[ExI] SETI reviews the Drake equation

John Clark johnkclark at gmail.com
Sat Feb 2 17:09:28 UTC 2019

On Wed, Jan 30, 2019 at 2:28 PM BillK <pharos at gmail.com> wrote:

By Seth Shostak, Senior Astronomer
> <https://www.seti.org/drake-equation-could-it-be-wrong>

> *> even travelling at, say, only one-tenth the speed of light, it takes
> more than a million times more energy to establish a colony around another
> star than required to establish one of the same size near their own.*

At one-tenth the speed of light it would take about 500,000 years to send a
Von Neumann probe to the most distant sun in the Milky Way from the Earth,
but no need to go that fast, at 1/1000 of light speed, not much faster than
what we can do right now, it would only take 50 million years and that is a
trivial amount of time by cosmological standards.  Also, the energy
required to do that depends not only on the speed of the probe but also on
its mass, and a Von Neumann probe could have less mass than a grain of
sand. If ET had actually sent such a probe into our galaxy or into any
other it would be obvious, but we see no hint of it and all we hear is a
great silence.

John K Clark
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