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from the and-hummingbirds-should-not-fly dept.
The apparent symmetry between matter and antimatter is puzzling scientists at the European Organization for Nuclear Research (CERN):
One of the great mysteries of modern physics is why antimatter did not destroy the universe at the beginning of time.
To explain it, physicists suppose there must be some difference between matter and antimatter – apart from electric charge. Whatever that difference is, it's not in their magnetism, it seems.
Physicists at CERN in Switzerland have made the most precise measurement ever of the magnetic moment of an anti-proton – a number that measures how a particle reacts to magnetic force – and found it to be exactly the same as that of the proton but with opposite sign. The work is described in Nature [open, DOI: 10.1038/nature24048] [DX].
"All of our observations find a complete symmetry between matter and antimatter, which is why the universe should not actually exist," says Christian Smorra, a physicist at CERN's Baryon–Antibaryon Symmetry Experiment (BASE) collaboration. "An asymmetry must exist here somewhere but we simply do not understand where the difference is."
Previously: Evidence Mounts that Neutrinos are the Key to the Universe's Existence
Matter-Antimatter Asymmetry Confirmed in Baryons
LHCb Observes an Exceptionally Large Group of Particles
Possible Explanation for the Dominance of Matter Over Antimatter in the Universe
(Score: 2, Informative) by dwilson on Thursday October 26 2017, @03:53PM (2 children)
As I recall, this has been considered and dismissed. If certain regions of space (within our observable universe) were entirely anti-matter, we would definitely know. The interface boundary between regions of anti-matter and regions of matter would be... energetic, to put it mildly. We'd see that, if nothing else. I want to say I know that because xkcd covered it in a what-if, but I really don't remember where I read it.
- D
(Score: 1, Informative) by Anonymous Coward on Thursday October 26 2017, @04:06PM
XKCD What If: Antimatter [xkcd.com], which links to Antimatter in the Universe : Constraints from Gamma-Ray Astronomy [arxiv.org] and When Clusters Collide: Constraints On Antimatter On The Largest Scales [researchgate.net].
It sounds like my conjecture about anti-matter regions probably isn't the case, but more sensitive instruments are always desired.
(Score: 3, Informative) by khallow on Thursday October 26 2017, @04:56PM
It would also have sharp peaks at the annihilation energy of electrons (and protons, neutrons, etc). That is incidentally how we know that minute amounts of antimatter are created by lightning [wikipedia.org].