If I understand correctly, some black holes “evaporate” over time by releasing Hawking radiation back to the universe.
Also if I understand correctly, the background radiation is the same everywhere in the universe since all the universe has the same age.
I am not sure if Hawking’s radiation counts as new space time. But if there was some way to measure the background radiation for the mass/energy created by the Hawking radiation, will it be the same as the universe’s background radiation ?
Stephen Hawking emits radiation?
I believe you are talking about two different effects.
Cosmic background radiation is universal, omnidirectional, and remarkably isotropic – pretty much the same in all directions. It is conventionally described as the “last echoes of the big bang.”
Hawking radiation happens across very high gravitational boundaries. Not only near black holes but it has also been observed near large atomic nuclei. (“The Breakdown of Empty Space” – article in Scientific American some years ago.) Essentially, a particle/anti-particle pair pops into existence, and then pops out again – this happens all the time, and is called “virtual particles.” The effect is not observable. But sometimes, one of the pair is pulled into a gravitational well – a black hole or a Uranium nucleus – so that the other particle doesn’t mutually annihilate with it, but wanders off, free, so that it appears to be “emitted” from the gravitational source.
I think these two different effects have nothing to do with each other.
Moderator Note
Please don’t give a joke answer in GQ until after some factual answers have been given.
Colibri
General Questions Moderator
Thank you for the reply Trinopus. My question is exactly on the universality of the cosmic radiation - is the cosmic background radiation present only in space-time created at the big-bang or is it also the same in new space -time created like Hawking radiation.
It’s still a confusing question.
Are you asking “Is there a mechanism, similar to Hawking radiation, where spacetime can be created and not automatically cancelled out by recombining with it’s anti-self?”
You see the problem with that statement? With virtual particles, you have pairs that when combined canceled out. Hawking radiation is simply what you get if one of the particles fails to recombined due to crossing an event horizon.
To extend that idea to spacetime, we would need a theory that allows for spacetime to exist in “pieces” and for these “pieces” to exist in 1 of 2 states and that on when recombined result in something, but nothing too strange. As far as I know we have no such theory and I while I’ve heard of theories where spacetime is granular the description was closer to tiles than particles.
Okay - I am not a physicist - so please bear with me. I will try to ask the question in a different way.
As I understand, the Big Bang is a singularity. It makes no sense to ask what the universe was like before the big bang. All of the universe (mass , space, time and all) have the timestamp of the start of the universe i.e. the background radiation.
As I also understand, a black hole is also a singularity. Although here it does makes sense (?) to ask what the black hole was before it became a black hole. So when the “matter” is recycled back from the black hole to the universe - does it retain the time stamp of the start of the universe (i.e. background radiation), or is the matter recycled back from the black hole have a time-stamp of its new creation date.
‘Radiation’ can mean different things. The Cosmic Background Radiation is basically (faint) microwave -length electromagnetic waves (like we’re in a giant, very low powered microwave); it’s just like light but a different wavelength.
Hawking radiation is not electromagnetic waves, but rather an irregular stream of particles flowing outward from the black hole.
So they’re really not the same kind of thing at all.
I think you’re confusing the cosmic background radiation with radiation dating techniques. Lets assume so and that way I can talk nonsense.
Current understanding is that the universe was incredibly energetic in its youth. As the universe expanded the energy density dropped and things started to happen. Fundamental forces differentiated, quarks and electrons start showing up and photons are bouncing around everywhere but are continually being re-absorbed so there’s no free path for them to race off without being destroyed.
Spacetime expands further and thing cool down a little more an you wind up with quarks grouping together into protons which suddenly capture electrons and we have hydrogen. We also suddenly have a free path for photons to go racing off. This all takes place roughly 300,000 years after the initial expansion. The free photons are energetic and are from every part of spacetime. fast forward billions of years and when we look out into space we see some of these photons but they’ve been red shifted (“cooled” I guess would work) to the temperature we see today ~2.7K.
Back to hawking radiation. As you move to smaller and smaller regions of spacetime there’s a seething bath of virtual particles. Since they immediately cancel out there’s no net average change in the local energy density. However if the pair appear at an event horizon, one particle may slip over before it can recombine. The radiation doesn’t originate from the black hole so it can’t really tell you anything about it. The event horizon is just a place where this splitting can take place.
You’re confused by the use of the word radiation in both contexts. It’s analogous to dark matter and dark energy. People see the word dark in both and think there must be a connection. There isn’t. Dark merely means unknown.
Hawking radiation is not at all like cosmic background radiation. For that matter, neither comes directly from a black hole. Hawing radiation is emitted at the event radius. The cosmic background radiation is the remnant of the entire universe at the time of inflation, which happened after the universe emerged from the singularity. And a singularity might not be a black hole. Singularity merely means not expressible in current physics.
As above - the word singularity doesn’t define any sort of physical thing. Rather it does the opposite. It says - “here be dragons” or “all our rules break down here, we have no clue”. The Big Bang started with a singularity - aka a point of “we have no clue”. There are other things for which we have no clue as well. The middle of a black hole being one. But you can’t really equate two different instances of “we have no clue”.
Grey - I think I know the difference between cosmic background radiation and radiation dating techniques.
I am using Hawking radiation as an example of the energy/matter recycled back from a singularity (black hole) to the universe. If it makes more sense to you - then consider matter recycled back from a black hole New study shows black holes recycle matter and energy back into space - Raw Story
So if one were to measure the back ground radiation around this matter - will it show the signature of the big bang or the signature of the black hole ?
[QUOTE=Francis Vaugha]
There are other things for which we have no clue as well. The middle of a black hole being one.
[/QUOTE]
We do have one BIG clue for the middle of the black hole - that the matter in it came from the Big Bang. The question is - when a black hole like this “evaporates” back into the universe, does the recycled matter appears as it was created at the big bang ? or does it have a different background signature ?
No, absolutely not.
Nor is the matter inside the black hole recycled and create a signature. Energy is subtracted from the black hole by the separation of pairs of identical virtual particles. This tells us nothing about what is inside the black hole. It is a different process leading to a different outcome. They have no similarity except that they happen to use the word radiation.
So if one were to measure the background radiation around this recycled matter - it wont be the same as the rest of the universe ? Am I understanding you correctly ?
The CMBR is the remnant of the Big Bang - it is a remnant because of the expansion of the universe. It will continue to become further red-shifted as the universe ages further. It is a black body radiation (indeed it is the most perfect black body we know of, fitting the theoretical spectrum to silly accuracy.)
An evaporating black-hole doesn’t have background radiation (other than the CMBR) but it does itself radiate. I have no idea if the spectra of Hawking radiation is a black body. I would guess it might be. But even if it is, the temperature it represents has no relationship to the CMBR. There is common physics, but that is all.
The question of recovering information out of an evaporating black hole about what went in, is one of the more interesting outstanding questions.
To add. Indeed Hawking radiation is exactly black body. Not surprised.
So, the difference is that the CMBR is the remnant of the early hot universe at the point it had cooled to become transparent. It isn’t a remnant of the Big Bang directly, it is quite a bit later. The universe expands and this all pervading radiation gets stretched out so much that it is red-shifted right down to microwaves, and the equivalent black body is seriously cold. That is all it is. It isn’t in any way a special signature of the Big Bang.
Hawking radiation has a spectrum that is related directly to the mass of the black hole.
They are both black bodies. End of story.
There does remain the question of conservation of information. Quantum theory doesn’t like information to be destroyed. But an evaporating black hole doesn’t transmit information from within itself, even as it becomes diminished to nothingness. This is a source of problems. There are some suggestions, but I’m not sure anyone is satisfied with the current state of understanding.
There is no background radiation. There is no recycled matter. Your understanding of Hawking radiation is completely wrong. You have a garbled mental picture of what is happening. Please read what the physicists here are trying to explain to you.
The cosmic microwave background is not an inherent feature of the fabric of space, or anything like that. If you build a sealed box surrounded by wire mesh with a spacing of less than a millimeter or so, then that box will contain no CMB radiation. If you open it up and expose it to the sky, then microwaves will enter it. Any given microwave photon will only be in the box for a very short time before hitting the back wall, but as long as the box remains open and exposed, it’ll be replaced by other photons coming in. Close the box, and new photons stop coming in, and the photons that were in the box at the time all hit the back of the box.
Honestly, you don’t seem to.
You misunderstand the linked story. The article is pointing out that galactic black holes are engines for moving matter about galaxies. They rip apart material in their accretion disks which then get caught up in their intense tangle of fields which throws some of those materials out of the galactic core.
It says nothing about materials which pass the event horizon being recycled.
Look, Hawking radiation, at the event horizon effectively has a particle escaping into space and the other passing into the blackhole. That’s it. The particles do not come from the black hole.
If I understand him correctly, Susskind had a long-running disagreement with Hawking about black holes and entropy. I am poorly equipped to discuss this, so please take this with a grain of salt.
Hawking felt that stuff fell into a black hole and was essentially lost forever. While a black hole could evaporate, the Hawking Radiation had no strict relation to that which had fallen in.
Susskind felt that this created information loss unacceptable to quantum theory.
This debate was ultimately resolved in Susskind’s favor, and Hawking published a paper proving Susskind correct.
I think that somehow the information of stuff that fell in is encoded in the Hawking radiation. I don’t much understand it. Hopefully someone will explain this shortly.
I don’t know that it would be possible, even for Brainiac, to decipher Hawking radiation to learn anything meaningful about stuff that fell in. Even if you could do that, except for the possible but unconfirmed existence of quantum black holes created in the Big Bang, black holes are born of dying stars and arrived on the scene long after the Big Bang.