Linked Questions

132 votes
15 answers
35k views

How can anything ever fall into a black hole as seen from an outside observer?

The event horizon of a black hole is where gravity is such that not even light can escape. This is also the point I understand that according to Einstein time dilation will be infinite for a far-away-...
Matt Luckham's user avatar
  • 1,717
21 votes
5 answers
3k views

Does an object approaching a black hole ever cross the combined event horizon of the black hole and itself?

Once you start studying black holes, one of the first things you'll probably hear is that from an outsider's perspective objects falling into the black hole take an infinite time to do so due to time ...
Giorgos G's user avatar
  • 356
8 votes
4 answers
1k views

A small black hole asymptotically approaches a big black hole's event horizon. Will it seem to be frozen there, or will it seem to merge?

On this site, there are currently two scenarios described: two black holes merge in a finite time in any sensible meaning of the term merge the two black holes do indeed merge in a finite, and very ...
Árpád Szendrei's user avatar
158 votes
3 answers
37k views

Why does Stephen Hawking say black holes don't exist?

Recently, I read in the journal Nature that Stephen Hawking wrote a paper claiming that black holes do not exist. How is this possible? Please explain it to me because I didn't understand what he ...
Devesh Saini's user avatar
  • 1,479
11 votes
2 answers
445 views

Colliding black holes

If objects approaching the event horizon of a black hole appear to slow down to outside observers, how was LIGO able to "see" black holes collide? Wouldn't their collision appear to stop as their ...
J.Oppenheim's user avatar
10 votes
2 answers
556 views

Two observers fall into separate black holes, then the black holes merge, can they meet again?

As far as I understand, both these things take finite time: two black holes merging in any sensible meaning of the term merge the two black holes do indeed merge in a finite, and very short, time. ...
Árpád Szendrei's user avatar
5 votes
2 answers
517 views

Does event horizon expand instantly or does it take time for large black holes?

When something falls into a black hole, its mass increases and its event horizon expands a little to reflect the new mass. In case of very large supermassive black holes, with event horizon spanning ...
toriningen's user avatar
1 vote
2 answers
174 views

Does a finite mass particle pass a black hole event horizon in a finite time for an outside observer?

When we talk about a particle taking an infinite amount of time for it to cross the event horizon in the external observer's point of view, we assume that the particle follows a geodesic and does not ...
Chandrahas's user avatar
  • 1,747
5 votes
1 answer
257 views

If two event horizons approach each other, can I observe the collision?

As Alice is approaching the event horizon, for outsider Bob, Bob will see that Alice's time delayed and slowly stop. I heard that even Bob waits for long time, Bob will never be able to see Alice ...
Saesun Kim's user avatar
2 votes
1 answer
89 views

Why do external observers see LIGO results if an object falling into a black hole never reaches the event horizon? [duplicate]

If I throw a clock towards a black hole, its time slows down, it is redshifted, and according to many theories it never reaches the event horizon from my point of view. How is it then, that a star can ...
Dean's user avatar
  • 123
0 votes
1 answer
378 views

About the LIGO result and Abhas Mitra [closed]

Well I read this article https://en.wikipedia.org/wiki/Abhas_Mitra and he has claimed that "The so-called massive Black Hole Candidates (BHCs) must be quasi-black holes rather than exact black holes" ...
Sidarth's user avatar
  • 997
5 votes
0 answers
36 views

How do we see an object fall into a Black hole in gravitational waves? [duplicate]

If an object emitting light falls into a black hole, the conventional wisdom is that an observer (at infinity) will never actually see it fall in - they will see it moving slower and slower as it ...
samgon's user avatar
  • 95
1 vote
0 answers
52 views

If event horizons (black holes) never form in a finite time, then how can they merge to create a common event horizon in a finite time? [duplicate]

There is another question about this topic, but that is asking about gravitational waves, and I am not. I am specifically asking about the timescale of the merger being finite (actually quick), ...
Árpád Szendrei's user avatar
1 vote
0 answers
31 views

Event Horizons and Events [duplicate]

How can two black holes with event horizons merge within the lifetime of the universe? Basically events are happening where events stop (to the outside observer) so does an event horizon actually ...
Kathmandu Gilman's user avatar