RE: The Extinction Challenge

Billy Brown (
Sat, 31 Jul 1999 11:53:18 -0500

John Clark wrote:
> Billy Brown <> Wrote:
> >If it were all neutrinos an average human would stop a grand total of
> >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.

Actualy, yes, that is exactly what I mean. It's a only rough approximation, of course - since you don't seem to believe it, I'll get a more detailed computation.

> >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.

  1. People get hit by single X rays all the time and survive - energy density is the major determinant of the probability that you will actually get one of those unlucky hits. Rendering a sentient race extinct requires you to approach 100% mortality, which means you need a very high probability, which in turn means you need a significant amount of energy.
  2. What on Earth makes you think it is realistic to expect cancer to be a significant problem for a spacefaring civilization? Do you seriously think that we could spend another thousand years researching the problem without finding reliable cures? With sublight space travel, that is the kind of timespan we need to be thinking about.

> >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.

Yes, I do. If you think I'm wrong, show me the error in my calculations.

> >Do I really need to write up a complete treatment of all the
> calculations here?
> Yes, I rather think you do.

OK - but it will have to wait until after Extro. I'll post the URL when I get the web page up.

Billy Brown, MCSE+I