Re: The Extinction Challenge

John Clark (
Sat, 31 Jul 1999 00:48:21 -0400

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Billy Brown <> Wrote:

>If it arrives as IR or UV it is completely harmless.


>If it arrives as visible light it is not nearly as bright as the sun.


>X-rays or gamma-rays will be completely blocked by a planetary atmosphere

True, but they and the high speed electrons and protons that also come from the supernova would produce radioactive isotopes in the atmosphere that would be no fun at all. The ozone layer would go to hell too.

>and any space habitat capable of surviving a solar storm will likewise be

That is very far from obvious.

>If it were all neutrinos an average human would stop a grand total of maybe
>10^-17 % of that flux, which amounts to around 10^-7 electron volts -
>in other words, less than one interaction.

I have no idea what you're talking about. You seem to saying that a human body would not absorb even one neutrino from a nearby supernova, but you can't possibly mean that.

>It doesn't matter what exotic form you want the energy to arrive in,
>because there simply isn't enough of it to do anything.

To repeat myself, energy has little to do with danger, just one X ray photon could kill you if it hits in the right place and in fact that very thing is a major, perhaps the major, cause of the most feared disease of the 20'th century that kills millions of people every year.

>The target civilization will be exposed to much higher levels of
>every type of radiation (including neutrinos) simply by living near
> their own sun.

Once more I must say that you can't possibly mean what you seem to be saying.

>Do I really need to write up a complete treatment of all the calculations here?

Yes, I rather think you do.

John K Clark

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