[extropy-chat] Re: Animals

Eugen Leitl eugen at leitl.org
Wed Feb 18 17:15:57 UTC 2004

On Wed, Feb 18, 2004 at 03:38:15PM +0000, Christian Weisgerber wrote:

> > Mid-Life Crisis for the Earth
> > 5.6 Gyr (1.1 Gyr from today):
> >     * Sun 10% brighter: ~1.1 Lsun
> >     * Cause a moist greenhouse effect on Earth, driving away most of the
> >     * water in the air. 
> Oh, okay.  That is of course a long shot from the previously claim
> that "the sun's expansion would destroy life on Earth in 500 million
> years".

Not really. Half a gigayear is ballpark figure. And of course this ignores
giant impacts, which will produce major extinction events and radical loss of
biodiversity (if not even higher life). You need a lot of time to rebound
from that. Arguably, more time that this biosphere's expiration date.
> > I have no idea how reliable is this. Even 1% of solar constant change
> > typically can wreak havoc to climate, so 10% increase sounds pretty
> > catastrophic to me.
> Yes, but it's a slow, continuous process.  Anybody have any figures

No, luminosity quite suddenly starts going up once you go off the main sequence on
Hertzsprung-Russell. It's basically constant while you're still in hydrogen
burn. I was looking for a luminance curve vs. age for a
Sol-mass star, but haven't found any on the fly.

Since I'm at work, the best I can do is

> how much hotter the sun has grown over the time we've had multicellular
> life on earth?

-- Eugen* Leitl <a href="http://leitl.org">leitl</a>
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