Linked Questions

13
votes
5answers
7k views

How Are Galaxies Receding Faster Than Light Visible To Observers?

We know that some galaxies are moving away from us faster than the speed of light and we know it by measuring the redshift, but how's that possible? If they're moving away say at $2c$, how would the ...
12
votes
6answers
2k views

Does the radio (between two co-moving astronauts) stop working when crossing the event horizon?

There are a lot of questions about crossing the EH (event horizon) of a black hole on this site. Some of them suggest, that when you cross the horizon, nothing special happens, you don't even notice ...
2
votes
1answer
185 views

What do I see looking forward inside the black hole? [closed]

I have read this question: Future light cones inside black hole What happens to light that falls into a black hole? What would be the view like from inside a black hole looking towards the event ...
-1
votes
1answer
318 views

Do photon inside event horizon exceeds speed of light? [closed]

Event horizon is a region of space whereby nothing with information can escape, so I imagine that a photon falls into this region of space does it accelerates toward the singularity if it exists? Do ...
2
votes
3answers
111 views

Answering simple questions about black holes to someone not knowing GR

In the Newtonian description of a black hole, it is a gravitating astrophysical object for which the escape velocity exceeds the speed of light in vacuum ($c$). But what does this actually mean for a ...
109
votes
14answers
28k 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-...
13
votes
1answer
3k views

Would the inside of a black hole be like a giant mirror?

As any light reflected or emitted from objects inside a black hole (if it is possible to be there) does not leave the event horizon and comes back inside, would it be like seeing yourself? What I ...
3
votes
1answer
76 views

Would someone be able to see where they are headed once they crossed the event horizon? [duplicate]

Let us say an explorer was studying a supermassive black hole and ended up blundering past the event horizon. From my understanding, which may be wrong, the only paths allowed after crossing the event ...
16
votes
5answers
5k views

Will an object always fall at an infinite speed in a black hole? [duplicate]

Most of you if not everybody will agree that the stronger the gravitational pull, the faster an object will fall. For example, on a planet with 50 times the gravity of Earth, any object will hit the ...
40
votes
5answers
5k views

Why is a black hole black?

In general relativity (ignoring Hawking radiation), why is a black hole black? Why nothing, not even light, can escape from inside a black hole? To make the question simpler, say, why is a ...
2
votes
2answers
443 views

How does the speed of light vary throughout a black hole?

I surmise that there is no equation defining the speed of light, as there is with the speed of sound. Presumably, we assume that, at the event horizon, it falls to zero. What is its value at the ...
9
votes
5answers
908 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 ...
42
votes
4answers
13k views

Do virtual particles actually physically exist?

I have heard virtual particles pop in and out of existence all the time, most notable being the pairs that pop out beside black holes and while one gets pulled away. But wouldn't this actually violate ...
0
votes
2answers
410 views

Why doesn't the light get out?

You're standing on a gedanken planet holding a laser pointer straight up. The light doesn't curve round, or slow down as it ascends, or fall down. It goes straight up. Now I wave my magic gedanken ...
1
vote
3answers
331 views

What happens 'inside' the event horizon of a black hole, in particular to photon speed

This is a follow-up question to two answers given here and here, where the speed in different coordinate systems is discussed when approaching the Schwarzschild radius. To cite, derived directly from ...

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