On Thu, 22 Aug 2002, der Mouse wrote:

> My back-of-the-envelope calculation says that the greatest speed two
> machines are moving at with respect to one another because of the
> rotation of the earth is about 158 metres per second.  Since I made
> simplifying assumptions (eg, I assumed the earth is a sphere), this is
> probably a bit out, but is likely the right order of magnitude.
> 
> I note that Larry Niven disagrees; in _The Theory And Practice Of
> Teleportation_ is a line implying, if I recall it correctly, that the
> correct figure is half a mile a second - and Niven usually has his
> facts right.  Can someone check my work?

To within a few 10s of %...  Earth = 24,000 miles circumference, rotates
once per day (+/- a couple of seconds per year ;) => 1000 mph.

1000 / 60 / 60 = .2777 miles per second.

Double for relative motion in opposite directions = .55555 miles per
second for diametrically opposed points on the equator.

If I goofed, I'm sorry -- I couldn't find an envelope and had to do it in
my head instead.

Ian