black holes FAQ are there on my website also
http://www.exploreuniverse.com/ic

__________________
"We have to explore n explore"
http://www.exploreuniverse.com

I asked if you would die i you went into a black hol on another website that was a FAQ site about black holes anyway they said that you would die before even getting close but you would have to be close enoughf to feel the gravity.

I'm told you would die, because of tidal stretching, before you get to the event horizon of the black hole. Note this is to be distinguished from the usual curvature of spacetime that happens just because there is a gravity-- we are talking about additional monkeying due to the way gravity is changing, and that is what would be fatal.

It depends on the size of the black hole. Look here.

__________________
"All your bias are belong to us." Ara Pacis
"A witty saying proves nothing." Voltaire

Hi everyone, I am new so if my questions are over asked already, just let me know, I read about 8 pages of this thread and found nothing of my question, so here goes....


Suppose the our galaxy and Andromeda both had black holes near the center and collided, what would the black holes do to each other? Would they still be separated, or would they suck each other together in a vary cataclysmic outcome? I know this is completely imposable to know, but any ideas?

Thanks in advance, DS

Hi, Dragon Star. Try doing a forum search for 'black holes galaxies collide', or something of that sort. You should find a few threads that discuss that scenario.

__________________
"All your bias are belong to us." Ara Pacis
"A witty saying proves nothing." Voltaire

OK, thank you for the info.

The reason I didn't try a search is my other forms I go to has the search function down, so I am used to just asking the question, sorry for clutter.

FYI, I just tried that search and only got two hits, both in ATM. I don't think that's going to be very helpful. This is of course not a hypothetical question, galaxies harbor black holes and they do collide. But there wouldn't seem to be any reason for the black holes to approach close enough to coalesce-- remember that the gravity of a galaxy if from dark matter, and black holes are a small contributor in most cases.

I have a question which I frequently ask about black holes, though no one else seems to:

If any observer at any fixed distance outside a given event horizon, observes that it takes forever (literally) for another object to fall into the horizon (yes, yes, I know for the infalling object the proper time is finite! That's not the point.) The point is that infalling matter into a black hole never gets inside the black hole in a finite amount of time with respect to anywhere in the outside universe.

So how does a black hole end up gaining mass? How can the event horizon ever expand from a zero radius if nothing can end up crossing one in a finite period of time (wrt distant observer)? Furthermore (as a mental model), if you have an array of mass particles, how can these mass particles merge to form a larger black hole when time dialation would prevent them from crossing their mutual event horizons?

Thank your for your time and comment, I also got very few hits and they had little info. It nice to be able to use the search function though...Can't on my other boards.


Edit, I fould some interesting simulation videos on galaxy colision, find it HERE

I've puzzled about this too, and don't have a definitive answer, but I think the answer may be that a bunch of mass clustered at the edge of a still-forming event horizon looks a lot like a normal event horizon from any considerable distance away. The gravity is doing the same things, and you don't get much light escaping anyway, so you may as well call it a black hole and be done with it. It's sort of like treating stars as spheres-- it's not formally correct, but usually works fine for most applications. Remember, everything in science is an idealization! Science is the art of using observations to select between idealizations, we should not be bothered when our idealizations don't formally exist in our reference frame.
But yes, I think it's true that black holes don't "really" exist, except possibly for ones that existed from the Big Bang itself.

Guys, that question was answered on the previous page.

__________________
"All your bias are belong to us." Ara Pacis
"A witty saying proves nothing." Voltaire

Oops. I guess others have had the same question. I wasn't paying attention to the thread content. Sorry.

(seemed easier just to say it again, but you're right, the useful links are on the last page.)

Here's a question: can it be determined if a black hole is matter or antimatter, or both? And what impact does the answer have on Hawking radiation, i.e., are black holes a source of antiparticles?

Matter and Antimatter Black Holes

As for antiparticles, I guess you would need to take a sample from the jets exiting the black hole, but I don't think this is an easy task, any volunteers?

Thanks for the link, though it certainly seems like an ATM idea that supermassive black holes in galaxies bridge to nearby white holes whose impact is seen. And I'm still a bit confused if they are saying that an antimatter black hole is a white hole, since antimatter is matter going backward in time. But both matter and antimatter would fall into a black hole, so it still leaves me very unclear.

White Holes are completely hypothetical, as they defy the Second law of thermodynamics. But a white hole is only the opposite of a black hole, and would spew out matter and energy into space, but, immensely dense objects spewn out by the white hole would pull each other back inward because of their large gravity. This would make the white hole collapse into a black hole. Again, all of this is hypothetical, but it seems the way it would happen.

Uhm...I would think that there is no difference between the two, In fact, if I should hazard a guess, I would think the singularity consists of neither, as any mass that makes up the singularity is likely to be compressed well beyond the neutron and quark stages, and the difference between matter and anti-matter is in the way the atoms is built...

__________________
Game over, you lose, we hope you enjoyed playing the exciting game of Thermodynamics...

The only things that can be determined about black holes are their mass, charge, and spin.

None at all.

__________________
Some try to tell me, thoughts they cannot defend,... - Moody Blues.

Re: do black holes ever actually form?

Newborn black holes

__________________
"All your bias are belong to us." Ara Pacis
"A witty saying proves nothing." Voltaire