Jul 9, 2020 06:52 PM
(This post was last modified: Jul 9, 2020 06:55 PM by C C.)
https://www.forbes.com/sites/startswitha...les-decay/
EXCERPT (Ethan Siegel): . . . What Hawking would have had us imagine is a relatively simple picture. Start with a black hole: a region of space where so much mass has been concentrated into such a small volume that, within it, not even light can escape. Everything that ventures too close to it will inevitably be drawn into the central singularity, with the border between the escapable and inescapable regions known as the event horizon.
Now, let's add in quantum physics. Space, at a fundamental level, can never be completely empty. Instead, there are entities inherent to the fabric of the Universe itself — quantum fields — that are always omnipresent. And, just like all quantum entities, there are uncertainties inherent to them: the energy of each field at any location will fluctuate with time. These field fluctuations are very real, and occur even in the absence of any particles.
In the context of quantum field theory, the lowest-energy state of a quantum field corresponds to no particles existing. But excited states, or states that correspond to higher-energies, correspond to either particles or antiparticles. One visualization that's commonly used is to think about empty space as being truly empty, but populated by particle-antiparticle pairs (because of conservation laws) that briefly pop into existence, only to annihilate away back into the vacuum of nothingness after a short while.
It's here that Hawking's famous picture — his grossly incorrect picture — comes into play. All throughout space, he asserts, these particle-antiparticle pairs are popping in and out of existence. Inside the black hole, both members stay there, annihilate, and nothing happens. Far outside of the black hole, it's the same deal. But right near the event horizon, one member can fall in while the other escapes, carrying real energy away. And that, he proclaims, is why black holes lose mass, decay, and where Hawking radiation comes from.
That was the first explanation that I, myself a theoretical astrophysicist, ever heard for how black holes decay. If that explanation were true, then that would mean:
What's odd about this explanation is that it's not the one he used in the scientific papers he wrote concerning this topic. He knew that this analogy was flawed and would lead to physicists thinking incorrectly about it, but he chose to present it to the general public as though people weren't capable of understanding the real mechanism actually at play. And that's too bad, because the actual scientific story is no more complex, but far more illuminating... (MORE - details)
EXCERPT (Ethan Siegel): . . . What Hawking would have had us imagine is a relatively simple picture. Start with a black hole: a region of space where so much mass has been concentrated into such a small volume that, within it, not even light can escape. Everything that ventures too close to it will inevitably be drawn into the central singularity, with the border between the escapable and inescapable regions known as the event horizon.
Now, let's add in quantum physics. Space, at a fundamental level, can never be completely empty. Instead, there are entities inherent to the fabric of the Universe itself — quantum fields — that are always omnipresent. And, just like all quantum entities, there are uncertainties inherent to them: the energy of each field at any location will fluctuate with time. These field fluctuations are very real, and occur even in the absence of any particles.
In the context of quantum field theory, the lowest-energy state of a quantum field corresponds to no particles existing. But excited states, or states that correspond to higher-energies, correspond to either particles or antiparticles. One visualization that's commonly used is to think about empty space as being truly empty, but populated by particle-antiparticle pairs (because of conservation laws) that briefly pop into existence, only to annihilate away back into the vacuum of nothingness after a short while.
It's here that Hawking's famous picture — his grossly incorrect picture — comes into play. All throughout space, he asserts, these particle-antiparticle pairs are popping in and out of existence. Inside the black hole, both members stay there, annihilate, and nothing happens. Far outside of the black hole, it's the same deal. But right near the event horizon, one member can fall in while the other escapes, carrying real energy away. And that, he proclaims, is why black holes lose mass, decay, and where Hawking radiation comes from.
That was the first explanation that I, myself a theoretical astrophysicist, ever heard for how black holes decay. If that explanation were true, then that would mean:
- Hawking radiation was composed of a 50/50 mix of particles and antiparticles, since which member falls and which one escapes will be random,
- that all of the Hawking radiation, which causes black holes to decay, will be emitted from the event horizon itself, and
- that every quantum of emitted radiation must have a tremendous amount of energy: enough to escape from almost, but not quite, being swallowed by the black hole.
What's odd about this explanation is that it's not the one he used in the scientific papers he wrote concerning this topic. He knew that this analogy was flawed and would lead to physicists thinking incorrectly about it, but he chose to present it to the general public as though people weren't capable of understanding the real mechanism actually at play. And that's too bad, because the actual scientific story is no more complex, but far more illuminating... (MORE - details)