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[G-Flex]

Also, can't agree on the gravity causing the Moon to remain facing the Earth. Last time I checked, Mercury isn't doing anything of the sort, and it should be subject to much more stress than the Moon is.

That's the kind of thing that mostly happens with satellites, I think.

See: http://en.wikipedia.org/wiki/Tidal_locking#Mechanism

Apparently it's pretty normal for the moons of planets to do that.

[Sean Mirrsen]

Hm. Oh, yeah, forgot about the "earth is not a solid" thing. It's more of a softball with goo inside. Then yes, internal friction would gradually dissipate the relative rotation speed. So... worst comes to worst, should we put boosters onto the Moon to speed it up?

I still don't think it can affect the orbital speed though. It would make sense with conservation of energy, but it would make just as much sense for it to simply transform into heat.

[G-Flex]

Huh.

On the other hand, apparently tidal forces CAN cause orbital decay sometimes too ( http://en.wikipedia.org/wiki/Orbital_decay#By_tidal_effects ).

At any rate, it stands to reason that if tidal forces wind up eventually getting the planet-moon pair in a state of mutual tidal lock, then obviously tidal energy wouldn't work anymore. And in that case, if the orbit isn't decaying in some fairly particular ways, then we wouldn't be able to get any energy from the orbital pattern at all.


[edit]

And I don't have a link at the moment, but apparently the Earth IS somehow pushing the Moon into a higher and higher orbit gradually.

Actually, wait, Wikipedia has info on that too: "As a result of the conservation of angular momentum, the slowing of Earth's rotation is accompanied by an increase of the mean Earth-Moon distance of about 3.8 m per century, or 3.8 cm per year"

[Sean Mirrsen]

I don't know how to do it in scientific terms, but I suppose in layman's terms it appears to essentially work like a waterwheel in space. Since the object is becoming elongated due to gravity, the "elongated" part of the object that's pointing "down" acts as an anchor as it moves away from the other object due to rotation. Gravity exerts a force upon this, and since the gravity's effect still has some lag as it has to overcome the object's internal friction, there is a tiny net effect that pushes the rotating object along. If the rotation is going along the object's orbital movement, this effect would likely lower the orbit and increase the speed. In the other case, speed would decrease and the orbit would be higher. I haven't looked into planetary dynamics, so feel free do disregard this explanation.

[Sordid]

Also, can't agree on the gravity causing the Moon to remain facing the Earth. Last time I checked, Mercury isn't doing anything of the sort

Check again: http://en.wikipedia.org/wiki/Mercury_(planet)#Spin.E2.80.93orbit_resonance

[Sean Mirrsen]

I already saw what it was doing in the Tidal Lock article. I don't have any definite thoughts on the matter, so I won't contest that.

[Sergius]

How about this for unlimited free energy: we can harness the rotational forces of Newton's and Einstein's buried corpses.

[andrea]

hehe. true.

[RAM]

Hows this for perpetual energy, we mine out the earth, and burn it for enough energy to reach another planet. Then we mine that out, and keep going until we have enough surplus energy to keep an otherwise self-sufficient colony going until a nearby solid mass become unstable enough to explode and then have the shrapnel settle down enough to be mined out...

[andrea]

and what do we do when there are no more planets?

[Zironic]

Wait, I got it! We build a small dyson sphere around our planet, then through extreme pressure, make it turn into a small sun. We fly around the galaxy, seeding life, only to go back and gather the results and consume the planet. The whole time we alter our genetics and become cybernetic, using the victim planet's tech as fuel for our own....

Oh wait thats prey...

[Micro102]

eventually the moon will fall out of orbit and then if it doesnt make the earth fall out of orbit it could hit anothe rplanter and send our solar system into chaos

[Sean Mirrsen]

...it could hit another planter and send our solar system into chaos

DF has taken its toll on this one's grammar. I'd prefer it to hit a soapmaker, personally.

[Sordid]

eventually the moon will fall out of orbit and then if it doesnt make the earth fall out of orbit it could hit anothe rplanter and send our solar system into chaos

Nah, not really. It's not nearly big enough to do any major damage to the structure of the solar system, nevermind that it's extremely unlikely it would actually hit another planet. More likely it'd just swing by, alter its orbit slightly, and be ejected from the system.

[Sean Mirrsen]

Not with Jupiter, the vacuum-cleaner of the solar system, around. If there's any likely place the Moon is going to end up after leaving Earth, it would be Jupiter, second only to the Sun.