What are Hawking Emissions?

Question

What are Hawking Emissions?

Answer 1

Hawking emissions i am pretty sure are neutrino energy released from black holes, the only energy actually able to escape the event horizon and also the only reason they are detectable.

Maybe not neutrino energy but it is energy able to escape the event horixon making black holes detectable...

Answer 2

It is not necessarly nutrino

They are radiations emmitted by a BlackHole.
Actually it is emmitted by the surroundins of the black hole the process is well explained in Hawkins book Breif History of Time.
If you know anhelliation you can think of its reverse process. Energy giving a particle and antiparticle.
Similarly the free space can produce energy,negetive energy pairs.




How is it possible that a black hole appears to emit particles when we know that nothing can escape from within its
event horizon? The answer, quantum theory tells us, is that the particles do not come from within the black hole, but
from the “empty” space just outside the black hole’s event horizon! We can understand this in the following way: what
we think of as “empty” space cannot be completely empty because that would mean that all the fields, such as the
gravitational and electromagnetic fields, would have to be exactly zero. However, the value of a field and its rate of
change with time are like the position and velocity of a particle: the uncertainty principle implies that the more
accurately one knows one of these quantities, the less accurately one can know the other. So in empty space the field
cannot be fixed at exactly zero, because then it would have both a precise value (zero) and a precise rate of change
(also zero). There must be a certain minimum amount of uncertainty, or quantum fluctuations, in the value of the field.
One can think of these fluctuations as pairs of particles of light or gravity that appear together at some time, move
apart, and then come together again and annihilate each other. These particles are virtual particles like the particles
that carry the gravitational force of the sun: unlike real particles, they cannot be observed directly with a particle
detector. However, their indirect effects, such as small changes in the energy of electron orbits in atoms, can be
measured and agree with the theoretical predictions to a remarkable degree of accuracy. The uncertainty principle also
predicts that there will be similar virtual pairs of matter particles, such as electrons or quarks. In this case, however,
one member of the pair will be a particle and the other an antiparticle (the antiparticles of light and gravity are the same
as the particles).
Because energy cannot be created out of nothing, one of the partners in a particle/antiparticle pair will have positive
energy, and the other partner negative energy. The one with negative energy is condemned to be a short-lived virtual
particle because real particles always have positive energy in normal situations. It must therefore seek out its partner
and annihilate with it. However, a real particle close to a massive body has less energy than if it were far away,
because it would take energy to lift it far away against the gravitational attraction of the body. Normally, the energy of
the particle is still positive, but the gravitational field inside a black hole is so strong that even a real particle can have
negative energy there. It is therefore possible, if a black hole is present, for the virtual particle with negative energy to
fall into the black hole and become a real particle or antiparticle. In this case it no longer has to annihilate with its
partner. Its forsaken partner may fall into the black hole as well. Or, having positive energy, it might also escape from
the vicinity of the black hole as a real particle or antiparticle Figure 7:4.
file:///C|/WINDOWS/Desktop/bla... Hawking - A brief history of time/f.html (4 of 8) [2/20/2001 3:15:18 AM]
Figure 7:4
To an observer at a distance, it will appear to have been emitted from the black hole. The smaller the black hole, the
shorter the distance the particle with negative energy will have to go before it becomes a real particle, and thus the
greater the rate of emission, and the apparent temperature, of the black hole.
The positive energy of the outgoing radiation would be balanced by a flow of negative energy particles into the black
hole. By Einstein’s equation E = mc2 (where E is energy, m is mass, and c is the speed of light), energy is proportional
to mass. A flow of negative energy into the black hole therefore reduces its mass. As the black hole loses mass, the
area of its event horizon gets smaller, but this decrease in the entropy of the black hole is more than compensated for
by the entropy of the emitted radiation, so the second law is never violated.
A Brief History of Time - Stephen Hawking... Chapter 7

Answer 3

If time speeds up, relatively, in a deep gravity well, to what extent must it be affected by a black hole?

Hawking Emissions represent a departure from the notion that the speed of light is a terminal velocity in our space/time neighbourhood.

Therefore, "Why" is a better question than "What" regarding Hawking Emissions..

Answer 4

Hawking emissions (...or Hawking radiation) is the name given to the theoretical process by which black holes seem to radiate energy. Quantum physics has shown that at size scales smaller than 1.6^ minus 35 meters (...about 10^ minus 20 times smaller than a proton) subatomic particles are created out of the vacuum. Each creation event makes one particle and its anti-particle twin. The pair almost immediately self-annihilate each other. However, in the intense gravitational field of a black hole it's possible for one particle of the pair to be sucked into the black hole before the they destroy each other. This leaves one particle behind, thus giving the appearance of having been emitted from the black hole.

Answer 5

The Hawking Radiation theory states that virtual particle/anti-particle are sometimes created outside the event horizon of black holes and three things can happen.
1. Both particles are pulled into the black hole
2. Both particles escape from the balck hole
3. One particular is sucked in and the other escapes.
For the third possibility, the particle that escapes is the real and can be observed from the earth. The particle gets sucked in remains virtual and must restore its conservation of energy by giving itself a negative mass-energy.
The blackhole absorbes this negative mass-energy and looses mass and thus appears to shrink. The rate of power emiision is proportional to the inverse square of the blackhole's mass. (Ref: High energy Astrophysics Learning Centre.)
Ramachandran V.