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This Week: Everyday Humanism

Apocalypse Later

This week, we talk to Zeke Piestup, the only journalist permitted to hang out with the late Harold Camping in the leadup to his failed May 21st rapture.  He is the director of Apocalypse Later, a documentary about late radio preacher Harold Camping, who claimed the Bible guaranteed the second coming of Jesus on May 21, 2011.

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Neil H July 21, 2014 at 12:59 pm

Technically speaking it is the charge on alpha and beta particles that limits their penetrating power. Their mass does correlate the total damage inflicted since heavier things tend to have more energy to deposit, but the energy is deposited over a shorter path due to the net electric charge on alphas and betas allowing them to interact with any atom they pass near to rather than needing a direct hit like gammas and neutrons. As mentioned neutrons need a significant amount of material (ideally high density but low atomic weight) to be blocked but betas can easily be blocked by a few millimeters of aluminium, or anything else you have on hand.
One interesting effect of this is that alphas and betas will be guaranteed to stop after a certain distance in a given medium, due to interacting at range, but gammas and neutrons suffer an exponential fall of with increasing barrier thickness which never technically reaches zero, the maths for attenuation of these pair is essentially the same as radioactivity falling off with time due to half lives.

Other than that one small detail spurring a long winded knowledge dump, that was a pretty good summary.

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