On 28/09/2018 10:46, Paul Schlyter wrote:
On Wed, 26 Sep 2018 12:07:27 -0700 (PDT), Gary Harnagel
wrote:
As I said, it only takes ONE civilization to make it.* It can then
spread
to other galaxies in a few million years, a very short time in the
universe=

Only in fantasy science fiction like Star Trek is this possible.

You are hopelessly overoptimistic. The typical distance between galaxies
is millions of light years or more. Therefore you are saying that any
civilisation would with great probability learn interstellar travel at
or near light speed. Are you even aware of the difficulties involved?

It may well be the case that the distances between stars are so vast
that no civilisation can realistically travel between them unless they
happen to be in a privileged place with a very high density of nearby
stars. Robotic Fermi probes ought to be possible - they don't need to
sustain life and can wake up only when in proximity to a star.

It is an interesting question of how small a probe we could make with
existing technology to get to Proxima Centuri and send information back.
Milner and Hawking proposed one way to get there in about 20 years if
you accept the assumptions behind their methodology.

https://www.smithsonianmag.com/smart...tem-180958745/

For instance, colliding with a grain of sand near light speed would mean
the end of your expedition.

And you will get cooked by the blue shifted cosmic background radiation
as well. The faster you travel the better your heat shield has to be.

--
Regards,
Martin Brown