Earth's atmosphere protects us from the continuous barrage of high-energy cosmic rays that reach our planet from space. It keeps us from living in a giant microwave, in a sense. While these rays have many sources—black holes, supernovae, quasars, gamma-ray bursts, the Big Bang itself—one is of particular interest: dark matter. And hanging off the side of the International Space Station one finds the Alpha Magnetic Spectrometer, part of an experiment designed to hunt for dark matter by observing the production of antimatter in our atmosphere.
Indeed, newly crunched results from the AMS detector are now showing even more promising hints of dark matter from these showers of cosmic rays.
In the dark matter hunt, physicists are particularly interested in the pairs of matter and antimatter particles that are created when superfast-moving particles collide with bits of matter or energy in the atmosphere. Antimatter is a natural result of the particle creation that occurs when two massless particles (like photons) collide to form two massive particles (an electron and positron).
Normally, the antimatter part of the equation is annihilated immediately when it meets some bit of normal matter, resulting in nature's most efficient, near-perfect release of energy. But up in orbit, at the very edge of the atmosphere, it's possible to count antimatter particles before they blow up. Crucially, it's possible to determine if there are extra antimatter particles beyond what should be expected from detectable cosmic rays. This would indicate that there is some additional source of rays so far unaccounted for.
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