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  • Neutrinos are tiny, almost weightless particles that only interact via gravity and nuclear

  • decay. Because they don't interact electromagnetically, that is, with light, they literally can't

  • be seen!

  • In fact, detecting a neutrino is kind of like trying to catch a bullet with a butterfly

  • net – a beam of neutrinos will travel through lead for two years before it stops. (in comparison,

  • radiation from nuclear fallout can be blocked by about ten cm of lead)

  • So how do you detect a neutrino? One common way is to fill a big tank with water: we know

  • light slows down through water, and if a neutrino with enough energy happens to knock into an

  • electron, the electron will zip through the water faster than the light does! When this

  • happens, the electron gives off a weak glow called Cherenkov Radiation - it's kind of

  • like a sonic boom for light, and it allows us to detect the neutrino. The biggest neutrino

  • detector in the world is a balloon over the south pole that actually uses the whole antarctic

  • ice sheet as its tank of water!

  • Neutrinos also tell us that the universe is not the same as its mirror image. If you switch

  • left with right, clockwise with counterclockwise, almost all of physics, like gravity, electromagnetism,

  • and the strong nuclear force, is unchanged. However, the weird thing about neutrinos is

  • that in physics terms, they're all left-handed - their mirror image doesn't exist! So neutrinos

  • are the vampires of physics.

Neutrinos are tiny, almost weightless particles that only interact via gravity and nuclear

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What is a Neutrino?

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    Why Why posted on 2013/03/30
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