Linked Questions

8
votes
3answers
2k views

How can black hole increase its mass? [duplicate]

From observer point of view an object, which falls into black hole never crosses its horizon. Then how does black hole appears and grows its mass? Or does any black hole looks (and feels by all other ...
11
votes
2answers
1k views

Black hole formation as seen by a distant observer [duplicate]

Possible Duplicate: How can anything ever fall into a black hole as seen from an outside observer? Is black hole formation observable for a distant observer in finite amount of time? Specifically,...
3
votes
2answers
1k views

Possible paradox with black holes and time dilation [duplicate]

I am by no means an expert in the realm of physics. I do from time to time, try to understand the concepts of modern physics and their applications. I came across this video that I am currently ...
0
votes
3answers
789 views

Formation of the event horizon seems impossible with singularity inside seems impossible [duplicate]

According to what I was reading, the formation of an event horizon appears if the mass becomes compact enough. Unfortunately, due to time dilation the time for mass to fall into the event horizon ...
0
votes
1answer
578 views

Does infalling matter ever cross the event horizon? [duplicate]

Assume you are immortal, then say if you fell towards a blackhole, to an observer far away you will appear to slow down as you approach event horizon and gradually come to stand still. However for ...
4
votes
0answers
489 views

How can things at the event horizon slow down and appear to stop to a remote observer? [duplicate]

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 ...
2
votes
2answers
376 views

If you fall in a black hole, when do you go past the event horizon? [duplicate]

Say I fall into the event horizon of a black hole. As I cross the black hole, I would appear to outside onlookers to freeze in time, and would never move from that point again. In my perspective, time ...
0
votes
1answer
316 views

How can black hole get mass if nothing can pass its event horizon? [duplicate]

External observer will never see any mass crossing event horizon - any object near it would appear frozen, red-shifted and then disappearing. In this case - how black hole can possibly get any mass ...
0
votes
1answer
208 views

Is this answer stating that an external observer can see a black hole mass grow, correct? [duplicate]

Is this answer from here stating that an external observer can see a black hole mass grow, correct? This question (is an external observer can ever see the mass of a black hole increase--motivated ...
1
vote
1answer
181 views

Gravitational time delay and contraction of matter [duplicate]

How can any matter contract to its Schwarzschild radius if gravitational time dilation clearly states that all clocks stop at that point. So any contraction any movement would stop. If that is so why ...
0
votes
1answer
149 views

For a distant observer can a black hole form and grow in finite time? [duplicate]

Consider an observer at a significant distance away from a collapsing star. As such when a singularity is born at the core of the star the observer would never see it grow anymore than the ...
0
votes
1answer
52 views

Can we observe something on just the horizon of a black hole? [duplicate]

It is not clear to me if we can observe matter infalling to a black hole. When it is stated that time stretch to infinite for an external observer, then we should see a kind of accretion or jam at the ...
1
vote
0answers
67 views

Can matter actually cross the event horizon effectively falling into a Black hole? [duplicate]

The answers I have seen do not take into effect the growth of the radius of the event horizon as significant amounts of matter get close to the existing event horizon. I would have expected that ...
1
vote
0answers
66 views

Can matter actually go “inside” a black hole? [duplicate]

Pardon my question but I am no astro-physicist. If a black hole is a singularity, A.K.A. a single point in space-time which is infinitely small and which has an infinitely high density, can matter ...
0
votes
1answer
96 views

How can black holes be observed to grow? [duplicate]

If, from the reference frame of an observer at rest outside a black hole, it takes an infinite amount of time for an object to be observed to fall into a black hole, how can black holes ever be ...
0
votes
1answer
54 views

Black Holes and Time [duplicate]

My understanding is that if I am outside a black hole and watch something fall in, the object will appear to slow down and will never actually get sucked in. So how can we ever get a black hole if ...
1
vote
0answers
44 views

Thoughts on Black Holes [duplicate]

Given that time slows to a stand-still at the event horizon of a Black Hole, how long would it take a black hole to form, from the perspective of an outside observer? It would seem, as a massive star ...
1
vote
0answers
33 views

Black Holes should take infinite time to form with the increase in mass to form one [duplicate]

How can black hole form because as the density begins to increase gravity also start to increase and time starts to slow. wouldn't it take infinite time to form a black hole. how can anything fall ...
1
vote
0answers
26 views

Can one observe a blackhole grow from outside its event horizon? [duplicate]

For an observer outside Black hole's event horizon nothing ever falls into the black hole . So if the observer waits for an eternity outside a super massive blackhole feeding on gas , will the ...
391
votes
16answers
39k views

How does gravity escape a black hole?

My understanding is that light can not escape from within a black hole (within the event horizon). I've also heard that information cannot propagate faster than the speed of light. It would seem to ...
62
votes
10answers
9k views

Can black holes form in a finite amount of time?

One thing I know about black holes is that an object gets closer to the event horizon, gravitation time dilation make it move more slower from an outside perspective, so that it looks like it take an ...
35
votes
9answers
8k views

Does any particle ever reach any singularity inside the black hole?

I am not a professional physicist, so I may say something rubbish in here, but this question has always popped in my mind every time I read or hear anyone speak of particles hitting singularities and "...
19
votes
10answers
5k views

How does light behave within a black hole's event horizon?

If the event horizon of a black hole is the distance from the center from within which light cannot escape, imagine a person with a flashlight falls into the black hole. He points his flashlight in a ...
23
votes
7answers
4k views

Can matter really fall through an event horizon?

This question is closely related to Event horizons without singularities from about a year ago (May 2012), which John Rennie answered nicely and persuasively. My variant of the question is this: ...
18
votes
3answers
2k views

So Black Holes Actually Merge! In 1/5th of a Second - How?

I've read a lot of conflicting answers in these forums. However, today saw the awesome announcement of gravitational waves. Two black holes merged: http://www.slate.com/blogs/bad_astronomy/2016/02/11/...
19
votes
2answers
883 views

Black hole no-hair theorems vs. entropy and surface area

I was revisiting some old popular science books a while ago and two statements struck me as incompatible. No-hair theorems: a black hole is fully-described by just a few numbers (mass, spin etc) ...
9
votes
2answers
3k views

What is the physical size of a black hole?

Something that's always confused me. How large is a black hole's physical size - not mass? From descriptions, it would seem that the 'singularity' is a single point, but is it really? Say for ...
15
votes
4answers
2k views

Event horizons without singularities

Someone answered this question by saying that black hole entropy conditions and no-hair theorems are asymptotic in nature -- the equations give an ideal solution which is approached quickly but never ...
3
votes
3answers
19k views

What is the relation between orbital velocity and escape velocity in strongly relativistic situations?

For practical purposes, I'm considering a non-rotating black hole or neutron star, because I find Kerr black holes a little confusing. The ratio between orbital velocity and escape velocity in ...
7
votes
5answers
747 views

Taking selfies while falling, would you be able to notice a horizon before hitting a singularity?

I am generally interested in the role of "pings"(0a) between participants (a.k.a. "signal roundtrips"(0b), as familiar for instance from Synge's "five point curvature detector") in the determination ...

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