Re: The Extinction Challenge
Tue, 3 Aug 1999 02:54:57 EDT

In a message dated 8/1/99 19:02:45, wrote:

> Wrote:
>>But even by your figures, a 100 kg mass would expect 2 x 10^7 hits
>>from a supernova 2 ly away. In a body of many billions of cells,
>>that's quite trivial. Only about 1 cell in a 1000 will take a hit,
>>and the vast majority of hits don't do anything significant.
>An Alpha particle will kill or mutate any cell it hits, a rare neutrino that
>would be almost as deadly.

Well, I looked up some of these numbers.

A supernova neutrino has an energy of 5 to 40 MeV. An ev is 1.6 x 10^-12 ergs, so a sn neutrino is up to 6.4 x 10^-5 ergs. The rate under discussion yields 200 neutrinos absorbed/gram, or 1.3 x 10^2 ergs/gram, which is 1.3 x 10^-4 rads. (0.00013)

A 50% lethal dose at Hiroshima was about 400 rads. Alpha particles are more hazardous and a 50% lethal dose would be about 20 rads.

The radiation dose from the 2 ly-away supernova is thus less than 1/100000th of a 50% lethal dose, even if neutrino energy is a damaging as alpha particle energy. You would not even be able to detect a change in the cancer rate. It's trivial.