Speed of Light question

[Harmon]

Okay, so all the matter that enters a black hole incleases the size of the BH(?), which increases its strength(?)- now, my new question is- what happens to that energy/the stuff that fell into the black hole, what happens to it?

Do all black holes eventually fall together (billions, perhaps trillions of years from now), making one supper massive black hole that has nothing left to "eat". What happens now? (Not that anyone would care, that the black hole is alone in the multiverse.) Does the BH explode throwing all its energy out into a new universe? Does it just sit there sucking up the nothingness of an empty void?


A follow up question-
What about the idea that eventually a black hole will have so much crap flowing around it, that nothing or very little can get into the BH because everything is "plugging up the drain"; nothing can get closer because everthing is bumping into each other.

Sorry, guys when I can't sleep my mind wonders.

 

[Umbran]

now, my new question is- what happens to that energy/the stuff that fell into the black hole, what happens to it?

It falls in towards the singularity at the center. There are no stable orbits inside the event horizon. It may take a while, but eventually, everything reaches the singularity.

Whatever may have happened at the event horizon, the tides near the singularity are enough to shred anything. And physical object gets shreded down to it's consituant particles before it actually reaches the singularity.

What happens at the singularity? Nobody knows. This is the place where everything we know breaks down. We have no reliable prediction.

There are some edge cases - I believe it's for spinning black holes - there are paths within the hole that don't lead to the singularity, but instead lead into other "spaces" - this is where the old story about going into a black hole and coming out in another universe comes from. I'd have to look at my notes, but I don't recall these spaces can be reached by anything in "free fall".

Do all black holes eventually fall together (billions, perhaps trillions of years from now), making one supper massive black hole that has nothing left to "eat". What happens now? [/qutoe]

Well, remember that even if every scrap of matter in the Universe has been eaten, the space itself isn't sitting aroudn doing nothing. Right now, our Universe is still expanding. If it continues, the holes may not ever coalese into one megahole, because they'll be too far apart. On the other end of the scale, if the Universe comes to a "Big Crunch", what happens to the black holes becomes moot, because the universe squeezes down to a singularity itself.

(Not that anyone would care, that the black hole is alone in the multiverse.) Does the BH explode throwing all its energy out into a new universe? Does it just sit there sucking up the nothingness of an empty void?

It doesn't just sit there sucking up the nohting ness. Black holes do not suck. Things fall into them. There's a subtle difference. If nothing falls in, they just sit there, doing nothing at all.

Note that Mr. Hawking has theorized that black holes can "evaporate". In an odd turn of quantum mechanics, pairs of particles can be created near the event horizon. If one manages to escape, the other falls into the black hole.

That means there's extra mass/energy in our universe, and that has to come from somewhere. So, to balance the scales, the black hole loses mass. If this goes on long enough, the black hole can evaporate. Of course, for any but the tiniest of holes,this process is excrutiatingly slow. At the end, there is a sort of explosion into the void.

A follow up question-
What about the idea that eventually a black hole will have so much crap flowing around it, that nothing or very little can get into the BH because everything is "plugging up the drain"; nothing can get closer because everthing is bumping into each other.

Not bloody likely. To have that, all the "plugging" matter would have to be in stable orbits around the hole, and not fall out of stable orbits when new matter falls in and hits it. I am not sure this is even mathematically possible, much less likely in a practical sense.

 

[Harmon]

Mr Hawking said that BHs can "evaporate" - whow! Hold up, if those particals kinda drift back out of the BH, bleeding off wouldn't the BH suck them back in?

Is it my understanding that black holes don't rotate? Did I understand that right? It was my understanding that most things rotate in an unstable orbit or when something effects them in a not so predictable way (say our moon, which doesn't rotate on its axis but does wround the Earth, and Pluto and its moon rotate around a central point- they always face each other). Shouldn't a BH rotate because of the unpredictable matter that is coming at it?

Something else- the area between the singularity and where we can still see light, that area is called the Event Horizon (right?), so what happens to the light that enters that area. If what I think is true its where the light speeds to past a speed that we can perceive, past the speed of light (which according to what I understand (which admittedly isn't much)) is not possible by all that I have read here.

Sorry, I feel like I am asking questions you have already gone over and I am just not getting through my thick skull. Again, another thank you for your time and patience.

 

[Umbran]

Mr Hawking said that BHs can "evaporate" - whow! Hold up, if those particals kinda drift back out of the BH, bleeding off wouldn't the BH suck them back in?

It isn't "drifiting out" of the hole.

In QM, a particle-antiparticle pair can be created out of nothingness for a short time. Generally, they fly apart and come back together in the smallest fraction of a second, annihilate each other, and are gone, and the Universe is none the wiser.

When this happens just outside the black hole, you can have the problem that occasionally, they'll fly apart - and one of them will go across the Event Horizon, and the other won't. It doesn't fall into the hole, and it doesn't annihilate with it's partner. It just flies off into space, as if teh hole had emitted it.

Is it my understanding that black holes don't rotate? Did I understand that right? It was my understanding that most things rotate in an unstable orbit or when something effects them in a not so predictable way (say our moon, which doesn't rotate on its axis but does wround the Earth, and Pluto and its moon rotate around a central point- they always face each other). Shouldn't a BH rotate because of the unpredictable matter that is coming at it?

Do not confuse "spin" with "orbit". A top spins aroudn it's axis. The Earth spins on its axis to produce day and night. The Earth also orbits around the Sun. Rotation and orbiting are two separate things.

Our moon does spin. The moon is what we call "tidally locked" - it has a period of spin exactly one monthlong, so that it always has one side facing us.

A black hole may rotate because the star from which it formed rotated. Our Universe likes to conserve angular momentum, so spinning things tend to keep spinning unless somethign slows them down. There's nothing in the process of becoming a black hole that would eliminate spin - so, if the star was spinning before it went supernova, the resulting black hole will also spin. Spin has little to do with "unpredictability".

Something else- the area between the singularity and where we can still see light, that area is called the Event Horizon (right?)

You can imagine a black hole as a balloon, with a dot down in it's center. The "singularity" is a mathematical point at the very center of the black hole. The "event horizon" is the surface of a sphere around the singularity. From within the sphere, no light can ever hope to escape to the rest of the Universe - so that sphere will appear black. We can see nothing within the hole at all.

so what happens to the light that enters that area. If what I think is true its where the light speeds to past a speed that we can perceive, past the speed of light (which according to what I understand (which admittedly isn't much)) is not possible by all that I have read here.

Like everything else, light that finds itself within the event horizon can never escape again. It has only one way to go - down to the singularity. It can take its time getting there, but eventually, it must go to the center.

Now, to be honest, nobody can truly say what goes on inside the event horizon. Because no signal can ever get out of the hole, we can't get a picture of what happens inside. But there's no reason to think that the light speeds up as if falls inwards. The basic laws of physics still hold for most of the way down to the signularity. Only very, very close to the mathematical point do we lose grasp of what goes on.

About light - one can consider it this way:
If a thing has mass, it can have energy associated with it's motion, called kinetic energy. The kineic energy of an object is 1/2 * M * V^2 (one half times it's mass times the square of it's velocity). An object with mass can gain or lose energy by speeding up or slowing down.

Light has no mass. I has a kinetic energy of zero, always. It cannot gain energy by speeding up, nor lose energy by slowing down. If it has to change energy, it has to do it some other way (usually by changing frequency).

Now, here's the rub - if light could speed up or slow down, you wouldn't have black holes. The base assumptions that lead to the existance of black holes include the speed of light being a constant.

 

[ssampier]

*blinks*

...

*scratches head*

....

Anyone else lost as I am?

Any primers for us non-scientist/physics majors? Keep in mind my grasp of physics can be summed up in Newtonian physics. Anything more and my head explodes.

Actually, that isn't accurate. I saw the movie EVENT HORIZON, and the spaceship is clearly sucked into the dimensional vortex at the film's end. No escape.

Of course, they ended up in a different dimension (HELL, if you're wondering). I think the movie was neat until that was revealed.

 

[Umbran]

Any primers for us non-scientist/physics majors? Keep in mind my grasp of physics can be summed up in Newtonian physics. Anything more and my head explodes.

And these posts certainly wouldn't be my choice for trying to teach this stuff, either. Remember that entire college courses and books can be done on this topic. Addressing questions in a haphazard way, without any visual aids, is certianly going to be disjointed.

You want a primer that's good for folks without the background? Stephen Hawking's A Brief History of Time covers the basics. I think it has all of one equation in it. Theory developed after that book was written is coverred in The Universe in a Nutshell.

 

[physicscarp]

In addition to A Brief History of Time, which is the book that drove me to be a physicist, I'd recommend The Elegant Universe by Brian Greene. The first five chapters of the book provide, IMO, the best layperson description of special/general relativity and quantum mechanics. His prose is easy to read, and he makes sure to describe both the common misconceptions that might be held by the reader, as well as the actual nature of the theories.

Moving beyond those first chapters takes you into new territory (string theory), but it still remains interesting.

 

[Harmon]

Stephen Hawking's A Brief History of Time ..... The Universe in a Nutshell.

Read the first, have to check out the second. Its pretty heady stuff (probably why I can't get it through my head), but its always been something that has interested me.

Umbran is doing a fair job in a really bad medium. Its hard to explain this stuff and for your questions to be understood.

 

[fuindordm]

Do all black holes eventually fall together (billions, perhaps trillions of years from now), making one supper massive black hole that has nothing left to "eat". What happens now? (Not that anyone would care, that the black hole is alone in the multiverse.) Does the BH explode throwing all its energy out into a new universe? Does it just sit there sucking up the nothingness of an empty void?

That depends on what the universe is doing. The biggest black holes are in the center of galaxies, and its conceivable that over trillions of years such a hole could swallow the whole galaxy. (Probably longer; more likely it would swallow the core, then every billion years or so interactions between the stars in the outer regions would send a star drifting close enough to the center to get eaten as well.)

Meanwhile, however, the universe is expanding and the galaxies are getting farther apart. According to the current state of affairs, the expansion of the universe is accelerating, and rather than one big black hole we'll eventually end up with a universe consisting of nothing but black holes, but these getting farther and farther apart forever.

Some older models of the universe predicted a collapse, in which case all the black holes would get closer and closer and absorb each other. These models weren't supported by observations, though.

Ben

 

[glass]

Umbran is doing a fair job in a really bad medium.

Seconded.


glass.