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Why didn't the universe annihilate itself? Neutrinos may hold the answer:
Alysia Marino and Eric Zimmerman, physicists at CU Boulder, have been on the hunt for neutrinos for the last two decades.
That's no easy feat: Neutrinos are among the most elusive subatomic particles known to science. They don't have a charge and are so lightweight—each one has a mass many times smaller than the electron—that they interact only on rare occasions with the world around them.
They may also hold the key to some of physics' deepest mysteries.
In a study published today in the journal Nature, Marino, Zimmerman and more than 400 other researchers on an experiment called T2K come closer to answering one of the big ones: Why didn't the universe annihilate itself in a humungous burst of energy not long after the Big Bang?
The new research suggests that the answer comes down to a subtle discrepancy in the way that neutrinos and their evil twins, the antineutrinos, behave—one of the first indications that phenomena called matter and antimatter may not be the exact mirror images many scientists believed.
[...] In their most recent study, the researchers hit pay dirt: These bits of matter and antimatter seem to behave differently. Muon neutrinos, Zimmerman said, are more inclined to oscillate into electron neutrinos than their antineutrino counterparts.
The results come with major caveats. The team's findings are still quite a bit shy of the physics community's gold standard for a discovery, a measure of statistical significance called "five-sigma." The T2K collaboration is already upgrading the experiment so that it can collect more data and faster to reach that mark.
But, Marino said, the results provide one of the most tantalizing hints to date that some kinds of matter and antimatter may act differently—and not by a trivial amount.
[...] "There are still things we're figuring out because neutrinos are so hard to produce in a lab and require such complicated detectors," Marino said. "There's still room for more surprises."
Journal information: The T2K Collaboration, Constraint on the matter–antimatter symmetry-violating phase in neutrino oscillations, Nature (2020). DOI: 10.1038/s41586-020-2177-0
(Score: 1) by anubi on Friday April 17 2020, @10:17AM (5 children)
How do we know other galaxies are all matter?
Is an antiphoton distinguishable from our photons?
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]
(Score: 2) by PiMuNu on Friday April 17 2020, @12:10PM (3 children)
> How do we know other galaxies are all matter?
There is no evidence of annihilation at the matter:antimatter boundary.
Nb: Just as a side note, no one knows if gravity attracts or repels antimatter.
> Is an antiphoton distinguishable from our photons?
A photon is the same as an antiphoton .
(Score: 2, Interesting) by shrewdsheep on Friday April 17 2020, @02:49PM (2 children)
I have always wondered about this (IANAP). Assuming there was a small matter/anitmatter asymmetry in the beginning this should have quickly separated matter/antimatter on separate sides of the universe. In the meantime, the universe has dramatically expanded which would leave enough space between the matter and antimatter part of the universe, at least in my book. A forteriori, any potential boundary should be cleared of matter very quickly, so I do not get that point. Please elaborate.
(Score: 2) by PiMuNu on Friday April 17 2020, @03:44PM (1 child)
You are right. Indeed, we can't see most of the universe (we are outside it's event horizon). So half of the universe could be made of matter and the other half antimatter, with the interface not visible from the earth. There is some evidence for the universe being different in different directions (e.g. a SN article a few days ago).
(Score: 0) by Anonymous Coward on Friday April 17 2020, @05:01PM
If it were 1/2 and 1/2, you'd expect a few comets now and again made of anti-matter. That would be popcorn-worthy.
(Score: 1, Interesting) by Anonymous Coward on Friday April 17 2020, @04:06PM
Photons are their own anti-particle, and we recently had an experiment that confirmed that the light spectra from anti hydrogen is the same as from hydrogen. Which means that you can't tell that a star is made of anti-hydrogen by looking at it.
My understanding is that the lack of annihilations at the boarder is our only proof of the idea that they visible universe is all matter.
That said, physicists and astronomers insist this is strong proof.