Re: The Extinction Challenge (fwd)

John Clark (
Mon, 2 Aug 1999 16:33:32 -0400

Hash: SHA1

>> An Alpha particle will kill or mutate any cell it hits, a rare neutrino that hits
>> would be almost as deadly.

     >Robert J. Bradbury <> On Monday, August 02, 1999
     >John, I'm almost certain this is incorrect.


> Radiation doses are moderated by virtually all intervening mass.


>The denser the mass the quicker the moderation. An alpha particle
>is a helium nucleus and gets moderated much quicker than other
>forms of radiation (because it is bigger and interacts more quickly).

A few inches of air or the thinnest tissue paper will stop an Alpha particle that's why Plutonium, a moderately strong emitter of Alpha particles, is pretty harmless as long as it's in one big lump (but not too big!) outside the body; only the surface material can gives off free particles and even those are stopped after a short distance. Plutonium only becomes the most deadly poison on the planet when it's in the form of a fine powder and is ingested into the body, either by eating it or breathing it into the lungs, because every Alpha particle then emitted will hit a living cell someplace and kill it, or far worse, mutate it. No cell can escape the massive damage of an alpha particle.

John K Clark

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