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Henry Spencer wrote:
In article , Craig Fink wrote: Just wondering how big the tides on Titan might be? Maybe they're huge? Yes and no. Your intuition is correct that Saturn will raise very large tidal bulges in Titan. *However*, Titan is tide-locked to Saturn, so those big bulges don't move around much -- the moon is basically just a little bit egg-shaped all the time. Titan's slightly elliptical orbit will cause the bulges to move around a little, and also to change height slightly as the distance from Saturn changes. So they aren't *quite* completely fixed, but fairly close to it. How about tides due to other moons? (I think Rhea or Dione would be the best candidates.) They wouldn't be anything like the size of our lunar tides, but maybe there'd be a measurable effect. -- Fin ) |
#12
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In message .com
"Alex Terrell" wrote: Anthony Frost wrote: In message Craig Fink wrote: Just wondering how big the tides on Titan might be? Maybe they're huge? Approximately 0.5 * sqrt(f*ckall) most likely. What happens if one, but not both, of f or ckall are negative? Well, by experimental observation one of them is. It makes the tides imaginary... Anthony |
#13
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In article ,
Fin Fahey wrote: Yes and no. Your intuition is correct that Saturn will raise very large tidal bulges in Titan. *However*, Titan is tide-locked to Saturn, so those big bulges don't move around much... How about tides due to other moons? (I think Rhea or Dione would be the best candidates.) They wouldn't be anything like the size of our lunar tides, but maybe there'd be a measurable effect. Alas, I fear not. The Saturnian system is a big place. The distance between Titan and Rhea is never *less* than about twice the distance from the Earth to the Moon. I haven't time right now to wade through the numerical details, but it looks to me like inter-moon tides are going to be quite insignificant. -- "Think outside the box -- the box isn't our friend." | Henry Spencer -- George Herbert | |
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JRS: In article , dated
Mon, 17 Jan 2005 15:42:52, seen in news:sci.space.policy, Craig Fink posted : Just wondering how big the tides on Titan might be? Maybe they're huge? Low gravity in conjunction with a really big moon called Saturn. After all motion is relative. ;-) Our Moon has an angular diameter, from Earth, of 0.01 and a specific gravity of about 3. Saturn has an angular diameter, from Titan, of 0.1 and a specific gravity of about 1. The tidal field will therefore be about 1000/3 = 300 times greater. I forget the value of Titan's surface gravity; but, being proportional to specific gravity and to radius, it should be about a third of ours; and the seas there will be a little less dense than seawater. The tidal response should therefore be around three orders of magnitude greater than ours here, if other things were equal. Unequal things include : Titan's seas look smaller - our continental shoreline tides are much grater than our mid-ocean ones (cf. tsunami). Titan keeps the same face towards Saturn, with some libration; Earth does not keep the same face towards the Moon. But the distance Titan- Saturn varies too. The Moon's relevant period is about a day; Titan's is 16 days. Titan seems, on the whole, likely to be flatter than Earth; and it is very likely that some of the flatter-than-average parts will be near mean sea level. Thus ISTM that tide, as measured by the distance of ebb and flow, will probably be small but not imperceptible. However, if the "sea" is actually lakes rather than ocean, variations of local "rainfall" may have more effect. -- © John Stockton, Surrey, UK. / © Web URL:http://www.merlyn.demon.co.uk/ - FAQish topics, acronyms, & links. Correct = 4-line sig. separator as above, a line precisely "-- " (SoRFC1036) Do not Mail News to me. Before a reply, quote with "" or " " (SoRFC1036) |
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On Mon, 17 Jan 2005 16:46:20 -0700
Hop David wrote: Some web sites say Titan's tide locked. If it's tidelocked, the tidal bulge will stay put. Yes, but it will vary in size and position if Titan has an eccentric orbit around Saturn. To get a large eccentricity there would have to be another large moon. So Titan must have a low (but non zero) eccentricity and a small (but non zero) variation in the tide forom Saturn. We know Titan has wind. There must be an energy input from somewhere. -- Michael Smith Network Applications www.netapps.com.au | +61 (0) 416 062 898 Web Hosting | Internet Services |
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JRS: In article , dated Wed, 19 Jan 2005
15:20:10, seen in news:sci.space.policy, Henry Spencer posted : The distance between Titan and Rhea is never *less* than about twice the distance from the Earth to the Moon. Contributory, but non-essential. I haven't time right now to wade through the numerical details, but it looks to me like inter-moon tides are going to be quite insignificant. Assuming no Saturnian moon is much denser than say 3 (if it was 10 or more I'd remember) : At closest to Titan, in Moore units, Saturn subtends 75100/760000 radians, say 0.1 Rhea subtends 1100/432000, say 0.0025 Hyperion subtends 200/160000, say 0.00125 Iapetus subtends 2000?/1440000, say 0.0015 and the rest are obviously smaller. Tidal force goes as cube of angular diameter times density; so Rhea's tide at Titan is of the order of 50 ppm of Saturn's. At closest to Hyperion, i M u, Saturn subtends 75100/920000 radians, say 0.08 Titan subtends 3500/160000, say 0.02 So the tidal force of Titan at Hyperion is about 5% of Jupiter's. -- © John Stockton, Surrey, UK. Turnpike v4.00 MIME. © Web URL:http://www.merlyn.demon.co.uk/ - FAQqish topics, acronyms & links; some Astro stuff via astro.htm, gravity0.htm ; quotings.htm, pascal.htm, etc. No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News. |
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#18
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Michael Smith wrote:
We know Titan has wind. There must be an energy input from somewhere. Sunlight. Paul |
#19
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Dr John Stockton wrote:
JRS: In article , dated Wed, 19 Jan 2005 15:20:10, seen in news:sci.space.policy, Henry Spencer posted : The distance between Titan and Rhea is never *less* than about twice the distance from the Earth to the Moon. Contributory, but non-essential. The effect of tides is proportional to: m1.r2^4/m2.d^3 where m1 = mass of inducing body m2 = mass of subject body r2 = radius of subject body d = distance between the bodies Plugging in the numbers for an assortment of solar system bodies, we get the table below. (Tidal effects are normalised to Moon-on-Earth = 1. When both bodies are moons of the same planet, the minimum distance is used.) Inducing Subject m1 m2 r2 d Tidal body body (kg) (kg) (m) (m) effect -------- -------- -------- -------- ------- -------- ------- Sun Earth 1.989e30 5.974e24 6.378e6 1.496e11 0.459 Moon Earth 7.349e22 5.974e24 6.378e6 3.844e8 1 Sun Moon 1.989e30 7.349e22 1.738e6 1.496e11 0.206 Earth Moon 5.974e24 7.349e22 1.738e6 3.844e8 36.4 Sun Mercury 1.989e30 3.302e23 2.440e6 5.791e10 3.07 Sun Venus 1.989e30 4.869e24 6.052e6 1.082e11 1.21 Sun Mars 1.989e30 6.419e23 3.397e6 2.279e11 0.0973 Sun Io 1.989e30 8.932e22 1.822e6 7.784e11 0.00145 Jupiter Io 1.899e27 8.932e22 1.822e6 4.216e8 8720 Europa Io 4.800e22 8.932e22 1.822e6 2.493e8 1.07 Ganymede Io 1.482e23 8.932e22 1.822e6 6.484e8 0.187 Callisto Io 1.076e23 8.932e22 1.822e6 1.461e9 0.0119 Sun Europa 1.989e30 4.800e22 1.561e6 7.784e11 0.00146 Jupiter Europa 1.899e27 4.800e22 1.561e6 6.709e8 2170 Io Europa 8.932e22 4.800e22 1.561e6 2.493e8 1.99 Ganymede Europa 1.482e23 4.800e22 1.561e6 3.991e8 0.805 Callisto Europa 1.076e23 4.800e22 1.561e6 1.212e9 0.0209 Sun Ganymede 1.989e30 1.482e23 2.631e6 7.784e11 0.00380 Jupiter Ganymede 1.899e27 1.482e23 2.631e6 1.070e9 1400 Io Ganymede 8.932e22 1.482e23 2.631e6 6.484e8 0.296 Europa Ganymede 4.800e22 1.482e23 2.631e6 3.991e8 0.681 Callisto Ganymede 1.076e23 1.482e23 2.631e6 8.130e8 0.181 Sun Callisto 1.989e30 1.076e23 2.410e6 7.784e11 0.00369 Jupiter Callisto 1.899e27 1.076e23 2.410e6 1.883e9 249 Io Callisto 8.932e22 1.076e23 2.410e6 1.461e9 0.0251 Europa Callisto 4.800e22 1.076e23 2.410e6 1.212e9 0.0236 Ganymede Callisto 1.482e23 1.076e23 2.410e6 8.130e8 0.241 Sun Titan 1.989e30 1.346e23 2.575e6 1.427e12 6.24e-4 Saturn Titan 5.685e26 1.346e23 2.575e6 1.222e9 284 Tethys Titan 6.27e20 1.346e23 2.575e6 9.273e8 7.17e-4 Dione Titan 1.10e21 1.346e23 2.575e6 8.446e8 0.00166 Rhea Titan 2.31e21 1.346e23 2.575e6 6.950e8 0.00627 Hyperion Titan 2e19 1.346e23 2.575e6 2.590e8 0.00105 Iapetus Titan 1.59e21 1.346e23 2.575e6 2.339e9 1.13e-4 Sun Triton 1.989e30 2.14e22 1.353e6 4.498e12 9.55e-6 Neptune Triton 1.024e26 2.14e22 1.353e6 3.548e8 1000 Proteus Triton 5e19 2.14e22 1.353e6 2.372e8 0.00164 Nereid Triton 3e19 2.14e22 1.353e6 5.158e9 9.55e-8 Sun Pluto 1.989e30 1.25e22 1.195e6 5.906e12 4.40e-6 Charon Pluto 1.62e21 1.25e22 1.195e6 1.960e8 0.0979 Sun Charon 1.989e30 1.62e21 5.93e5 5.906e12 2.06e-6 Pluto Charon 1.25e22 1.62e21 5.93e5 1.960e8 0.354 -- Ross Smith ......... ......... Auckland, New Zealand "If you can keep your head when all about you are losing theirs, then you probably haven't checked with your answering service." -- Capt. B. F. Pierce |
#20
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Dr John Stockton wrote: Tidal force goes as cube of angular diameter times density Sure sounds right. Thanks for that. I think most flexing of tide locked moons comes from eccentric orbits (higher tides at periapsis, lower at apoapsis) There is another source of flexing I've been wondering about. My image of a tidelocked moon is a watermelon being spun about Saturn: http://clowder.net/hop/tidemoon.jpg Under normal circumstances the long axis of the watermelon remains pointed toward Saturn. But a brush against the watermelon would cause its long axis to wobble some. I imagine it would be like a pendulum. If another moon's synodic period were resonant with the period of this "pendulum", the wobble could build with time. -- Hop David http://clowder.net/hop/index.html |
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