Re: The Extinction Challenge

Technotranscendence (
Sat, 31 Jul 1999 07:52:29 -0700

On Friday, July 30, 1999 8:58 PM Billy Brown <> wrote:
> >> However, at a
> >> distance of 1 light-year (9x10^12 kilometers), the energy density drops
> to
> >> less than one erg per square meter. That isn't even enough energy to
> >> damage electronics, let alone harm people.
> >
> > Energy density is not a realistic measure of danger.
> 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, and any space
> capable of surviving a solar storm will likewise be unharmed. If it were
> all neutrinos an average human would stop a grand total of maybe 10^-17 %
> that flux, which amounts to around 10^-7 electron volts - in other words,
> less than one interaction.
> Do I really need to write up a complete treatment of all the calculations
> here? It doesn't matter what exotic form you want the energy to arrive
> because there simply isn't enough of it to do anything. The target
> civilization will be exposed to much higher levels of every type of
> radiation (including neutrinos) simply by living near their own sun.

I tend t oagree, but I've not done the calculations... I'd also, though, be worried about secondary effects. E.g., if a local supernova increased the heat influx on the surface of comets, thereby changing their orbits enough to create a danger to us. Granted, this is far-fetched and, I bet, any changes of this sort might cut it either way -- might put us out of danger more than in danger.

Though, just intuitively, without doing any statistical orbits on this, imagine the cometary bodies nearer the supernova (the the "windward" side of the solar system) being push, ever so slightly toward the sun, changing more of the orbits so that they might enter the inner solar system. This might create a hazard that would play itself out over thousands of years.

Anyway, I'm not lying awake nights worrying about this...:)

Daniel Ust