<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div>On Jan 25, 2016, at 8:13 AM, John Clark <<a href="mailto:johnkclark@gmail.com">johnkclark@gmail.com</a>> wrote:</div><div><br></div><blockquote type="cite"><div><div dir="ltr"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><span style="font-family:arial,sans-serif">On Sun, Jan 24, 2016 at 7:41 AM, Anders Sandberg </span><span dir="ltr" style="font-family:arial,sans-serif"><<a href="mailto:anders@aleph.se" target="_blank">anders@aleph.se</a>></span><span style="font-family:arial,sans-serif"> wrote:</span><br></div><div class="gmail_extra"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<p class="MsoNormal"><a href="http://www.sciencemag.org/news/2016/01/feature-astronomers-say-neptune-sized-planet-lurks-unseen-solar-system" target="_blank">http://www.sciencemag.org/news/2016/01/feature-astronomers-say-neptune-sized-planet-lurks-unseen-solar-system</a><u></u><u></u></p>
</div></blockquote></span><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;display:inline">> </div>Would it actually count as a planet? I seem to recall that the
Pluto-killing definition includes "has cleared its orbit of
planetesimals". <br></div></blockquote><div><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif"><font size="4">I've never quite understood that definition. Neptune hasn't cleared its orbit of Pluto so why is Neptune a planet? </font></div></div></div></div></div></blockquote><div><br></div>This one I agree with you on. And let's say by some change another currently accepted planet's orbit became uncleared -- say the asteroid belt shifted into Mars orbit -- would it be scratched from the list of planets?<div><br></div><div>And how clear is clear? There are Mars-crossing asteroids now, to stick with my example.</div><div><br></div><div>I don't see why the decision couldn't have been along the lines of:</div><div><br></div><div>There are three types of planets we now know of:</div><div>1. Rocky ones like Earth and Mars,</div><div>2. Gassy ones like Jupiter and Neptun, and</div><div>3. Icy ones like Pluto.</div><div><br></div><div>I don't see why 1 plus 2 alone must be planets, must be where Nature made the joints, while 3 is not.</div><div><br><div><div style="line-height: normal;"><span style="line-height: 20px; background-color: rgba(255, 255, 255, 0);">Regards,</span></div><div style="line-height: normal;"><span style="line-height: 20px; background-color: rgba(255, 255, 255, 0);"><br></span></div><div><div style="line-height: normal;"><span style="line-height: 20px; background-color: rgba(255, 255, 255, 0);">Dan</span></div><div style="line-height: normal;"><span style="background-color: rgba(255, 255, 255, 0);"> Sample my Kindle books via:</span></div><div style="line-height: normal;"><a href="http://author.to/DanUst" style="background-color: rgba(255, 255, 255, 0);"><font color="#000000">http://author.to/DanUst</font></a></div></div></div></div></body></html>