The Life and Death of Blackholes

[psycho_childe]

I am an australian high school student and was watching a program on tv explaining one of Steven Hawkings theroes about negative-positive particle cancelation and blackholes, and the came up with 2 questions:

 

1) If a blackhole is absorbing energy from light and chemicular reactions of normal particles, while also absorbing anti-matter particles (created in close proximity to the blackhole) that can decrease the said blackholes mass, does the energy increase the number of anti-matter particles created close to the blackhole that are then absorbed by it?

2) If so then is there a possibility that an equilibrium state can be made where the current mass of the blackhole equals the mass of simultaniusly absorbed anti-matter particles resulting in the sudden ceasation of the blackholes existance?

 

I've asked all of my science teachers but they just look at me in a fuuny way or walk away without comment.

[Mr Skeptic]

The thing about Hawking radiation is that it allows black holes to absorb one of a virtual particle/anti-particle pair. These pop into and out of existence in a vacuum due to quantum mechanics. In sucking in one of the pair, the black hole makes the other one a real particle, and the energy for this comes from the black hole. Therefore, the black hole loses mass-energy.

 

A black hole is so called because nothing, not even light, can escape from a black hole. If you take a black hole made of matter and one made of antimatter and collide them, they will make a bigger black hole. The matter and antimatter, if they still exist in said form (since you won't be able to tell the difference), could annihilate, but what would result? Light, which is still trapped in the black hole and has just as much mass-energy as the particles that annihilated to create it.

[psycho_childe]

I get that, but the original theory states that this virtual positive/negative is happening every where and when, and the blackhole is absorbing the negative. But the actual reaction is happening from a build up in energy that needs to disipate. Hence the positive/negative reaction. My question is asking that just by passing through a patch of space does light increase the number of times the negative/positive reaction happens.

[Spyman]

The strong gravity field from the Black Hole is whats causing the particle pair and it doesn't matter if it's a anti or normal particle thats fall back, it's the one who manages to escape that is the counted loss for the mass of the Black Hole. A Black Hole doesn't care whether the things it swallows is anti or normal matter, even energy like photons will contribute to the mass.

(One can view it like that instead it's the particle who falls back that has negative energy and the one that escapes has positive, but that is not the same as anti or normal matter which both has positive energy.)

 

The normal though would be that a bigger Black Hole would produce more particle pairs and thus loose more energy from Hawking radiation but it's the other way around. The "tension" in the metric of spacetime actually gets weaker at the Event Horizon for bigger Black Holes and therefor a Black Hole will radiate very little and slow at first and then more and more as it shrinks until it explodes in a final flash of radiation.

(Normal sized Black Holes is growing on the tiny diet of cosmic microwave background radiation alone, since they swallow more photons than they radiate due to their size.)

 

"Hawking radiation

Hawking radiation (also known as Bekenstein-Hawking radiation) is a thermal radiation with a black body spectrum predicted to be emitted by black holes due to quantum effects. It is named after the physicist Stephen Hawking who provided the theoretical argument for its existence in 1974, and sometimes also after the physicist Jacob Bekenstein who predicted that black holes should have a finite, non-zero temperature and entropy. Hawking's work followed his visit to Moscow in 1973 where Soviet scientists Yakov Zeldovich and Alexander Starobinsky showed him that according to the quantum mechanical uncertainty principle, rotating black holes should create and emit particles. The Hawking radiation process reduces the mass of the black hole and is therefore also known as black hole evaporation.

 

Because Hawking radiation allows black holes to lose mass, black holes that lose more matter than they gain through other means are expected to dissipate, shrink, and ultimately vanish. Smaller micro black holes (MBHs) are predicted to be larger net emitters of radiation than larger black holes, and to shrink and dissipate faster."

http://en.wikipedia.org/wiki/Hawking_radiation

 

 

I would think that a stream of photons passing through a patch of space, does affect the fabric of spacetime and thus slightly increase the creation/annihilations of particle pairs.

 

"Virtual particle

In physics, a virtual particle is a particle that exists for a limited time and space, introducing uncertainty in their energy and momentum due to the Heisenberg Uncertainty Principle. (Indeed, because energy and momentum in quantum mechanics are time and space derivative operators, then due to Fourier transforms their spans are inversely proportional to time duration and position spans, respectively).

 

Virtual particles exhibit some of the phenomena that real particles do, such as obedience to the conservation laws. If a single particle is detected, then the consequences of its existence are prolonged to such a degree that it cannot be virtual. Virtual particles are viewed as the quanta that describe fields of the basic force interactions, which cannot be described in terms of real particles. Examples of these are static force fields, such as a simple electric or magnetic field, or any field that exists without excitations that result in its carrying information from place to place.

 

Virtual particles should not be confused with antiparticles or virtual antiparticles."

http://en.wikipedia.org/wiki/Virtual_particle

[psycho_childe]

Ok, but if light is increasing the number of virtual particle collisions and the blackhole is pulling one of them into reality and absorbing the other does the number pulled into rerality have the capabilities of removing the black hole without violence, and what happens to the matter that is now caught in a non-existant gravity well?

Edited November 13, 2009 by psycho_childe
typos

[Spyman]

First off, light may increase the number of virtual particles, but in comparison to the strong gravity field of a Black Hole, I think it's best to neglect the miniscule effect, at least in this discussion. Also if the light gets caught by the BH it will contribute to it so that it grows instead of shrinks.

(Unless you have some hidden agenda I can't yet interpret.)

 

When the virtual particles escapes the BH and becomes real particles, the BH looses the same amount of matter/energy as the particles are worth. The BH radiates away it's own matter, so when it don't have any more matter to radiate away it will no longer excist and the matter that once was caught will now be transfered to energy and long gone as radiated heat.

 

Very small BHs will radiate away very fast and the only way stop that is to feed them so they grow instead, but that is also very messy and "violent".

 

One of the strongest and most fundamental laws of nature is that energy or matter can never be destroyed or created, but transformed into each other.

 

"Conservation of energy

The law of conservation of energy is an empirical law of physics. It states that the total amount of energy in a closed system remains constant over time (are said to be conserved over time). A consequence of this law is that energy cannot be created nor destroyed. The only thing that can happen to energy in a closed system is that it can change form, for instance chemical energy can become thermal energy.

 

Albert Einstein's theory of relativity shows that energy and mass are the same thing, and that neither one appears without the other. Thus in closed systems, both mass and energy are conserved separately, just as was understood in pre-relativistic physics. The new feature of relativistic physics is that "matter" particles (such as those constituting atoms) could be converted to non-matter forms of energy, such as light; or kinetic and potential energy (example: heat). However, this conversion does not affect the total mass of systems, since the latter forms of non-matter energy still retain their mass through any such conversion."

http://en.wikipedia.org/wiki/Conservation_of_energy