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Top Comments: Of Energetic Neutrinos and Primordial Black Holes [1]
['This Content Is Not Subject To Review Daily Kos Staff Prior To Publication.']
Date: 2025-09-18
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On February 23, 2023, physicists monitoring a light detector array in the Mediterranean Sea observed the most energetic neutrino ever observed. It was 30 times more energetic than its closest competitor. The energy of this neutrino is estimated to be about 220 PeV (or 220 million billion electron volts), which is thousands of times the energy of any particle collision at the Large Hadron Collider, the largest particle collider in the world. It was possible to correlate previously observed high-energy neutrinos with a source, which were usually the centers of distant galaxies with active black holes at their centers. However, partly because the detector in the Mediterranean Sea is still under construction, it was not possible to determine the source of this most energetic neutrino. Because this neutrino was so much more energetic that any previously detected ones, some physicists are considering other possible sources for this energy.
As such, physicists from MIT have come up with a new possible source: the death throes of primordial black holes. The black holes that most people pay attention to are the humongous ones at the centers of galaxies that have masses equivalent to billions of Suns and spew out streams of energetic particles, but primordial black holes are different. They are black holes that appeared very early in the history of the universe, according to simulations of that period, and they are much smaller than the more familiar galactic black holes. The masses of primordial black holes can range from the upper limit of a few hundred Sum masses down to the mass of an elementary particle.
The thing about primordial black holes (PBHs) is that they are unstable due to Hawking radiation. The late physicist Stephen Hawking postulated that black holes do emit radiation (his famous quote not eh subject being “Black holes ain’t so black.”) If, through the uncertainty principle, the creation of a particle-antiparticle pair happens just at the event horizon of a black hole, and one of these particles is inside the event horizon while the other is outside, the one outside has a chance to escape. According to theory, as the mass of the black hole decreases, the intensity of this radiation gets more intense, and as the process continues, the black hole loses mass, resulting in the acceleration of the rate of radiation. Eventually, the black hole sinks to a size where it can’t sustain itself, and it blows up, and this is the phenomenon that the MIT physicists think gave rise to that energetic neutrino.
At this point, much of this theory is sheer speculation. At this point, Hawking radiation has never been observed, though most physicists have confidence it exists. Further, nobody has observed PBHs either. Where would we find these PBHs? If they were created in the early history of the universe, they should be distributed more or less like the rest of the matter in the universe, but the MIT physicists are proposing that they could well be a principal constituent of the dark matter halos the surround most galaxies. While the existence of dark matter has been (more or less) firmly established, its nature is still a mystery. If this is the case, PBHs are potentially everywhere, and some of them could be quite close by.
There is a whole lot of speculation in this theory, but what makes it attractive is how many loose ends it could tie up. We need to see if it manages to hold together as it is scrutinized.
Comments are below the fold.
Top Comments (September 18, 2025):
From scooba:
Gregg Gordon's comment regarding Sabrina Haake's latest diary on ABC's suspension of Jimmy Kimmel's show gets to the heart of the matter in a witty, pithy way.
Top Mojo (September 17, 2025):
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