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Message: <blockquote data-quote="Umbran" data-source="post: 8427880" data-attributes="member: 177">Um, when we get to tides for this large, but not dense, world, things will get complicated.On Earth, we see tides in the ocean, but the tidal forces affect the entire planet.  For Earth and its moon, we don't notice the effect on the rock of the planet on a day to day basis, because there's a whole lot of strong rock.  The ground only flexes a bit (about one foot, actually), while the water, being fluid, moves a lot more.But, this low-density, large planet, is a different beast.  If we are talking about a thin shell - that one foot of movement is a large flex for a 30-foot thick shell like the dyson sphere discussed above. This is incorrect.  In our own solar system, the heavy worlds are farther from the sun, but that's not a general rule, by a long shot.[spoiler="Here's a graph of exoplanet radii and their distance form their stars"][ATTACH=full]145297[/ATTACH][/spoiler]In general, on this scale, for the most part we can use radius as a proxy for mass - it is hard to be 10 times bigger and not be heavier - and we won't be too far off.The Earth is down at the lower left area of the graph (one earth radius, and 93 million miles from the sun).  You'll note that Jupiter-sized worlds (along the top of the plot) exist all along the spectrum from around 1 million to a hundred million miles from their parent star.There is a scarcity of middling sized worlds near their stars (in the "Neptune Desert" region.  But big and small worlds are found all over the place.</blockquote>

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