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<blockquote data-quote="Dr. Harry" data-source="post: 663313" data-attributes="member: 5468">Why yes, I am a rocket scientist ...I haven't scanned to see what has been posted; please forgive me if someone else has answered this already.&nbsp; The radius of Mars is 3,394 km, or 1.95 times the radius of the Moon.&nbsp; Angular size decreases linearly, so your planet would have to be ~751,000 km away from the Earth. &nbsp; &nbsp;&nbsp; The period of the arrangement can be found using Kepler's Third Law, about 6.15 x 10^6 s, or about 71 days.&nbsp; &nbsp; &nbsp;&nbsp; Kepler's Third Law links the period and the separation between the object's so if you want the &quot;Mars-moon&quot; to have a 28 day cycle (The Moon's sidereal cycle is 27.3 days, the solar month 29.5 days), the then Mars-moon would be at a distance slightly greater (1.05x) the Moon's current distance, and would be about 1.86 times the size that Luna is in our sky.What determines the period of the tides is not (directly) the orbit of the Moon around the Earth, but the rotation of the Earth on its axis.&nbsp; On Earth, we have two tides every ~25 hours - twice a day adjusting for the movement of the Moon in the sky.&nbsp; The distance Mars-moon would have two tides a day (one tidal bulge on each side of the Earth) adjusted such that for eavery 71 days, there would be 70 tidal cycles.&nbsp; Every day, high tides would be about 20 minutes later.&nbsp; &nbsp;&nbsp; Simply having a larger mass wouldn't automatically make the tides greater, what is important is the difference in the other body's gravitational pull from one side of the Earth to the other.&nbsp; For the Moon, this is a difference of 6.4%, a tad larger than what it would be if Mars were there.&nbsp; Mars at the farther orbit would have tides about half as great (3.3% differential).&nbsp; &nbsp; &nbsp;&nbsp; Actually, you could do whatever the heck you wanted with the tides.&nbsp; The simple model on Earth can produce tides up to about ~1 m.&nbsp; The much larger tides in many places are due to the sloshing of the seas in their seabeds.&nbsp; A Ocean floor of the right shape, for the &quot;tide wave&quot; traveling around the Earth can produce MUCH greater tides if it is near resonance.&nbsp; (The same way a crystal wine glass can be oscillated into shaking itself a part when the sound waves of just the right note hit.&nbsp; The greatest tide differentials on Earth are, I believe, about 17 m.&nbsp; &nbsp;&nbsp; The phobos object is entirely negligible.&nbsp; &nbsp; Hope this was interesting.&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Harry Leckenby</blockquote>

[QUOTE="Dr. Harry, post: 663313, member: 5468"] [b]Why yes, I am a rocket scientist ...[/b] I haven't scanned to see what has been posted; please forgive me if someone else has answered this already. The radius of Mars is 3,394 km, or 1.95 times the radius of the Moon. Angular size decreases linearly, so your planet would have to be ~751,000 km away from the Earth. The period of the arrangement can be found using Kepler's Third Law, about 6.15 x 10^6 s, or about 71 days. Kepler's Third Law links the period and the separation between the object's so if you want the "Mars-moon" to have a 28 day cycle (The Moon's sidereal cycle is 27.3 days, the solar month 29.5 days), the then Mars-moon would be at a distance slightly greater (1.05x) the Moon's current distance, and would be about 1.86 times the size that Luna is in our sky. What determines the period of the tides is not (directly) the orbit of the Moon around the Earth, but the rotation of the Earth on its axis. On Earth, we have two tides every ~25 hours - twice a day adjusting for the movement of the Moon in the sky. The distance Mars-moon would have two tides a day (one tidal bulge on each side of the Earth) adjusted such that for eavery 71 days, there would be 70 tidal cycles. Every day, high tides would be about 20 minutes later. Simply having a larger mass wouldn't automatically make the tides greater, what is important is the difference in the other body's gravitational pull from one side of the Earth to the other. For the Moon, this is a difference of 6.4%, a tad larger than what it would be if Mars were there. Mars at the farther orbit would have tides about half as great (3.3% differential). Actually, you could do whatever the heck you wanted with the tides. The simple model on Earth can produce tides up to about ~1 m. The much larger tides in many places are due to the sloshing of the seas in their seabeds. A Ocean floor of the right shape, for the "tide wave" traveling around the Earth can produce MUCH greater tides if it is near resonance. (The same way a crystal wine glass can be oscillated into shaking itself a part when the sound waves of just the right note hit. The greatest tide differentials on Earth are, I believe, about 17 m. The phobos object is entirely negligible. Hope this was interesting. Harry Leckenby [/QUOTE]

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