# a dog's life *The Urth list — 1 messages, 1 voices, 27 Mar 1998* > Exported from an unofficial mirror of a public mailing list. Copyright > in each message remains with the person who wrote it. > Email addresses are obscured as `user at host`, the form the original > archive published. This file was rebuilt from parsed fields rather than > retained headers, so it is faithful in content but not byte-exact. --- ### m.driussi *27 Mar 1998, 02:53* Reply: Item #3679491 from URTH at LISTS.BEST.COM@INET01# Hello Damien Broderick, and welcome aboard! Way back when (deep in the archives?), I was arguing that the world of "Tracking Song" was Mars-like if not Mars: the lesser gravity, the two moons. I also thought that the sky mirror was really a sky mirror, put there in geostationary orbit by the space beings to reflect more sunlight onto the apparently ice age-locked world in order to warm the surface and melt the ice. Fairly standard terraforming stuff, from the 1995 textbook (and presumably from popular sf long before then). I sure hope the world is not, as you suggest, a tide-locked satellite! (Oh wait--you didn't say "satellite of a super jovian world," which is what people always say when they are speculating along these lines, hoping for a world like Titan, terraformed into something more comfortable.) Science seems to work against such notions. If world is orbiting a jovian, then it is also bathed in steady radiation from Van Allen belts. If orbiting a terrestrial world, and tide-locked, then its day is bound to be too long (i.e., Luna's "day" is 28 days long); Roche Limit dictates how close in it can come and not break up, yet the closer in, the larger the primary looms (Luna looks plenty big now). And, as you noted, it would seem impossible for a satellite to have "moons" of its own, so these must be reassigned to different orbits, meaning that for observers on the "TS" world they will not behave as "moons" but as "planets." (I've been doing a lot of research on "satellites of super jovians" scenarios in the past year or so, FWIW . . . they first became popular probably due to Rand Corporation study PLANETS FOR MAN in the 60s, but knowledge of our local jovians has increased much since then and put some rather titanic gashes into the whole concept . . . ) =mantis= ---