From: "JACK L. URETSKY (C) 1996; HEP DIV., ARGONNE NATIONAL LAB, ARGONNE, IL 60439" <JLU@hep.anl.gov>
Date: Thu, 20 Jun 1996 20:03:11 -0500 (CDT)
Hi Jim Green-
I understand "empty space" to empty of matter.
The number that I keep in mind for the inter-stellar medium
is about 1 atom/cc. That's a pretty hard vacuum..
Regards,
Jack