RE: Kardeshev is pre-Spike thinking

From: Billy Brown (
Date: Wed Jun 07 2000 - 16:53:17 MDT

Eugene Leitl wrote:
> Not only galaxy, but our galactic neighbourhood (and beyond?). The
> only good explanation for the Fermi paradoxon is imo still very thin
> life nucleation density, and more or less simultaneous hatching
> (heavier elements needing nucleosynthesis). Meaning, we're outside of
> expansive aliens' light cone.

Agreed, but note that this also requires that FTL travel be impossible even
to determined SIs. If you think SIs might be capable of FTL travel you need
an even more extreme sparsity of civilizations - really fast FTL would imply
that ours is the first civilization to achieve the capacity for expansion
into space.

> Since expansive aliens expand with
> speeds near to relativistic, there is obviously very little warning,
> before the expansion front hits out system.

Well, 'very little' is a relative thing. An expansion rate of 99.9% C over a
distance of 10^7 LY still gives us 10,000 years of watching the expansion
move our way. We would only be caught by complete surprise if the expansion
front moved faster than C.

Billy Brown

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