We do not live in the first universe. A group of physicists said that there were other universes, in other eons, before ours. Like ours, these universes were full of black holes. And we can detect traces of these long-dead black holes in the cosmic microwave background (CMB), the radioactive remnant of our universe’s violent birth.
At least, this is the somewhat eccentric view of a group of theorists, including the eminent mathematical physicist at the University of Oxford, Roger Penrose (also an important collaborator of Stephen Hawking). Penrose and his assistants claim that this is a modified version of the Big Bang.
In Penrose’s history of space and time (what physicists call conformal cyclic cosmology, or CCC), universes successively bubble, expand, and die, with black holes from each leaving traces in the universes.
A new paper published Aug. 6 in the preprint journal arXiv presents clear evidence for Hawking points in the CMB sky. Penrose, along with SUNY mathematician Daniel Ahn and Warsaw University theoretical physicist Krzysztof Meissner, argue that these traces are visible in existing CMB data.
Daniel Ahn explained how these footprints form and survive from one aeon to the next.
“If the universe goes on and on and black holes gobble up everything, at some point we will only have black holes,” he told Live Science. According to Hawking’s most famous theory, black holes slowly lose some of their mass and energy over time due to the emission of massless particles called gravitons and photons. If this Hawking radiation exists, “then what will happen is that these black holes will gradually, gradually shrink.”
At some point, these black holes will completely disintegrate, Ahn said, leaving the universe a massless soup of photons and gravitons.
“The point is that massless gravitons and photons don’t really experience time or space,” he said.
Gravitons and photons, massless travelers at the speed of light, do not experience time and space in the same way that we do – and all other massive, slower moving objects in the universe. Einstein’s theory of relativity dictates that objects with mass are likely to move slower in time as they approach the speed of light, and distances become distorted from their point of view. Massless objects like photons and gravitons move at the speed of light, so they don’t experience time or distance at all.
“So a universe filled with only gravitons or photons would have no idea what time or space is,” Ahn said.
At this point, say some physicists (including Penrose), the vast, empty universe after the black hole is beginning to resemble the super-compressed universe at the moment of the Big Bang, where there is no time or distance between anything.
“And then it starts all over again,” Ahn said.
So, if the new universe does not contain any black holes from the previous universe, how can these black holes leave traces in the CMB?
Penrose said the traces are not from the black holes themselves, but rather from the billions of years it took these objects to release energy into their own universe via Hawking radiation.
“It’s not a black hole singularity,” he told Live Science, “or it’s a real physical body,” but… all of the hole’s Hawking radiation throughout its history.
Here’s what that means: every time a black hole dissolves with Hawking radiation, it leaves a trail. And this label, made at the frequencies of the background radiation of space, can survive the death of the universe. If researchers could detect this mark, then scientists would have reason to believe that the CCC’s vision of the universe is correct, or at least not necessarily wrong.
To detect this faint mark against the already faint, entangled CMB radiation, Ahn said he ran a sort of statistical tournament among the patches of the sky.
Ahn took round regions in the third part of the sky where galaxies and starlight do not overwhelm the CMB. He then identified regions where the microwave frequency distribution matches what would be expected if Hawking points existed. These circles “competed” with each other to determine which area best matched the expected spectra of Hawking’s dots, he said.
He then compared this data with fake CMB data that he randomly generated. This trick was to eliminate the possibility that these preliminary “Hawking points” could form if the CMB were completely random. If the randomly generated CMB data could not mimic these Hawking points, this strongly suggests that the newly identified Hawking points were indeed from black holes of past eras.
When asked if black holes from our universe could ever leave traces in the universe of the next eon, Penrose replied: “Yes, indeed!”