astrophysics question

Post #322,214 by rcareaga 3/1/10 11:02:28 PM Reply	astrophysics question Anybody here feel competent to answer this? Planet (or rather satellite) Pandora orbits a gas giant. Wouldn't it be tidally locked to its parent rather than turning on its axis at something like a 24-hour cycle? cordially,
Post #322,215 by Another Scott 3/1/10 11:34:16 PM Reply	I haven't seen the movie yet. But the Sun is supposed to turn into a Red Giant as it burns up its hydrogen. Such stars are not very dense in their outer layers. I dunno how the rotation would be affected. But it's not a pretty future. http://en.wikipedia....un_as_a_red_giant More on "tidal locking" here - http://en.wikipedia....iki/Tidal_locking HTH. Cheers, Scott.
Post #322,216 by malraux 3/1/10 11:47:44 PM Reply	Hush, you. Yes, most sizable moons in our solar system are tidally locked (Pluto and Charon are tidally locked to each other, in fact). Mimas orbits Saturn in a bit under a day, so that's probably the mechanism used, not rotation. Alternatively, consider the possibility that unobtanium has the effect of somehow (waves hands wildly) nullifying the tidal bulge needed to do the locking. Or something. But if the moon is both rotating and orbiting, once every orbital period you'll have a very long night. Dude. Floating mountains, 12-foot tall naked blue women. Who's paying attention to the damned plausibility at this point, anyway? Regards, -scott Welcome to Rivendell, Mr. Anderson.
Post #322,217 by mvitale 3/1/10 11:56:23 PM Reply	Worst part of the movie: Unobtanium? Really? Their budget was HOW MUCH, and they couldn't come up with a better name than UNOBTANIUM? Fail. -Mike "They that can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety." - Benjamin Franklin, 1759 Historical Review of Pennsylvania
Post #322,218 by malraux 3/1/10 11:57:08 PM Reply	I like the name. It's self-deprecating, and such. Regards, -scott Welcome to Rivendell, Mr. Anderson.
Post #322,220 by static 3/2/10 5:28:00 AM Reply	I agree. It's like they're having a quiet laugh with the science wonks in the audience. :-) Wade. Q:Is it proper to eat cheeseburgers with your fingers? A:No, the fingers should be eaten separately.
Post #322,251 by SpiceWare 3/2/10 4:51:13 PM Reply	it's actually appropriate http://en.wikipedia.org/wiki/Unobtainium Since the late 1950s, aerospace engineers have used the term unobtainium when referring to unusual or costly materials, or when theoretically considering a material perfect for their needs in all respects, except that it does not exist. By the 1990s, the term was in wide use, even in formal engineering papers such as "Towards unobtainium [new composite materials for space applications]". The word unobtainium may well have been coined in the aerospace industry to refer to materials capable of withstanding the extreme temperatures expected in reentry. Aerospace engineers are frequently tempted to design aircraft which require parts with strength or resilience beyond that of currently available materials. http://md1.csa.com/p...480&setcookie=yes
Post #322,221 by static 3/2/10 5:33:25 AM Reply	Not necessarily. I wasn't looking carefully enough at the sky shots that showed the host planet to ascertain their relative positions, but it could be doing something bizarre like revoling within a polar orbit. Heck, Uranus in our own system has a tilt of over 90 degrees, so wierdness is definitely possible. Wade. Q:Is it proper to eat cheeseburgers with your fingers? A:No, the fingers should be eaten separately.
Post #322,224 by boxley 3/2/10 10:50:53 AM Reply	reply from an astrophysicist Don't know why the type of star would have any effect. The only evidence is from the Solar System, where none of the rocky planets are locked. The Moon is locked because it's lumpy (not a uniform sphere). Locking occurs also when the bodies are relatively close in mass and close together compared to their radii. Not the case with stars and planets. Funny, I would be more concerned about blue skin - or being manipulated by James Cameron again (I bolted on "Titanic", too much for me). from drl If we torture the data long enough, it will confess. (Ronald Coase, Nobel Prize for Economic Sciences, 1991)
Post #322,225 by malraux 3/2/10 11:18:59 AM Reply	Does he know it's a moon? Just about every moon in the solar system, large or small, is lumpy enough to get locked. Titan is larger than Mercury and it's locked, and that's around Saturn. Regards, -scott Welcome to Rivendell, Mr. Anderson.
Post #322,226 by boxley 3/2/10 11:22:40 AM Reply	prolly not, the blue people live on a moon? If we torture the data long enough, it will confess. (Ronald Coase, Nobel Prize for Economic Sciences, 1991)
Post #322,258 by malraux 3/2/10 8:39:15 PM Reply	Orbits a gas giant, yes. Regards, -scott Welcome to Rivendell, Mr. Anderson.
Post #322,257 by static 3/2/10 8:23:30 PM Reply	Blue skin. My knowledge is sketchy but the skin colour would be an artefact of the colour of the atmosphere, much like how plants on Earth are green - this enables them to take most advantage of red and yellow light. I don't know how this works for fauna, though. However, James Cameron is on record as having selected blue skin for his Na'vi for purely artistic reasons. :-) Wade. Q:Is it proper to eat cheeseburgers with your fingers? A:No, the fingers should be eaten separately.

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