Jul 16, 2024 03:58 PM
https://www.sciencefocus.com/space/whats...black-hole
EXCERPTS: Perhaps the most surprising scientific discovery of the last decade is that the Universe is teeming with black holes...
[...] Arguably the most detailed and developed theory of quantum spacetime is loop quantum gravity, or LQG – a tentative quantum gravity theory that has been steadily developing since the late 1980s.
Thanks to this theory, an interesting answer to these questions [about black holes] has emerged. That answer is given by the following scenario. The interior of a black hole evolves until it reaches a phase where quantum effects begin to dominate.
This creates a powerful repulsive force that reverses the dynamics of the interior of the collapsing black hole, making it ‘bounce back’. After this quantum phase, described by LQG, the spacetime inside the hole is once again governed by Einstein’s theory, except that now the black hole is expanding rather than contracting.
The possibility of an expanding hole is indeed predicted by Einstein’s theory, in the same manner in which black holes were predicted. It’s a possibility that has been known about for decades; so long, in fact, that this corresponding spacetime region even has a name: it’s called a ‘white hole’.
[...] This scenario answers both questions posed earlier. What happens at the end of the evaporation is that a black hole quantum leaps into a long-living tiny white hole. And the matter that falls into a black hole can later exit from this white hole.
[...] Most of the energy of the matter will have already been radiated away by Hawking radiation – low-energy radiation emitted by the black hole due to quantum effects that cause it to evaporate. What exits the white hole isn’t the energy of the matter that fell in it, but residual low-energy radiation, which nevertheless carries all the residual information about the matter that fell in.
An intriguing possibility opened by this scenario is that the mysterious dark matter that astronomers see the effects of in the sky could actually be formed, entirely or in part, by tiny white holes generated by ancient evaporated black holes. These could have been produced in early phases of the Universe, possibly in the pre-Big Bang phase that appears to be also predicted by LQG.
This is an attractive possible solution to the mystery of the nature of dark matter, because it provides an understanding of dark matter that relies solely on General Relativity and quantum mechanics, both well-established aspects of nature. It also doesn’t add ad hoc particles of fields, or new dynamical equations, as most of the alternative tentative hypotheses about dark matter do.
[...] So, can we detect white holes? Direct detection of a white hole would be difficult because these tiny objects interact with the space and matter around them almost uniquely through gravity, which is very weak. It’s not easy to detect a hair using only its gravitational attraction. But perhaps it won’t remain impossible as technology advances. Ideas on how to do so using detectors based on quantum technology have already been proposed... (MORE - missing details)
EXCERPTS: Perhaps the most surprising scientific discovery of the last decade is that the Universe is teeming with black holes...
[...] Arguably the most detailed and developed theory of quantum spacetime is loop quantum gravity, or LQG – a tentative quantum gravity theory that has been steadily developing since the late 1980s.
Thanks to this theory, an interesting answer to these questions [about black holes] has emerged. That answer is given by the following scenario. The interior of a black hole evolves until it reaches a phase where quantum effects begin to dominate.
This creates a powerful repulsive force that reverses the dynamics of the interior of the collapsing black hole, making it ‘bounce back’. After this quantum phase, described by LQG, the spacetime inside the hole is once again governed by Einstein’s theory, except that now the black hole is expanding rather than contracting.
The possibility of an expanding hole is indeed predicted by Einstein’s theory, in the same manner in which black holes were predicted. It’s a possibility that has been known about for decades; so long, in fact, that this corresponding spacetime region even has a name: it’s called a ‘white hole’.
[...] This scenario answers both questions posed earlier. What happens at the end of the evaporation is that a black hole quantum leaps into a long-living tiny white hole. And the matter that falls into a black hole can later exit from this white hole.
[...] Most of the energy of the matter will have already been radiated away by Hawking radiation – low-energy radiation emitted by the black hole due to quantum effects that cause it to evaporate. What exits the white hole isn’t the energy of the matter that fell in it, but residual low-energy radiation, which nevertheless carries all the residual information about the matter that fell in.
An intriguing possibility opened by this scenario is that the mysterious dark matter that astronomers see the effects of in the sky could actually be formed, entirely or in part, by tiny white holes generated by ancient evaporated black holes. These could have been produced in early phases of the Universe, possibly in the pre-Big Bang phase that appears to be also predicted by LQG.
This is an attractive possible solution to the mystery of the nature of dark matter, because it provides an understanding of dark matter that relies solely on General Relativity and quantum mechanics, both well-established aspects of nature. It also doesn’t add ad hoc particles of fields, or new dynamical equations, as most of the alternative tentative hypotheses about dark matter do.
[...] So, can we detect white holes? Direct detection of a white hole would be difficult because these tiny objects interact with the space and matter around them almost uniquely through gravity, which is very weak. It’s not easy to detect a hair using only its gravitational attraction. But perhaps it won’t remain impossible as technology advances. Ideas on how to do so using detectors based on quantum technology have already been proposed... (MORE - missing details)