Tell me what you know about Black holes

[Last Conformist]

You're misremembering (or possibly misunderstanding) Hawking. Antimatter has positive mass, which means a black hole grows when it swallows it.

The photon is it's own antiparticle, BTW.

[KrazyHorse]

Originally posted by Proteus_MST


And it gets smaller when it consumes Antimatter.

BZZZZZTTTTT

WROOOONNNNGGGG

[Spec]

if it grows non-stop, than surely it will consume the whole universe someday or another...Its only logical.

Unless I am misunderstanding...

Spec.

[Spec]

Originally posted by KrazyHorse


BZZZZZTTTTT

WROOOONNNNGGGG

Can you answer my questions KH? No sarcasm. Honest question.

Spec.

[KrazyHorse]

Originally posted by Spec
if it grows non-stop, than surely it will consume the whole universe someday or another...Its only logical.

Unless I am misunderstanding...

Spec.

Not necessarily. The rate of growth depends on the surrounding density of matter available to be sucked in.

[KrazyHorse]

Originally posted by Proteus_MST
In the chapter about the mechanisms that lead to the shrinking of (theoretical) primordial black holes.

Hawking radiation has nothing to do with the accretion of antimatter.

[Proteus_MST]

Originally posted by KrazyHorse


BZZZZZTTTTT

WROOOONNNNGGGG

So, as you´re probably the person best suited for explaining Hawking radiation and evaporating primordial black holes, do so.
Especially, where I got it wrong.

[Spec]

Every thing moves in the universe, iirc. So, the way I see it, everything is bound to end-up close to a black hole on day or another since it sucks everything in, right?

What would happen if 2 black holes collide? Can that happen anyhow?

Sorry, I know nothing about this.

Spec.

[KrazyHorse]

Go look up Hawking radiation on wikipedia. Without a background in general relativity and QFT this is as much understanding as you're going to be able to get, no matter what the source.

[Spec]

Me?

Spec.

[KrazyHorse]

Originally posted by Spec
Every thing moves in the universe, iirc. So, the way I see it, everything is bound to end-up close to a black hole on day or another since it sucks everything in, right?

It's not bound to do anything. It can continue to collect mass for an infinite amount of time and yet have its mass remain finite.

Whether or not all the matter in the universe would eventually end up in black holes is a tricky question. You actually have to simulate the evolution of large scale structure and the growth of black holes to see what happens. This behaviour is not inherently obvious from first principles as far as I can tell.

[KrazyHorse]

Originally posted by Spec
Me?

Spec.

Proteus

[Spec]

In physics, Hawking radiation (also known as Bekenstein-Hawking radiation) is a thermal radiation thought to be emitted by black holes due to quantum effects. It is named after British physicist Stephen Hawking who worked out the theoretical argument for its existence in 1974, and sometimes also after the Israeli physicist Jacob Bekenstein who predicted that black holes should have thermal properties. Because Hawking radiation allows black holes to lose mass, black holes which lose more matter than they gain through other means, are expected to evaporate, and shrink, and ultimately vanish. Smaller 'micro' black holes are currently predicted by theory to be larger net emitters of radiation than larger black holes, and to shrink and evaporate faster.

For everyone to see.

Spec.

[KrazyHorse]

Originally posted by Spec

What would happen if 2 black holes collide? Can that happen anyhow?

Not just can it happen, but I spent an hour or so talking to a woman who spends her time simulating these collisions on a computer yesterday.

These collisions are going to be a major source of gravitational waves which should be detected by LISA if and when it ever flies.

[KrazyHorse]

Originally posted by Spec


For everyone to see.

Spec.

You missed the important bit.

Black holes are sites of immense gravitational attraction into which surrounding matter is drawn by gravitational forces. Classically, the gravitation is so powerful that nothing, not even radiation or light can escape from the black hole (it is black because no light can leave it). It is yet unknown how gravity can be incorporated into quantum mechanics, but nevertheless far from the black hole the gravitational effects can be weak enough so that calculations can be reliably performed, in the framework of quantum field theory in curved spacetime. Hawking showed that quantum effects allow black holes to emit exact black body radiation, which is the average thermal radiation emitted by an idealized thermal source known as a black body. The radiation is as if it is emitted by a black body of temperature which is related (inverse proportional) to the black hole mass.

Physical insight on the process may be gained by imagining that particle-antiparticle radiation is emitted from just beyond the event horizon. This radiation does not come directly from the black hole itself, but rather is a result of virtual particles being "boosted" by the black hole's gravitation into becoming real particles.

A more precise, but still much simplified view of the process is that vacuum fluctuations cause a particle-antiparticle pair to appear close to the event horizon of a black hole. One of the pair falls into the black hole whilst the other escapes. In order to preserve total energy, the particle which fell into the black hole must have had a negative energy (with respect to an observer far away from the black hole). By this process the black hole loses mass, and to an outside observer it would appear that the black hole has just emitted a particle.

An important difference between the black hole radiation as computed by Hawking and a thermal radiation emitted from a black body is that the latter is statistical in nature, and only its average satisfies what is known as Planck's law of black body radiation, while the former satisfies this law exactly. Thus a thermal radiation contains information about the body that emitted it, while Hawking radiation seems to contain no such information, and depends only on the mass, angular momentum and charge of the black hole. This leads to the Black hole information paradox.

However, according to the conjectured gauge-gravity duality (also known as the AdS/CFT correspondence), black holes in certain cases (and perhaps in general) are equivalent to solutions of quantum field theory at a non-zero temperature. This means that no information loss is expected in black holes (since no such loss exists in the quantum field theory), and the radiation emitted by a black hole is probably a usual thermal radiation. If this is correct, then Hawking's original computation should be corrected, though it is not known how (see below).