[ 3 / biz / cgl / ck / diy / fa / ic / jp / lit / sci / vr / vt ] [ index / top / reports ] [ become a patron ] [ status ]
2023-11: Warosu is now out of extended maintenance.

/sci/ - Science & Math

View post   
File: 994 KB, 232x227, lightning.gif [View same] [iqdb] [saucenao] [google]
4502706 No.4502706 [Reply] [Original]

/sci/, after drunken discussion with a friend, he raised a point about black holes which I couldn't answer.
If space is expanding, surely something that is (just) inside the event horizon could escape it as space is created between the black hole and the EH?
Is there something obvious that's being missed here?

>> No.4502714

>>4502706
the event horizon is expanding as well

>> No.4502713

Full tart.

Space expanding is only measured by objects moving further away from each other.

>> No.4502726

>>4502714
That implies that the gravitational pull is increasing though, surely? And the black hole isn't gaining mass.

>> No.4502736

I don't know much about this, but I believe that everything remains relative to each other as space expands. Seperate objects within space don't actually move away from each other.

>> No.4502742

>>4502736
Galactic redshift...

This is obviously far far into the hypothetical spectrum here, but I find it interesting. As I've said, I'm almost certainly just missing something fairly basic, but I don't know what it is. And I don't see how the event horizon could also be expanding.

>>4502713
That's my point. If it is moving away from the singularity, then surely it will pass the event horizon.

>> No.4502745

The expansion is galaxies moving away from other galaxies, not everything moving away from everything.

>> No.4502753

>>4502745
Why does it not happen on a smaller scale?
What's special about intergalactic space?
(Not just that it's very big)
What does the universe define as a galaxy...

>> No.4502762
File: 126 KB, 1100x914, 1325014814640.jpg [View same] [iqdb] [saucenao] [google]
4502762

>>4502726
>black holes doesn't gain mass.

>> No.4502764

I don't know anything about this stuff, but I think space in black holes is curved in on itself. If space were to expand inside a black hole, it would only expand within the black hole and not cross the event horizon.

>> No.4502769

>>4502762
No. THIS black hole isn't gaining mass, as nothing is falling into it. Seriously.

>> No.4502785

>>4502764
Hmmm. Maybe.

>> No.4502789

>>4502745
Actually in perspective, everything is moving away from everything.

>> No.4502799

If space is expanding, why aren't you getting fatter every day. Check mate atheists.

>> No.4502814

>>4502762
The hell is that a picture of?

>> No.4502821

Space is not expanding at anywhere near the rate to cause anything to escape the edge of the event horizon.

Might become an interesting issue if metric expansion continues to increase indefinitely. However, black holes will probably have evaporated by then.

>> No.4502848

>>4502706
Nope.

If you use the schwarzschild metric (black-holes), even with expansion incorperated, YOU WILL NOT GET WHAT YOU ARE TALKING ABOUT.

This is a basic Grad Level GR question, and requires a shit-ton of math and physics pre-rec's.

>> No.4502858

>>4502848
Fair enough; is there a specific name for this that I can search for to get more information?

>> No.4502905

>>4502858
Not that I recall.

What you want is a cross between Schwarzschild and the FLR metric. The problem is to get one that is actually a solution to the problem (einsteins equations).

I think you just have to use pertubration theory on the Scharzchild metric to introduce a "a(t)", that represents the expansion of space. The whole thing gets very fucking messy though.

Most high level physics like this becomes "unsolvable" algebraically. It becames alot of perturbation and numerical analysis.

The expansion of space is many many many many orders less then the collapse of a body (black-hole), this is why it is never even taken into account in problems like this. Also, the Schwarzchild metric also implies the existance of white-holes, and possible worm-holes (although it is almost impossible to keep them open).

In short the answer is no, matter in the black-hole cannot escape. However, new matter can "appear" just outside the event horizon (and it does).

>> No.4502913

What the hell is with OPs pic? How the fuck does that happen?

>> No.4502931

>>4502913
Because it's fucking awesome, that's why.

>>4502905
I understand matter can't escape, which is why I was confused with the question. Thanks for answering, though.

>> No.4502932

>>4502905
The fuck is a white hole?

>> No.4502948
File: 15 KB, 400x286, 0500_eazy_e_a.jpg [View same] [iqdb] [saucenao] [google]
4502948

>>4502931
Black-holes/White-holes/Worm-Holes actually fuck up the space in a way unlike anything else. It isn't just the standard strech, bend, it is actually fucking torn.

This "torn" space, does not necessarily need to obey the rules of space expansion (external space). Fucked up space (internal space) acts with its own unique rules, that supercede all other rules.

When you actually do the physics with the schwarzschild metric you will divide space into the "exterior" regular regions, and the fucked up "interior" regions. The exterior regions obey most of what we expect, the interior regions are fucking strange and are still under investigation. It is known though that they don't behave anything like regular space.

>> No.4502953

>>4502913
thats normal lighting, just in super-slow mo.

>> No.4502967
File: 126 KB, 1024x768, professor-frink.gif [View same] [iqdb] [saucenao] [google]
4502967

>>4502932
http://en.wikipedia.org/wiki/White_hole

It is pretty much the opposite of a black hole. The ultimate fucking emitter. It is impossible to travel into a white-holes event horizion. It is always spewing shit out into normal space.

It appears in the exact same theory that gives the blackhole, although we never observed just a "white-hole".

We do now have evidence of black-holes, that also spew shit out though. Happens all the fucking time. It is now thought that the black-hole and white-hole can exist as the same object. What we "see" is the black hole, that "makes" particles on the event horizion.

So we see "mixtures" of black-holes and white-holes. According to Steven Hawking, all black-holes are actually white-holes as well, it is just a matter of perpective.

>> No.4502969

>>4502967
>>4502967
In quantum mechanics, the black hole emits Hawking radiation, and so can come to thermal equilibrium with a gas of radiation. Since a thermal equilibrium state is time reversal invariant, Stephen Hawking argued that the time reverse of a black hole in thermal equilibrium is again a black hole in thermal equilibrium.[2] This implies that black holes and white holes are the same object. The Hawking radiation from an ordinary black hole is then identified with the white hole emission. Hawking's semi-classical argument is reproduced in a quantum mechanical AdS/CFT treatment,[3] where a black hole in anti-de Sitter space is described by a thermal gas in a gauge theory, whose time reversal is the same as itself.

>> No.4502986

>>4502967
Could you translate that to math for me? I know that a black hole arises when your schwarzschild metric blows up at singularities, what's going on with a white hole then?