How badly would it mess with our concepts of “day” and “night”? Would we cycle twice as fast?
I assume you are aware that day and night are caused by the rotation of the earth, and have nothing to do with the moon(s).
Day and night on the earth are defined by solar illumination, not lunar illumination. The number of moons is irrelevant.
Note that the one moon we currently have is, for a portion of its cycle, dark during the night; during that time it’s the equivalent of no moons, and we get by just fine.
DUH! I screw up basic, what, 4th grade science?! :smack:
I was reading something earlier (sorry, don’t have a link atm) that claimed that the Earth DID have two moons for a time…both created in the same event (a Mars sized planet slammed into the Earth and the debris from it formed the moon/moons). Eventually the moons collided (at ‘low’ speed) and coalesced into the moon we have today. Supposedly, evidence for this is that the side of the moon that points towards the Earth is significantly differentiated from the side that faces away.
-XT
Werewolf outbreak.
…
Impossible to say unless you specify the size and orbit of your second moon. A second moon of the same size as the existing one would only be stable in a resonant orbit.
Yes, on one of these.
More seriously, depending on the mass and distance of these moons, it might mess up the tides pretty bad, and that might have some fairly major effects on marine ecology.
What I wouldn’t give to see that on YouTube…
The now defunct second moon (if it did exist) was very small and would’ve been like a pea shooter into the moon. You would be bored looking at the ten-minute video: http://www.postandcourier.com/news/2011/aug/04/earth-once-may-have-had-2-moons/
That depends on how close the view was. A camera planted on the surface, say, watching a hundred-mile-plus tall wall of rock coming over the horizon. Or something orbiting the Moon. In fact, the slowness that makes it less spectacular at a distance would make it more spectacular close up I think since everything is happening slow enough to see. And while the second moon was very small compared to Luna, it was pretty big on a human scale.
600 miles is no pea. If the theory is correct, it would have been a cataclysmic impact. Yes, it would have taken a few minutes to complete, but I think the arcs of molten rock would have kept people entertained.
According to the article, the rock would not get hot enough to melt. That surprised me too–most collisions of this type have enough energy to vaporize rock, not just melt it, and my intuition is that an event like this could easily outshine the sun for a few moments. But they claim 5,000 mph, which is indeed pretty slow for space.
Still, I think the arcs of non-melted rock would look pretty cool.
Anybody who would get bored watching two moons colliding has no soul.
I find that really surprising, but I guess they have done the maths. Without incandescent rock it probably wouldn’t be that spectacular. How disappointing, I demand higher speeds for our moon collisions.
Wait, how did you think it worked?
I just forgot that earth rotation causes day vs night. Only because I don’t consciously think about it often.
Let’s see:
v = 5,000 mph = 2235 m/s
KE = mv^2/2
KE/m = v^2/2 = = 2.5e6 J/kg = 2500 J/g
Specific heat of basalt (pretty close to moon rock) = 0.84 J/(g*K)
(2500 J/g) / (0.84 J/(g*K)) = 2976 K
So, almost a 3000 kelvin increase–more than the melting point of basalt. But this assumes all the kinetic energy goes into evenly distributed heat. Some of it might instead fly away and stay as KE. On the other hand, the material at the surface of the impact site is getting all the KE input initially, so it seems like it should get incredibly hot. On the other other hand, maybe that incandescence would be blocked by the rest of the material.
So I dunno. There’s enough energy for incandescence, but it’s not so overwhelming that it couldn’t “disappear” somewhere. Not like a big comet, where there is so much energy (in the neighborhood of 1000x of this situation, per unit mass) that it would be dazzling even if much of it was lost.
Two sizeable moons with greatly different orbital periods would make for some interesting calendars.
They’d also lead to magical gates opening, at various phases of each, that could be used for instantaneous travel around the Earth.
It would presumably have an effect on the tide.