All Questions
23
questions
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2
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Explanation about black holes
As a newbie I was reading the book "The Theory of Everything", and came about these two paragraphs which I just don't understand:
I had already discussed with Roger Penrose the idea of ...
- 41
24
votes
7
answers
8k
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Why light can't escape a black hole but can escape a star with same mass? [duplicate]
I'm new to astronomy and was wondering why light can't escape from a black hole but can escape from a star with the same mass. In theory, the gravity of a star 100x the mass of the sun, and the ...
- 341
1
vote
3
answers
153
views
Can I really see what is on the opposite side of a black hole?
This question is only about objects outside the event horizon. Both the observer and the object are just outside the event horizon.
I have read this question:
An observer can see the back side of the ...
- 29k
1
vote
1
answer
131
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In theory (because light can still enter a black hole) if you are inside of the event horizon, could you see outside of it? [duplicate]
To my limited knowledge, it should be possible for you to see from inside of a black hole. Is this true, or am I missing something?
5
votes
1
answer
348
views
When to rely on physical results derived using specific coordinates in GR?
I have been following a course on GR that at one point discusses the metric derived for the outside of a physical, non rotating uncharged massive object with spherical symmetry. For this situation I ...
- 73
0
votes
2
answers
541
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Why there are black holes that have a mass only 6 times the mass of the Sun?
We know that black holes are actually "black" because no light can escape them due to their gravity and that's why they appear black. That means the mass of the black hole most be extremely large even ...
- 117
5
votes
2
answers
199
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Would looking out from inside or near a black hole be unimaginably bright? [duplicate]
I have the following assumption based on limited knowledge.
A black hole appears dark to us because any light that would be emitted from it, and any light that passes nearby, is caught by the gravity ...
- 153
2
votes
2
answers
1k
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Do you see the outside world from inside the black hole (can you see past the horizon from inside it)? [duplicate]
I have read these questions:
If you fall in a black hole, when do you go past the event horizon?
Can matter really fall through an event horizon?
How can anything ever fall into a black hole as ...
- 29k
2
votes
0
answers
124
views
Could you actually see the event horizon of a Black Hole?
For years I thought to myself that surely you'd be able to see the event horizon of a Black Hole when looking at it against the surrounding light. I thought that it would be similar to this:
Where ...
- 21
0
votes
1
answer
159
views
Are black holes black?
GR was formulated before atomic clocks and radio signals between earth and space probes allowed actual measurements to be made.
Atomic clocks count a beat frequency, but the frequency of emitted ...
- 21
1
vote
1
answer
51
views
Does an event horizon happen abruptly, and if so, what would happen if I was floating in front of it and shined a flashlight in its general direction?
Does an event horizon happen abruptly, and if so, what would happen if I was floating in front of it and shined a flashlight in its general direction? Would it appear as if I was standing in front of ...
- 197
1
vote
1
answer
168
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What if you pointed a laser away from a black hole while falling into it?
Often this is asked if it was pointed towards a black hole. so I thought, if a scientist decided to sacrifice himself and jumped in a black hole, released some dry-ice mist and pointed a laser pointer ...
- 2,650
2
votes
1
answer
140
views
Would the event horizon of a black hole shrink as you approach?
While light cannot escape an event horizon, external light should still be observable from within. Would "entering" an event horizon cause it to apparently shrink away from you as you neared the ...
- 225
-2
votes
1
answer
154
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If photons do not have mass, why does light get attracted such that it cannot escape a black hole? [duplicate]
Does gravitational force of black hole attract the light? Or is it something else?
- 11
5
votes
3
answers
2k
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Is the event horizon of black holes visibly sharp, or blurry?
As you come in closer to a black hole, how do you see the event horizon? Is it always like a clear-cut surface? Or it only looks clear-cut from a distance, but as you come closer to the black hole, ...
- 185