Only if you put those tidal generators on the Moon.
The rotation of the Moon does not really affect the tides on Earth. Tides on Earth are largely the result of the difference in pull of gravity on the side nearest the Moon versus the side of Earth farthest from the Moon. There’s a similar smaller effect for the Sun. The two cycles are out of phase with each other, which contributes to Earth’s ocean tides being an oscillating cycle. Not the high tide vs low tide, but the high high tide versus low high tide, i.e. spring tide vs neap tide.
To some small degree, the not quite even lunar density would mean the center of gravity would oscillate closer and farther from Earth, which would make a small change to the tidal pulls. But that is small compared to the other factors that affect ocean tides, including the ocean floor and coastal shapes.
There would also be some slight lessening of the tides over time as the Moon moved farther away from Earth over time. This is because the Earth’s tides would create a torque on the Moon, robbing it of angular momentum, which then means it goes slower, so it orbits farther away.
IMO the lopsided nature of the Moon has almost nothing to do with it.
Any situation with a central rotating body and a rotating satellite will experience tidal forces on each body. This will tend first to tidally lock the smaller such that one side of it always faces the larger. In our case, the lumpy nature of the Moon determined *which *side ended up facing Earth, but not that *some *side would do so.
Once the smaller is tidally locked the next step will be slowing the large one’s rotation towards the period of the smaller one’s orbit. Such that eventually the larger’s “day” is the same as the smaller’s orbital period and the smaller continuously hovers over a single spot on the larger. IOW, they’d end up in the same relationship as an artificial geosynchronous satellite has to Earth today.
There’s an interesting dance here that some of this energy goes into heating the bodies, and some goes into expanding the orbit of the smaller body.
So while Earth will eventually have a “day” that’s 30+ now-days long, the Moon will have spiraled out some distance at the same time.
Obviously this process takes a very long time. Longer in fact than the larger situation will remain stable. The Sun will incinerate the Earth long before the Moon’s tidal forcing has enough time to tidally lock the Earth to it. But that’s just what the Moon is doing now: tidally locking Earth to itself.
Is the moon locked onto Earth because there is more mass on that side, or is there more mass on that side because it’s the side locked onto Earth? (As in, the Earth’s gravitational influence “pulled” matter that way.)
To LSLGuy’s post, I’ll just add that it’s not really a matter of “the next step”: Both steps occur at the same time; one just finishes quicker than the other.
Yes to both. Being near to Earth causes a distortion, the distortion causes the rotation to slow to match the revolution, and the closer the rotation matches to the revolution, the larger the distortion can become.
It’s clearer if you look at an object that isn’t yet completely locked, like the Earth to the Moon: The solid matter of the Earth wants to assume the same lopsided shape that the oceans do, but it doesn’t, because rock doesn’t flow nearly as easily as water. It would take considerably longer than a month for rock to flow that far, and in that time, the pull is turned around every which way, so the rock-flow never catches up. But it is still distorting a little, which is heating up the Earth and slowing it.
How about building a train track circling the equator. We could add more and more solar-powered engines to the track, going as fast as we can make them go. When that track is packed full of engines circling the globe, we’ll build more parallel tracks and fill those with engines too. When the moon is finally spinning at the desired rate we’ll set off charges under the tracks and blow all the engines to smithereens and into space.
There is no reason to “blow all the engines to smithereens…into space”; you can just keep running the trains and adding mass to balance the momentum transfer until you get the desired rotation. Of course, they trains are going to have to be going ridiculously fast and/or extremely massive, and they can never stop. Where the energy is going to come from this is another question entirely. This is literally orders of magnitude beyond the amount of energy produced by all human action in history.
That was basically my gyroscope idea, but since the moon has some stability to recenter itself we can use that to rock the moon back and forth using such a method which negates the reason for having to maintain the powered rotating system or the alternative, send them into space.
To concept of just exploding them won’t work unless the components leave the moon’s gravitational field, The same with rockets, the exhaust must leave the moon’s gravitational influence, and the effect you get from them will ultimately be from the speed of the exhaust gasses as they leave the influence of gravity, not the exiting the rocket nozzle.
Wondering if it’s easier to change the orbit of the moon instead of it’s rotation. If we make it closer (or further) to earth and the rotation remains the same it will then be rotating as we view it.
I assumed you are being facetious, but if we could capture the complete output of the Sun for 10 seconds our energy problems for the foreseeable future would be reduced to transmission infrastructure, i.e. how to transmit it to Earth and convert the collected energy for use in transportation and other off-grid applications.
I think we’re both saying the same thing from different ends of the telescope.
As you say, on a human scale the energy required to spin up the Moon is astronomical. Meanwhile, as I say, on an astronomical scale the energy is relatively trivial. In either case we agree that the engineering to harness the requisite energy and couple it to a nearby handy lump of rock is pure SF.
Ref you last point, I also suspect that if we did have a magic conduit to funnel the Sun’s total output to Earth, even briefly, we’d simply incinerate the planet. The total energy input would be roughly 2E9 times what we’re used to. I’d hope that even Oklahoma Republicans would agree that this would be A) undeniably AGW, and B) undeniably bad. But I’m not holding my breath on this last point.
Clearly, this is an hypothesis and one that I presume has a good bit of support. But I’ve often wondered if another explanation for the difference in density is that the earth over the years has protected the side of the moon that faces us from meteoric impacts. While that would seem to argue for greater density on the* far *side, it seems as if it is has potential to create a different type of surface from one side to the other. And maybe that difference is manifests in different density. Just wondering.
The Earth does almost nothing to protect the facing side of the Moon from impacts. The reason that there is a more even distribution of craters on the far side is that most of the impact craters date from very early in the Earth-Luna evoluton, and on the near side significant tectonic activity resulting from tidal forces between the Earth and Moon resulted in large magma flows (maria) that cover much of the Earth-facing side of the moon, including the massive Oceanus Procellarum, Mare Figoris, and Mare Imbrium. (Apologies if I missed on the spelling; don’t have time or bandwidth to look them up.) These maria have covered the older impact craters, and even those that exist within maria are less visible because of the low albedo of the regolith in those areas. The younger craters like Tycho are also very prominent, and we can see there are relatively few of those since the formation of the maria and the cessation of lunar tectonics around 3 BYA.
Although the impact craters look dramatic they’re relatively shallow and don’t contribute much to the Moon’s mass distribution, the bulk of which is dominated by the solid upper mantle. The reason the Moon as more mass on the Earth facing side is because while the Moon was still tectonically active the Earth pulled outward on the then liquid mantle, damping the rotation and creating a bulge. To address the earlier question by Atamasama, both speculations are true; the mass offset is due to Earth’s influence on slowing and locking the Moon’s rotation, and the Moon’s tidal locking is due to that offset. That tidal locking, by the way, happened very early in the formation of the system; probably within the first 20 million years and almost certainly within 50 million years.
This has proven to be very useful because it gives a differentiation between an almost tectonically inert surface on the far side and some more ‘recent’ activity on the near side, which allows us to estimate the frequency and size of meteorite impacts over time based on both crater size and count and on near-surface mass concentrations mapped by the Lunar Orbiter program. If we do send another sample return mission to the Moon (crewed or robotic) it should be directed to a far side site where we don’t currently have any samples to inspect, which may tell us much about differing composition of meteorites.
