
Post by elementalred on Nov 25, 2017 20:49:31 GMT
Since tides are caused by the moon, I was wondering what would happen if a planet has more than 1 moon?



Post by February Steam of Foushoo on Nov 26, 2017 5:20:05 GMT
Tide goes in; Tide goes out. You can't explain that. sorry, I had to do it. In all seriousness though. You'd probably just have two conflicting tides. Depending the attributes of these moons you may have tides that feed each other(higher amplitude waves), tides that cancel each other out(lower amplitude waves), just twice the amount of tides in a day. All else unaffected this should be all the big differences.



Post by blackink on Nov 26, 2017 7:00:21 GMT
I support February Steam of Foushoo, as he said, it all depends on the attributes of the moons, how big are they? Is there a significant size difference between them? Do they rotate around their planet at the same speed or one is faster than the other? Do they even rotate at the same angle like the rings of saturn or does one go from east to west and the other from north to south.



Post by Omicron on Nov 26, 2017 8:41:55 GMT
I think it will probably be something along the likes of interfering sound waves: (From: Wikipedia) Some images to explain it a bit better: or , with the waves being the tides.



Post by elementalred on Nov 26, 2017 17:43:01 GMT
Well let's say a planet as 3 moons, two small ones and one big. They are all tidally locked and have a circular orbit, the bigger moon orbiting the slowest and being the farthest. So what would happen to the tides?



Post by Omicron on Nov 27, 2017 13:00:14 GMT
Well let's say a planet as 3 moons, two small ones and one big. They are all tidally locked and have a circular orbit, the bigger moon orbiting the slowest and being the farthest. So what would happen to the tides? I don't think we have enough information to answer this question. For example, we know the bigger moon is further away, but how much? And how much bigger is he? For example, if it's four times as big as the others, but twice as far away, the moon's gravitational pull on the planet would be just a big as either of the smallest. Information I think we still need:  How big is the bigger moon?
 Are the smaller moons the same size?
 If so, how big are the smaller moons?
 If no, how big are each?
 What are the velocities of the moons?
 If they are at the same velocity, what are the periodic differences between the moons? (I.E. moon 1 and moon 2 are exactly opposite from eachother, Δλ would be 0,5, or if they are about 1/3 of the circumference between them, Δλ would be 1/3)
These questions can all be answered relatively to each other. (I.E. saying moon 1 is 2 times as fast as moon 2, and moon 3 1/3 as fast as moon 2)



Post by blackink on Nov 27, 2017 15:41:19 GMT
Omicron I may be wrong but by newton's law, if it is 2 times as big and 2 times as far away shouldn't the gravitic pull be half as strong? (Because you consider the square of distance). Apart from that i fully support your question. elementalred Goin back to the 3 moons suposition, if we assume that the 2 smaller moons have 1/81 part of the planet's mass (like earth's moon), they rotate around the planet at the same distance in the same axis at the same speed but on opposite ends then you would have the tides you have right now but more extreme (high tides are more high and low tides are extremely low), this is because when our moon produces a gravitic pull it also forms an antipodal reaction on the other side of the planet, which would only increase given two moons (this is a supposition based on the effect when the moon and the sun are on the same side of the earth, tides start acting like this). Also, the difference in tides would depend by region, equator would have normally higher tides than the poles, since we now have 2 moons, it's harder for the tidal movement to compensate through dissipation. As for how this bigger and farther away moon would affect this composition is hard to say, since it has half the gravitic pull as the other bodies it's effect are less, but it could increase the difference in high and low tides when it aligns with either moon and decrease that difference when is not aligned. So it would result in the third wave on the right image that Omicron posted. P.S: Is this system even stable? Moons aren's supposed to be this big after all, normally they have around 1/300 of the planet's mass.



Post by Omicron on Nov 27, 2017 15:54:03 GMT
Omicron I may be wrong but by newton's law, if it is 2 times as big and 2 times as far away shouldn't the gravitic pull be half as strong? (Because you consider the square of distance). Ah yes, I just realized: The formula I thought of was E _{g}=GmM/r, but that one was for energy The formula for gravitational pull is F _{g}=GmM/(r ^{2}), so... oops... Edited the earlier comment.



Post by elementalred on Dec 2, 2017 22:58:17 GMT
Wow this is much more complex than I thought I'll try to give as much detail as I can.
The smaller moons are not the same size: Moon 1 is 382km, Moon 2 is 325km. As for the big moon, its size is 1937km.
For the velocity, Moon 1 goes to 6.42 km/s , Moon 2 is 4.50 km/s and Moon 3 is 3.99 km/s. As for the distance
I'm not sure what you mean by "periodic differences". Do you mean orbital period or rotational period?



Post by Omicron on Dec 3, 2017 9:26:03 GMT
Wow this is much more complex than I thought I'll try to give as much detail as I can.
The smaller moons are not the same size: Moon 1 is 382km, Moon 2 is 325km. As for the big moon, its size is 1937km.
For the velocity, Moon 1 goes to 6.42 km/s , Moon 2 is 4.50 km/s and Moon 3 is 3.99 km/s. As for the distance
I'm not sure what you mean by "periodic differences". Do you mean orbital period or rotational period?
"Periodic difference" means how the difference in how far the 2 objects are in the circle. Taking the earlier example, , the first waves have a periodic difference of 0, while the second ones have one of 0,5. (It doesn't count for the third circle however, as they have a different velocity, so for your tides question this shouldn't be important) (Also, we still need the distance from the planet)



Post by elementalred on Dec 4, 2017 20:53:06 GMT
Wow this is much more complex than I thought I'll try to give as much detail as I can.
The smaller moons are not the same size: Moon 1 is 382km, Moon 2 is 325km. As for the big moon, its size is 1937km.
For the velocity, Moon 1 goes to 6.42 km/s , Moon 2 is 4.50 km/s and Moon 3 is 3.99 km/s. As for the distance
I'm not sure what you mean by "periodic differences". Do you mean orbital period or rotational period?
"Periodic difference" means how the difference in how far the 2 objects are in the circle. Taking the earlier example, , the first waves have a periodic difference of 0, while the second ones have one of 0,5. (It doesn't count for the third circle however, as they have a different velocity, so for your tides question this shouldn't be important) (Also, we still need the distance from the planet) Moon 1 is 22585 km away from the planet, Moon 2 is 35658 km away and Moon 3 is 59122 km away.



Post by Omicron on Dec 8, 2017 9:36:51 GMT
Welp, I finally had spare time to look up how I could calculate tidal force, and apparently tides have nothing to do with the location of the moon, and only happen because the moon does not have a circular orbit compared to the Earth... (I thought it had to do with the fact that if the moon would be on the other side of the Earth it would be low tide, while when the moon is exactly above the Earth it'd be high tide, but that's false) So, as the example planet's moons all have a circular orbit, the tides would look something like this:
Tidal I force I_________________ Time >

