URTH 

Date: Fri, 29 Mar 2002 14:04:41 0600 Subject: Re: (urth) Blue moon From: Adam Stephanideson 3/28/02 11:44 PM, Roy C. Lackey at rclackey@stic.net wrote: > From: Adam Stephanides > Date: Thursday, March 28, 2002 3:19 PM >> Suppose that they do have independent orbits. Conjunction is every six >> years, so six Blue years equal either five or seven Green years. Hence the >> time between conjunction and Gagliardo's observation is either fivesixth > or >> sevensixth of a Green year. In either case, the distance between >> conjunction and the position Green is in at Gagliardo's observation (call > it >> position A) is the distance Green travels in onesixth of a Green year. >> >> Now at conjunction Green is 105,000 miles from Blue. At position A Green > is >> 250,000 miles from Blue. Hence position A cannot be more than 355,000 > miles >> from conjunction (actually, we could get an even better estimate, but it's >> not necessary). If Green's orbit is approximately circular, then simple >> geometry (think a regular hexagon) shows that Green's distance from the >> Short Sun itself can't be more than 355,000 miles, with Blue's distance not >> much more: that is, less than twice the distance from the Earth to the > Moon. >> >> This is impossible. [snip] > > Huh? I don't follow that. Gagliardo's numbers don't say anything about the > length of either body's solar orbit that I can see. His numbers indicate > that at your position A the two bodies have _diverged_ by about 145,000 > miles since conjunction. In that one year interval both bodies have also > circumnavigated the sun. Two years later Blue and Green will have attained > maximum separation, a distance af about 540,000 miles, then start gradually > getting closer together until the next conjunction. > > In other words, for the two bodies to be in independent orbits, those orbits > would have to be almost congruentalmost, but not quite. Think of the two > bodies as twin planets, traveling almost in tandem around the sun. The > attraction of one body for the other causes minor changes in their orbital > velocities, which average out over a sixyear cycle, but account for the > fluctuation in distance between the two bodies during the cycle. Or am I > missing something so obvious I can't see it? I was treating Blue and Green as analogous to Earth and Venus: completely independent orbits which remain fixed (i. e. don't oscillate). What you describe is more like mantis's twin moons chasing each other. But I think it's probably hopeless to try and figure out what, if anything, Wolfe had in mind. Adam 