Orbit 0
In reply to #5184 Cold suns & soft science: UWPs revisted by james vassilakos
James Vassilakos writes: >in book six of the classic rules). Now the question really is, how >much faith can we put in this "orbit 0"? Thinking like a humanities >major, I see no reason why a planet shouldn't be able to get as >close to its star as it wants to (barring the vaporization distance, >which isn't going to be very lengthy in this case). There's something known as the "Roche Limit". Anything closer than that that will be subject to tidal forces stronger than its own gravity. Which means that satellites *cannot* form inside the Roche Limit of the parent body. And if a body is somehow moved to an orbit inside the Roche limit, it has to have enough structural strength to resist the tidal force. And they increase with the *cube* of the distance as you approach the parent body. >You've got to remember that "orbit 0" is a figment of somebody's >imagination. There are no rail-road tracks out there in space >dictating where a planet must orbit. Orbit numbers are a convenience >instated by the rules. Nothing more. Well, there actually *are a lot of limits on available orbits based solelyt on orbital dynamics. For instance, orbits with periods in a simple integer relationship to each other are unstable because the "tugs" they give each other reinforce. Simple fractional realtionships (like 2/3, 4/5 etc) can do it too. This is why there are areas in the asteriod belt where there aren't any asteroids, they'd have orbits synched with Jupiter this way. Ditto for Saturns rings, the gaps are caused by resonances with some of the satellites. >Even if you argue that they are based on astronomical observations >(the ratio of orbital distances and so forth), you still have to >realize that these observations have been taken from one star >system, ours, and that we haven't yet had a chance to verify the >theory with data on other star systems. We have not just the planets orbiting the sun, but the asteroids and the various moons orbiting the planets. That's a *lot* of observational data. Leonard Erickson [email removed] CIS: [70465,203] [email removed] FIDO: [email removed] [email removed] (preferred) - -- uucp: [email removed] Internet: [email removed]