> But since there are 4x10^20 addresses per square inch of the > earth's surface Actually, there's 2.5 x 10^66 addressable locations per square inch (according to Planck) :-) - but an addressing scheme that is 10^45 or so times coarser should be good enough for most purposes. RM -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body