>> Of course, it is probably plate tectonics – and the large moon – that has made it habitable...
>
> How so, Jim?
I only partially understand the orbital mechanics, but the large moon apparently stabilizes the Earth's rotation axis. If it were varying more widely, and over shorter periods, climate shifts would be more rapid and more severe, with few, if any, long stable periods for species to "mature" before they were wiped out by major climate shifts.
It appears that Earth is the only planet in this system that has plate tectonics. Even our "twin" — Venus — does not. The moving crustal blocks re-cycle the lithosphere, produce very "friendly" zones at regions of sea-floor spreading (lots of nutrients any lots of energy available: this may be where life began here), and slowly, over millions of years, creates and then slowly alters or destroys refugia for life to develop in — nearly textbook circumstances for driving the evolutionary process.
Volcanism is also an essential process for making some metals and minerals easily available at the surface, rather than leaving them buried under miles of crust.
[I am only an educated amateur at this. I've found the processes fascinating, and have read up on them sporadically over the decades.]
--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jim Saklad mailto:jimdoc@icloud.com
------------------------------------
------------------------------------
------------------------------------
Yahoo Groups Links
<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/iPad/
<*> Your email settings:
Individual Email | Traditional
<*> To change settings online go to:
http://groups.yahoo.com/group/iPad/join
(Yahoo! ID required)
<*> To change settings via email:
iPad-digest@yahoogroups.com
iPad-fullfeatured@yahoogroups.com
<*> To unsubscribe from this group, send an email to:
iPad-unsubscribe@yahoogroups.com
<*> Your use of Yahoo Groups is subject to:
https://info.yahoo.com/legal/us/yahoo/utos/terms/