?
How is this density possible, are atoms really that sparse that they can be compressed so tightly? Is there some ...
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Liquid analog of the Black Hole (Part 2)
Similar question has been asked but did no get good answers.
We know that black hole can confine light, but can we create an ocean black hole -
which can confine surface water waves or sound waves in ...
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Can anything come out from the big bang?
If any configuration of matter can fall into a black hole and hit the singularity, and ditto for the big crunch, and there is time reversal CPT invariance, does it mean anything can pop out of the ...
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Incommensurability between different observers describing the same universe?
According to black hole complementarity, if there is a black hole and Alice falls into it carrying a qubit, but Bob stays out, then Alice can measure the qubit inside the black hole, and confirm it ...
