Crossing an event horizon

[Shag]

There is about a 50-50 split in what cosmologists think about spin. I'm the in belief that you can't actually say whether it spins or not, since I consider the EH out of the universe so it doesn't matter or have any effect one way or another. But! the matter around an EH is spinning quite fast. As fast as the core of a supermassive star spins (pulsar speeds). In fact some kinds of what were thought of as pulsars are in fact supermassive galactic black holes (Quasars). If a black hole takes alot of matter, the matter will be heated until it basically becomes a superheated plasma that gives off massive gamma rays, the black hole will then emit these as gamma ray bursts along its poles.

Its really pretty much as I said in my last post. Observer will see traveler slow and redshift and never quite touch the EH. Traveller will see the universe speed up and then as he touches the EH the universe ends. If traveler is immortal the only escape is the slim possibility that the BH bleeds out first through Hawking radiation.

 

[Bullgrit]

There are some unanswered questions of quantum effects - in a classical view, we out here would say they never reach the event horizon, Zeno's paradox style. However, quantum mechanics may provide a way for them to finally pop over the edge when we aren't looking.

Not to be snarky, but honestly asking: what is "infinite" in regards to black holes? If matter is falling through a black hole's event horizon, where time is supposedly frozen, how long is it taking the matter to move across the line?

Are the other "infinite" aspects of black holes (density, volume, etc.) also not really infinite?

Bullgrit

 

[Someone]

Not to be snarky, but honestly asking: what is "infinite" in regards to black holes? If matter is falling through a black hole's event horizon, where time is supposedly frozen, how long is it taking the matter to move across the line?

Are the other "infinite" aspects of black holes (density, volume, etc.) also not really infinite?

Bullgrit

The answer probably is some variation of "not yes or no, but something completely opposite of those" Honestly, when you start reading about quantum physics you realize that God was full of peyote when He created the universe.

 

[jonesy]

Not to be snarky, but honestly asking: what is "infinite" in regards to black holes? If matter is falling through a black hole's event horizon, where time is supposedly frozen, how long is it taking the matter to move across the line?

Are the other "infinite" aspects of black holes (density, volume, etc.) also not really infinite?

The volume is zero.

The density of the singularity is infinite because it is placed under infinite gravity which is caused by infinite curvature of spacetime. This means that inside the singularity space and time as we know them are effectively removed from the equation.

Every time that you'd move closer to the event horizon time would move slower. The closer you get, the slower you move. This is effectively a variation of Zeno's Paradox. You would need to be travelling at light speed to catch the singularity. The problem with that is that because you have mass your mass increases the closer you get to light speed, and the harder it becomes the closer you get.

The closer you get, the farther it seems.

 

[Shag]

Not sure why people arn't getting this very important point. You can never cross an event horizon, you can only ever slowly (from an outside observers POV) approach it. You have to remember that for something travelling at the speed of light there is no time. For a photon, the beginning and end of its journey are the same time.
I watch all kinds of shows on black holes and stuff and even the talking head scientists often get this wrong or at least oversimplify what they are saying and therfore give the wrong impression. There is a reason these guys are on TV and not in the lab. In talking to you Krauss and Tysen!

Lets go for a PS. There doesn't have to be infinities involved in any of this. The BH doesn't have to be infinetly dense just so dense its easier to say infinit. Time isn't infinit, its just until the end of the existence of this Brane, or until the BH bleeds out.

 

[Umbran]

There is about a 50-50 split in what cosmologists think about spin. I'm the in belief that you can't actually say whether it spins or not, since I consider the EH out of the universe so it doesn't matter or have any effect one way or another.

You should be able to actually say: if it has significant spin, the event horizon will not be perfectly spherical. Like planets, it should be be slightly "oblate" - a little pressed in at the poles of spin and fatter at the equator. At least so says the math.

Not to be snarky, but honestly asking: what is "infinite" in regards to black holes?

The density. The asymptotic slowing of clocks as you approach the event horizon.

If matter is falling through a black hole's event horizon, where time is supposedly frozen, how long is it taking the matter to move across the line?

Classically speaking: If you're out here in the rest of the fairly normal universe, it takes "forever". If you're the one falling, it takes as long as it would take you to fall, like you were falling anywhere else.

Quantum mechanically speaking: As above, but there might be a chance for you to "tunnel" through the event horizon at some point. The chance of you tunneling through should increase the closer you are to the horizon - and there's never certainty that you will pop across the barrier. So, maybe forever, maybe some absurdly long time.

Are the other "infinite" aspects of black holes (density, volume, etc.) also not really infinite?

Given that we've only ever observed these things at great distances, and don't have an adequate theory of how gravity and quantum mechanics work together, we cannot say with absolute surety. We can only speak by way of current understanding.

The BH doesn't have to be infinetly dense just so dense its easier to say infinit.

Actually, it does. If it isn't infinitely dense, if there is some force that does keep it from complete and utter collapse, you don't get an event horizon. Existence of such a force would imply the existence of something that can escape the grip of the object's gravity, and the hole is no longer "black".

Time isn't infinit, its just until the end of the existence of this Brane, or until the BH bleeds out.

This is why we often say, "until the end of time" - whatever end that might be. Mind you, brane theory is not tested (and so far is untestable) and not widely accepted - and depending what version you're talking about, our universe and our brane are not equivalent.

 

[Bullgrit]

So, crossing the event horizon will never happen, but it happens all the time.

Nothing can escape a black hole, but radiation is put off by it all the time.

I'm beginning to think black holes are just imaginary constructs scientists use to confuse the lesser minds. They're just a big inside joke among you smarty pants. ;-)

Bullgrit

 

[Umbran]

So, crossing the event horizon will never happen, but it happens all the time.

Generally speaking, we talk of things falling into a black hole, which is a protracted event. We only occasionally talk about things actually crossing the event horizon.

Nothing can escape a black hole, but radiation is put off by it all the time.

Matter that's falling in to a black hole tends to form an "accretion disk" - a whole bunch of stuff swirling around on its way down. As this dust and gas collects, it compresses and heats up, and emits radiation. This is the in-falling gas and dust, not the black hole itself.

The phenomenon of Hawking Radiation is also not actually the black hole radiating anything, so much as radiation from just outside the hole failing to fall in.

The black hole may radiate gravity waves if it is orbiting a star or some other large object.

I'm beginning to think black holes are just imaginary constructs scientists use to confuse the lesser minds. They're just a big inside joke among you smarty pants.

No. They just happen to be some of the more extreme objects out there. If you want everything to be simple and easily comprehensible to a brain developed for hunting and gathering... well, that's just too bad.

 

[jonesy]

I'm beginning to think black holes are just imaginary constructs...

That's pretty much what theoretical science is. The pursuit to discover a perfect model of how reality behaves.

The pursuit might not be realistically possible because of our limited perspective within reality itself, but even a slightly perfect model would be immensely useful.

Black holes are a good example of the attempt to make different fields of science connect with each other. If it would be possible to form a single model for black holes which works in both classical physics and quantum physics it would advance both branches by great leaps.

 

[El Mahdi]

...I'm beginning to think black holes are just imaginary constructs scientists use to confuse the lesser minds. They're just a big inside joke among you smarty pants...

If it's any consolation, Einstein would have probably agreed with you. He didn't believe that singularities were possible, and even wrote a paper attempting to prove this. I don't know if he ever changed his mind about this before his death, but there were a lot of aspects of quantum physics, including black holes, that he really didn't like.