[ExI] Eternity in six hours: intergalactic spreading of intelligent life and sharpening the Fermi paradox

[BillK]

On Tue, Sep 10, 2013 at 10:06 AM, Tomaz Kristan  wrote:
> Instead of just recycling their initial star's energy, wouldn't they want to
> recycle all around?
> This self limitation is very unlikely. Even much less for "all those
> millions civs everywhere".
>
> The Rare Earth is the only sane explanation for our apparent solitude.
>
>

The Rare Earth hypothesis is not just one theory. It is a complicated
system with many alternatives.
(And many critics, of course).

<http://en.wikipedia.org/wiki/Rare_Earth_hypothesis>

One option is that civilisations might be plentiful, but spread so far
apart that contact between civs is very unlikely. (The universe is
really, REALLY big).

Another time-dependent option is that we are at the right age in the
universe for intelligence to have developed. And intelligent life is
just starting to appear throughout the universe, all at almost the
same time - within a few million years of each other.

I find the hard-line 'Rare Earth' option rather unbelievable. That
everything must be exactly the same as our Earth for life to appear
seems extreme circular reasoning.

BillK