Re: The Extinction Challenge

John Clark (
Wed, 4 Aug 1999 13:34:50 -0400

Hash: SHA1 On Tuesday, August 03, 1999 Wrote:

>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.

You make a good point. I haven't double checked your numbers but they sound about right to me. I have only 2 minor quibbles, neither effect the strength of you argument by much.

  1. I was figuring a supernova about 8 light years away not 2.
  2. A dangerous radiation dose is much less than a lethal one.

Nevertheless I now think that neutrinos from a supernova is of no danger to any civilization, you'd have to be so close you'd already be vaporized by more conventional radiation. Neutrinos aside we'd still be in very serious danger from a supernova 2 light years away, or even 8, but a super civilization could survive.

The thing that fascinates me about an intense neutrino beam is that the is no defense even a super civilization with full Nanotechnology could mount against it. If beams of that power actually exist it's clear that conventional supernovas didn't make them. I've seen some exotic models of rare Hypernovas and black hole formation that might do the trick, but unlike supernovas there is no experimental conformation that they actually produce the number of neutrinos that theory says they should.

John K Clark

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