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bassplayer142
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I've heard that black holes disappear when they are done. Doesn't it make sense to say it would end in a form like a neutron star?
Forever is a bit tricky - it depends on your end of universe model - but basically yes, there is no obvious way to get rid of a large black hole.bassplayer142 said:So it is accepted now that large black holes will last forever?
bassplayer142 said:So it is accepted now that large black holes will last forever?
Heneni said:What do you mean when you say the black hole 'evaporates'.
George Jones said:Through a quantum process, black holes radiate particles (and anti-particles), and thus lose mass. As they lose mass, that rate at which they radiate increases.
Much slower, the rate of mass loss depends on the mass. Larger holes lose at a slower rate.Heneni said:If the black hole looses mass by radiation, it must loose its mass at a slower rate than it is gaining mass right? At least in order for the black hole to grow.
Anything that goes past event horizon would contribute to the mass, while the radiation takes some of the mass away. Correct?
What kind of factors would determine whether the rate of evaporation is higher than the rate of mass growth?
I don't know what energy they would have, or even if they have a particular energy.And would the evaporation be what they call high energy cosmic rays? The kind that does not come from the sun of course.
The particles don't come out of the black hole. They are created from the energy near the event horizon. One of the pair goes into the black hole - one escapes. The escaping one effectively removes some energy.If matter goes into the hole and radiation comes out in the form of particles, then do those particles have a speed higher than that of light? I figured such a thing can't be found.
Heneni said:What kind of factors would determine whether the rate of evaporation is higher than the rate of mass growth?
But what about the black holes?
Well, they probably evaporate due to Hawking radiation: a solar-mass black hole should do so in 1066 years, and a really big one, comparable to the mass of a galaxy, should take about 1099 years.
Actually, a black hole only shrinks by evaporation when it's in an environment cooler than the temperature of its Hawking radiation - otherwise, it grows by swallowing thermal radiation. The Hawking temperature of a solar-mass black hole is about 6 x 10-8 Kelvin, and in general, it's inversely proportional to the black hole's mass. The universe should cool down below 10-8 Kelvin very soon compared to the 1066 years it takes for a solar-mass black holes to evaporate. However, before that time, such a black hole would grow by absorbing background radiation - which makes its temperature decrease and help it grow more!
If a black hole ever grew to about 1022 solar masses, its Hawking temperature would go below 10-30 Kelvin, which would allow it to keep growing even when the universe has cooled to its minimum temperature. Of course, 1022 solar masses is huge - about the mass of the currently observable universe! But it would take a nontrivial calculation to show that reasonable-sized black holes have no chance of getting this big. I think it's true, but I haven't done the calculation.
For now, let's assume it's true: all black holes will eventually shrink away and disappear - none of them grow big enough to stick around when it gets really cold.
Heneni said:Thank you!
If the black hole looses mass by radiation, it must loose its mass at a slower rate than it is gaining mass right? At least in order for the black hole to grow.
Anything that goes past event horizon would contribute to the mass, while the radiation takes some of the mass away. Correct?
What kind of factors would determine whether the rate of evaporation is higher than the rate of mass growth?
Heneni
mgb_phys said:The particles don't come out of the black hole. They are created from the energy near the event horizon. One of the pair goes into the black hole - one escapes. The escaping one effectively removes some energy.
Pretty much yes.Heneni said:So energy at the (edge of the?) horison creates this pair of particles, some of the energy is lost as one pair of the particles moves away from the horizon. Ok...so according to E = mc2 if the black hole looses energy by the escaping particle then it will loose mass.
The event horizon is the distance from a black hole where you cannot escape if you get closer than this. In classical terms it's the distance at which the escape velocity is > the speed of light.Its just...im trying to wrap my head around a particle that is created from the energy of the black hole horizon, yet being able to escape it, carrying with it some energy, and therefore some mass.
George Jones said:Forever is a long time. Current observation and theoretical evidence indicate that the universe will expand forever.
Dmitry67 said:Not exactly, I believe that the 'Big Rip' scenario is the most realistic one.
A black hole is a region in space where the gravitational pull is so strong that nothing, including light, can escape from it. This happens when a massive star collapses in on itself, creating a singularity.
A black hole can "die" through a process called Hawking radiation, where it slowly loses mass over time and eventually disappears. However, this process takes an extremely long time, on the order of trillions of years.
No, a black hole cannot turn into a neutron star. A neutron star is formed when a massive star undergoes a supernova explosion, while a black hole is formed from a collapsed star. These are two different processes that cannot be reversed.
The matter inside a black hole is crushed into an extremely dense singularity, where the laws of physics as we know them break down. It is impossible for us to know what happens inside a black hole, as no information can escape from it.
According to current theories, a black hole can eventually disappear through Hawking radiation. However, this process takes an extremely long time and no black hole has been observed to completely disappear yet. It is also possible that black holes may merge with each other, but this would result in a larger black hole rather than its disappearance.