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Just how often are you hit by a neutrino?

Just a little snippet of information I picked up at the American Physical Society meeting in Washington, DC, this weekend:

Chris Walter of Duke University says that the probability of a neutrino interacting with your body at some point in your life is about 1 in 4. So look around your friends--how many of them have been hit by a neutrino?

Keep in mind that neutrinos are flooding through you generally without interacting--about 100 trillion per second. That translates to something like 2.5 x 1021 neutrinos pass through you in your lifetime.

With a few simple estimates, we can convert that to say that the chance of a particular neutrino actually interacting with you is about 1 in 1 trillion trillion. That number is so extreme I can't even really imagine it so I'll just wonder for the rest of my life whether I've been one of the people lucky enough to be hit by a neutrino.