Antarctica Scientists Confirm Existence of Cosmic Neutrinos
Extragalactic.
hough they don’t interact much with matter, occasionally one will hit an atomic nucleus on Earth. When that happens the neutrino generates a particle called a muon. That’s what scientists look for when seeking neutrinos — the muons move faster than the speed of light in a solid (ice in this case) and generate light waves, like the wake of a boat in water, called Cherenkov radiation. They also show the paths of the neutrinos. (The speed of light is constant in a vacuum, but it is slower in a medium like ice or glass — this is what causes refraction. So the muons aren’t actually breaking the speed of light limit).
The IceCube project found neutrinos from outside our galaxy in 2013, but to confirm that detection the researchers, led by a team at the University of Wisconsin-Madison, had to make sure these neutrinos weren’t coming from sources within our own galaxy (such as from the sun). To do so, they looked for neutrinos with similar energies that were coming from all directions at the same rate, meaning they are independent of the Earth’s rotation and orbit around the sun — the only way that can happen is if the source is outside the galaxy.
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