Re: >H FYI:SCIENCE-WEEK July 3, 1997 (fwd)

Anders Sandberg (
Fri, 4 Jul 1997 11:31:09 +0200 (MET DST)

On Thu, 3 Jul 1997, The Low Golden Willow wrote:

> On Jul 4, 7:40am, Eugene Leitl wrote:
> } Gamma rays at the density of lead (which are opaque to gamma ;), flying
> } towards us at about 0.99 c. So somebody is throwing chunks of solid gamma
> } at only slightly subliminal velocities. As even puny supernovas generate
> Gamma rays... these would be photons, yes? "Slightly subliminal"? I'm
> having a problem here.

Subliminal probably refers to velocities slightly below the speed of
light (subliminal = beneath the threshold, usually used in

Yes, gamma rays are photons. Although pair production might turn them
into electron-positron pairs if they get close to another particle.

> Urrrn. If supernovae are deadly in 100 ly, shouldn't Sirius be frying
> us in a few million years?

Sirius? I'm not sure, but isn't it too small to become a supernova?
Besides, in a few million years we will be farther away (at least a
few more ly). According to my files there are just 10 bright A stars
within 50ly: Altair (A7), Castor A (A1), Castor B (A1), Castor C
(A5), Castor D (A5), Denebola (A3), Formalhaut (A3), Iota Ursae
Majoris A (A7), Sirius A (A1) and Vega (A0). There is also Arcturus,
a K2 giant. None of these strikes me as particularly dangerous, but I
might be wrong.

> Cross-posted to extropians for maximum criticism.

Anders Sandberg Towards Ascension!
GCS/M/S/O d++ -p+ c++++ !l u+ e++ m++ s+/+ n--- h+/* f+ g+ w++ t+ r+ !y