"Even though the majority of the Universe is dark in the sense that we haven't figured out how to directly detect it - with 95% of the cosmic energy density comprised of dark energy and dark matter - the 5% that comes in different forms of matter and radiation is profoundly significant. It makes up us, the planets, stars, and galaxies, as well as starlight, the plasmas and neutral gas clouds found within and beyond galaxies, and everything else we can observe."
"As far as we've been able to determine, the proton is stable. Experimentally, we've placed a lower limit on its lifetime of a whopping 10 34 years: around a septillion times the present age of the Universe. And yet, the question of whether the proton decays, and if so, what its lifetime is, is at the core of one of the greatest mysteries in all of theoretical physics."
Protons make up the bulk of visible-matter mass and appear experimentally stable, with current lifetime limits exceeding 10^34 years. Proton decay would signal baryon number violation and new physics beyond the Standard Model, including many grand unified theories that predict distinct decay channels such as p → e+ π0 or p → ν K+. Detecting such decays demands enormous target masses, ultra-low backgrounds, deep underground locations, and precise particle-identification technologies in long-duration experiments. Directly forcing proton decay is not possible with known technology; only sustained, large-scale observation can reveal such exceedingly rare events.
Read at Big Think
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