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<div class="moz-cite-prefix">On 2013-11-22 09:28, Kelly Anderson
wrote:<br>
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cite="mid:CAPy8RwYyNtTvuHOQoK1jaUMfmT2vejO-9OB_VZm6yyCBTQTyjg@mail.gmail.com"
type="cite">
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<div class="gmail_quote">On Wed, Nov 20, 2013 at 5:36 AM,
Anders Sandberg <span dir="ltr"><<a
moz-do-not-send="true" href="mailto:anders@aleph.se"
target="_blank">anders@aleph.se</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">OK, now
I have a better writeup:<br>
<a moz-do-not-send="true"
href="http://www.aleph.se/andart/archives/2013/11/greetings_from_doubleearth.html"
target="_blank">http://www.aleph.se/andart/archives/2013/11/greetings_from_doubleearth.html</a></blockquote>
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<div>That was an incredibly detailed writeup. Thank you
Anders. So if I understand, the physics of a "twice as
large" earth lead to no continents? Does that assume the
same proportion of water as earth was formed from?</div>
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<br>
Thanks! Yes, I assumed the same proportion of water went into the
formation of Dry. Wet of course is much wetter. <br>
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cite="mid:CAPy8RwYyNtTvuHOQoK1jaUMfmT2vejO-9OB_VZm6yyCBTQTyjg@mail.gmail.com"
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<div> It kind of seems like if there were less water for
some reason, you still might get continents, but perhaps
I'm missing some rule of thumb that suggests the ratio of
water is similar everywhere???<br>
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<br>
We don't know for certain. When a solar nebula coalesces into
planets, the innermost parts get baked by the sun and gas and
volatiles are blown away. Outside the "iceline" a few AU out lots of
water remain, and planets that migrate inwards during formation will
turn into inner system wet planets - but the details of early
migration are complicated. <br>
<br>
I think the likely answer is that Earth formed roughly where it is,
and has a typical composition. So if it had been bigger it would
have been like my Dry double-Earth. In theory, a Dry that formed
from material even closer to the sun and then got moved out a bit
(say by a passing hot Jupiter) might be a heavy world with "normal"
ocean sizes.<br>
<br>
<br>
<pre class="moz-signature" cols="72">--
Dr Anders Sandberg
Future of Humanity Institute
Oxford Martin School
Oxford University
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