Colby College Astronomy Blog

Hawking Radiation and evaporation of black holes

                Many theorize that there is nothing within a Black Hole, or more clearly no temperature or light. Within the Event Horizon, the point within a black hole where not even light can escape; the gravitational forces are so strong that anything passing the Event Horizon, including light, will never be able to escape. This theory that nothing can escape a black hole is theoretically sound because there is nothing faster than the speed of light. The only way matter could escape the gravitational pull beyond the event horizon would be if it were faster than the speed of light. While scientist have not been able to see a Black Hole close enough to determine whether or not it gives off blackbody radiation, Stephen  Hawking believes that a Black Hole can give off radiation and energy. This theory is known as Hawking Radiation. Hawking Radiation as well helps with the theory that Black Holes can evaporate by giving off energy.

Image credit: https://qph.ec.quoracdn.net/main-qimg-527e8a63b6a99759434c841f1f8bf28b-c?convert_to_webp=true

What is Hawking Radiation?

                 Due to the principles of Quantum Mechanics allows some form of energy to escape the event horizon and the black hole[1]. While classical mechanics does not allow this idea of energy escape.  If a black hole gives off a blackbody radiation what is creating this energy when everything that a black hole absorbs cannot escape? The energy that the black hole is giving off is radiating right before the event horizon. This energy is in the form of particles and antiparticle know as Virtual Particles. Their interaction with each other create this energy. 

Image credit: http://casa.colorado.edu/~ajsh/hawk.html

What do the Virtual Particles do and how they relate to Hawking radiation and energy?

                While Hawking Radiation is not proved to be correct, Stephen Hawking theorized that this energy escapes the Event Horizon as Virtual Particles. Virtual Particles are these theoretical particles move at such a fast speed that they cannot be seen, or virtually nonexistent. A virtual particle is composed of both a particle and an antiparticle the two separate, but then are attracted to each other and collide annihilating both. Virtual Particles in every section of space, only existing and annihilating at such a speed they cannot be seen.  This phenomenon occurs at such a fast rate that they cannot be seen, everywhere except on the event horizon of a black hole. On the Event Horizon, this separation can be seen because of the gravitational pull of the event horizon. While one particle is pulled within the black hole and disappears, the other is shot out of the event horizon.

Image credit: http://ircamera.as.arizona.edu/Astr2016/text/extplaydice.htm

 Evaporation of a black hole

              Only occurring after all matter surrounding the black hole has been absorbed. Virtual particles directly cause black holes to lose mass. This separation of Virtual particles causes a loss of a minutely small amount of energy due to the kinetic energy used when the particles separate. This loss of kinetic energy is because the particle and antiparticle are attracted to each other, for them to separate the black hole must use energy to separate them and thus lose mass. The idea of particles tunneling can also describe the loss of energy in a black hole. The Heisenberg uncertainty principle determines that the wavelength of a particle is an uncertainty. Because momentum and position cannot be precise for a particle, this uncertainty allows particles to exist inside or near the event horizon. The particle can then tunnel out of the black hole and cause it to lose a minute amount of mass.  While the energy loss is not even significant, over a long period this loss of energy will become significant, and the black hole would shrink and evaporate. This shrinking and evaporation of the Black hole cause it to become hotter as mass is inversely proportional to mass in a black hole as well decreases entropy.  This process would take over the life of the universe to take place, but it would evaporate.

 Conclusion

 For us to prove or disprove the idea of Hawking radiation and evaporation of black holes in nature rather than just in a laboratory could only be possible with the existence of micro black holes. The reason why they could be observed and help prove this theory is because they are so small that they could potentially evaporate right now.

In case you want to hear the same relative idea but through the voice of Morgan Freeman, click on this video below.

https://www.youtube.com/watch?v=1wHdtP0U6JA

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[1].Hamilton, Andrew. "Hawking Radiation." casa.colorado.edu. Last modified April 19, 1998. Accessed November 8, 2016. http://casa.colorado.edu/~ajsh/hawk.html.

Sources used:

Hamilton, Andrew. "Hawking Radiation." casa.colorado.edu. Last modified April 19, 1998. Accessed November 8, 2016. http://casa.colorado.edu/~ajsh/hawk.html.

Baez, John. "Hawking Radiation." math.ucr, University of California Riverside, 1994, math.ucr.edu/ 

     home/baez/physics/Relativity/BlackHoles/hawking.html. Accessed 1997.