Black Holes???

Hey guys, today in my "Intro to Astronomy" class we started talking about black holes, however i left the class with more questions than answers. At first, the teacher told us that (from Einstein) black holes were created by having enough mass in a sufficiently small space. and that there was an event horizon which determined the escape velocity being grater than that of the speed of light, therefore nothing could ever come out and thus making a singularity inside the black hole. However, the teacher then stated that (from Hawkins) these black holes would eventually "evaporate" . And i didnt understand, because i thought that even if just light enters the event horizon, wont it interact with mass and distribute momentum (because arent there experiments where they found photons acting like particles when coliding with other particles?? :-? :-?) and thus increasing the energy inside the black hole??... After class i went and talked to him and we had a great conversation about this topic, however im still completely confused as to how it happens... I started reading online about this and it just made it worse. I read that in the universe there can be thing called virtual particles that are created, these however, only exist for a relativistically short period of time. Because these "virtual particles" are a set of a particle and an antiparticle and once they appear they immediately destroy each other into a burst of energy... What i understood from my reading was that these particles can appear in the black hole, or at least one inside the event horizon and one outside, and when the antiparticle appears inside it collapses in destroying a particle already inside the black hole, and the particle appearing outside the event horizon becomes a real particle and shoots off and never gets "sucked in" thus reducing the size of the black hole... my question is, is nothing ever faster than the speed of light and does it apply to energy in every form, because if the antiparticle destroys a particle inside the black hole into a burst of energy, how does the energy leave the singularity, or the event horizon?

Any type of constructive feedback is appreciated

The antiparticle has negative energy and falls past the event horizon, actually reducing the amount of mass-energy inside. The real particle has positive energy and escapes into the Universe, increasing the mass-energy in the Universe. In this way the black hole shrinks and the mass-energy is redistributed back into the Universe. I think that Hawking also showed that the information trapped inside the black hole can be emitted in this manner, although certainly not in a useable form.

Justin said:

The antiparticle has [highlight]negative energy[/highlight] and falls past the event horizon, actually reducing the amount of mass-energy inside. The real particle has positive energy and escapes into the Universe, increasing the mass-energy in the Universe. In this way the black hole shrinks and the mass-energy is redistributed back into the Universe. I think that Hawking also showed that the information trapped inside the black hole can be emitted in this manner, although certainly not in a useable form.

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Does this mean that when it collides with a real particle inside the black hole it will annihilate it? and if so i thought you couldn't destroy energy.... and by having negative energy, then if i impose a symmetrically aligned coordinate system, wont the energy in the universe go to zero? is it ok to describe it that way??

If I remember correctly, virtual particles do not mess-up the conservation of mass/energy because they pop "out" of existence as quickly as they pop in. But when the pair gets separated by being on opposite sides of the event horizon, that forces it's twin in the "outside world" to become a "real" particle, instead of a fleeting virtual one. The energy for this particle has to come from somewhere, so it is debited from the mass/energy of the black hole that ate it's twin, kinda like a withdrawal from it's Paypal acct!

escape velocity being grater than that of the speed of light

Click to expand...

Actually, I believe the more accurate way of looking at this is that space-time is so warped that there is no path that will lead out of the event horizon - every path curves you back in!

my question is, is nothing ever faster than the speed of light...

Click to expand...

Actually, I believe the theory prevents a particle from "crossing" the lightspeed threshhold, i.e. - going from subluminal to superluminal speeds. From what I've been told, there is nothing in Einstein's theories that prevents a particle from traveling faster than light (i.e. - the theoretical "tachyon" particle, which can travel faster than light, it just can't go any slower!)

Also, remember that this speed limit applies to particles moving through space. There is no such FTL "speed limit" for how fast the fabric of space itself can move! For example, I believe during the "inflationary period", the universe is thought to have expanded much faster than lightspeed! This also explains why there is a limit on the "observable" universe, and why we cannot see galaxies that exist beyond it. This "no speed limit for space itself" is also the basis for the hypothetical "warp" drive.

...and does it apply to energy in every form...

Click to expand...

There is also the very interesting "quantum entanglement", in which an entangled particle is somehow able to communicate it's state to it's twin instantaneously over any distance! Scientists are still scratching their heads trying to figure-out exactly how this happens - some have speculated a magical faster-than-light particle is exchanged between the two, another theory has it that the particles actually communicate with each other backwards in time to the point where they first became entangled!

Quantum Physics can be a real mind-blower at times!

It is only mini black holes that are subject to "evaporation" as you put it. Mini black holes are created in our atmosphere many many times daily because of cosmic radiation. They last a few microseconds and disappear, emiting light.

Stellar mass or super massive black holes do not display this behavior.

This topic is beyond the level of anyone on the forum I'm afraid. Astrophysics is so complicated it's beyond mind boggling. Another issue is that new theories are constantly created as science continues to advance. All I can tell you about a black a hole is that it's a tear in space and time. Only guesses beyond that, black holes were only recently even proven to exist. Don't forget white holes either. http://en.wikipedia.org/wiki/White_hole. Now remember all of that has math behind it. Endless equations. String theory is even stranger.

Already created a thread about black holes + antimatter



Never enough discussion about this awesome topic, though!

Go on...

laser83 said:

This topic is beyond the level of anyone on the forum I'm afraid. Astrophysics is so complicated it's beyond mind boggling. Another issue is that new theories are constantly created as science continues to advance. All I can tell you about a black a hole is that it's a tear in space and time. Only guesses beyond that, black holes were only recently even proven to exist. Don't forget white holes either. http://en.wikipedia.org/wiki/White_hole. Now remember all of that has math behind it. Endless equations. String theory is even stranger.

Click to expand...

True to every word, we may never really gain a true understanding of it...ain't it great?

seoguy said:

If I remember correctly, virtual particles do not mess-up the conservation of mass/energy because they pop "out" of existence as quickly as they pop in.  But when the pair gets separated by being on opposite sides of the event horizon, that forces it's twin in the "outside world" to become a "real" particle, instead of a fleeting virtual one.  The energy for this particle has to come from somewhere, so it is debited from the mass/energy of the black hole that ate it's twin, kinda like a withdrawal from it's Paypal acct!

escape velocity being grater than that of the speed of light

Click to expand...

[highlight]
Actually, I believe the more accurate way of looking at this is that space-time is so warped that there is no path that will lead out of the event horizon - every path curves you back in![/highlight]

my question is, is nothing ever faster than the speed of light...

Click to expand...

Actually, I believe the theory prevents a particle from "crossing" the lightspeed threshhold, i.e. - going from subluminal to superluminal speeds.  From what I've been told, there is nothing in Einstein's theories that prevents a particle from traveling faster than light (i.e. - the theoretical "tachyon" particle, which can travel faster than light, it just can't go any slower!)

Also, remember that this speed limit applies to particles moving through space.  There is no such FTL "speed limit" for how fast the fabric of space itself can move!  For example, I believe during the "inflationary period", the universe is thought to have expanded much faster than lightspeed!  This also explains why there is a limit on the "observable" universe, and why we cannot see galaxies that exist beyond it.  This "no speed limit for space itself" is also the basis for the hypothetical "warp" drive.  

...and does it apply to energy in every form...

Click to expand...

There is also the very interesting "quantum entanglement", in which an entangled particle is somehow able to communicate it's state to it's twin instantaneously over any distance!  Scientists are still scratching their heads trying to figure-out exactly how this happens - some have speculated a magical faster-than-light particle is exchanged between the two, another theory has it that the particles actually communicate with each other backwards in time to the point where they first became entangled!

Quantum Physics can be a real mind-blower at times!

Click to expand...

wow, never though of it that way! ......BUt wouldnt you have a discontinuity in the first place, so how would a particle even go through the event horizon if there is no space-time to travel through???
... and thanks guys for all the responses, i thought the post was just gonna die after 2  

laser83 said:

[highlight]This topic is beyond the level of anyone on the forum[/highlight] I'm afraid. Astrophysics is so complicated it's beyond mind boggling. Another issue is that new theories are constantly created as science continues to advance. All I can tell you about a black a hole is that it's a tear in space and time. Only guesses beyond that, black holes were only recently even proven to exist. [highlight]Don't forget white holes either[/highlight]. http://en.wikipedia.org/wiki/White_hole. Now remember all of that has math behind it. Endless equations. String theory is even stranger.

Click to expand...

I thought white holes was the "other end of a black hole" that is, if a black whole appeared here (in this universe or dimension) everything it sucked in would be emptied out in another universe, per say, and thats what was seen as a white hole. however i thought Hawkins stated that black holes diminished IN this universe and that they were not "portals" to others therefore whiteholes shouldnt exist


And it never hurts to brain storm, plus there is still a difference in what everyone knows about this topic in this forum, so im sure a lot of ppl will learn new things! ... like ME! ;D

Niko said:

Already created a thread about black holes + antimatter



Never enough discussion about this awesome topic, though!

Go on...

Click to expand...

I LIKE UR STYLE HAHAHA

Nothing wrong with discussing it.   Only point is even the geniuses that make the theories don't really have clue; no one does. Professor Michio Kaku is my favorite lecturer on theoretical physics. He manages to dumb it down enough where it can make sense to average people. http://www.youtube.com/watch?v=ZnQLsERqTIg Very good series to watch. though not on black holes.

Imagine the idea of a Mutliverse instead...That's right, his theory is that there are an infinite number of universes and each is in its own sort of bubble. I thought that was kid's cartoon stuff. Unreal.

.... yeah i looked at the youtube videos that stuff seems much harder than black holes though lol!

.... Look what i found ( http://www.youtube.com/watch?v=0Hmv-6qLM8Y ), its supposed to be evidence that black holes exist. apparently the mass that makes these stars move like that is about 4 million times that of our sun, and for it to be in a such small space, the only explanation now is that it is a black hole. I think you can calculate the radius that a certain mass needs to be compressed to, to create a black hole by using the Schwarzschild radius formula... we did this in class for the sun and it was something like 3 km while the earth was only like 9 milimeters!!!



BTW this is an incorrect aproximation

I like the idea of wormholes best. The energy required to create and maintain one would be equal to the output of the sun as I recall but in theory it could be done. The sad part is I'd like one best for traveling quickly to Japan or Germany for example by walking through a door. I know they are always used for spaceships in sci-fi but why not make my traveling easier on earth first.  ;D

For exact numbers on a black hole you can calculate it but it's enough to imagine it took a mass the size of a red giant star going supernova to create one. All that mass creates a small sized tear in space that has unlimited mass as I understand.

When that particle accelerator in Frace/switerland is fixed you'll be able to see a black hole for yourself right on Earth!   That's a joke to be clear. The people afraid of the large hadron collider are just paranoid.

laser83 said:

I like the idea of wormholes best. The energy required to create and maintain one would be equal to the output of the sun as I recall but in theory it could be done. The sad part is I'd like one best for traveling quickly to Japan or Germany for example by walking through a door. I know they are always used for spaceships in sci-fi but why not make my traveling easier on earth first.  ;D

For exact numbers on a black hole you can calculate it but it's enough to imagine it took a mass the size of a red giant star going supernova to create one. All that mass creates a small sized tear in space that has unlimited mass as I understand.

When that particle accelerator in Frace/switerland is fixed you'll be able to see a black hole for yourself right on Earth!   [highlight]That's a joke to be clear.[/highlight] The people afraid of the large hadron collider are just paranoid.

Click to expand...

But its not, theoretically... acording to Hawkins there will (should) be creations of black holes but they are going to be extreamlly small, and they will "evaporate" almost instantaneously... there is (or supposed to be) small black holes created in our outer atmosphere all the time from gamma rays and such, that strike the atmosphere with more energy even than that produced in the LHC but they are still very small that they brake down really fast... Apparently all black holes deteriorate too. Just that it takes the big ones a lot more time.