Let’s say you get an extremely long, infinitely strong cable (made of unobtanium) and anchor one end to a point on the earth (let’s say not at one of the poles) and anchor the opposite end to the moon. The cable is very taut. What would happen? Would the orbits get completely out of whack? And what kind of tension would that cable feel?
As the result of rotation, the moon would slowly wind itself around the unobtanium cable until it pulled itself into the earth–reunited after several billion years!
The ends would rip out and cause destruction as the now loose cable comes crashing onto the earth. Being infinitely strong it should be able to cut through a lot of the earth.
One or the other of the cable ends would pull free from its mooring.
I believe the Moon is slowly circling away from the Earth (wiki says 3.8 cm/year).
The cable will eventually snap (unless it was unbreakable), or one of the anchor points pulling free. This should result in the cable “whipping” either the Moon, or the Earth, or both. Wear a hardhat.
If the cable was unbreakable (as well as the moorings), it’s my wild-ass-guess that there might be a “rebound” effect, causing the moon to reverse direction, and slowly approach the Earth. The speed would depend on how “elastic” the cable was.
I think what we all can take away from this is that we should not try this experiment at home!
However, I forgot another thing.
The Moon does not remain over the same point on the Earth. (The Earth rotates once a day, the moon completes an orbit once every 27.3 days.)
The cable would then start wrapping around the Earth, as the Earth-side anchor “reels in” the Moon (assuming unbreakable cable), like a fishing rod. Whata whale of a fishing story…
Also, consider that the Moon orbits on Earth’s ecliptic plane, not her equatorial plane. (The earth is tilted.)
Depends on where the rope is anchored. If you have a pivoting anchor at the right place, the rope just follows the moon around.
Yup. This is actually a fascinating question. There’s a lot going on there. The moon always presents the same face (more or less) to the Earth, so it revolves maybe once every 27 days or so. The Earth, on the other hand, makes a full revolution every 24 hours. With a circumference of roughly 24,000 miles, and assuming that the cable doesn’t cut the Earth in half like a Duncan Yo Yo, it will reel the moon in within 10 days or so. All that orbital energy has to go somewhere, so, I think, the moon is going to be whipping very fast at the end there. (The cable will be glowing in the ultraviolet as well, if not emitting gamma radiation.)
All told, it’s gonna be a bad coupe of weeks to be an Earth dweller.
Is your anchor point somewhere on the globe where the moon is always visible in the sky? Where is that?
For some reason, I had only considered the anchor point closer to the equator…
I’m just picturing a ball (not the earth, so maybe I’m all wet here), with another ball orbitting ecliptically. If an anchor were at the poll, it seems to me that a cable could follow, perhaps scraping the earth, but not wrapping it. Am I nuts? (This is a very real question - my grasp of astronmy is, er, questionable)
I imagine one of the pole would do, with the land available at the South Pole making it the best choice.
The earth is tilted 23 degres, or so, right? Is the Moon always visible form the North or South Pole?
With unbreakable cable anchored on one of the poles, and a slightly titled earth:
Would the Moon “yank” the Earth more “off kilter”?
Would the Earth yank the Moon into a more erratic orbit?
(I’m thinking both…)
I missed the edit window earlier… Yes, the cable would slowly scrap along the ice during part of the month, killing many penguins.
The Earth and Moon are already connected by the cable that is gravity. The drifting away of the moon would be the only change in the dynamics. If attached at the pole it might pull the Earth more upright.
Or giving them quite the jump rope competition opportunity.
Think of it as a new evolutionary opportunity!
Are you sure? Hmmm. I’m trying to visualise this…
The Earth and the Moon both orbit a common center of gravity. (This center of gravity may lie within the perimeter of the Earth’s crust, I am not sure.)
The Earth, in it’s orbit around the sun, “wobbles” further away and then back in closer again (from the Sun’s perspective), due to the Moon’s pull on Earth.
My gut tells me more would change in our orbital dynamics than just halting the Moon’s outward drift, if we set in a rigid cable into the equation.
In space, if I nudge an orbiting body, that body will react in a relatively simple newtonian manner. Add a cable linking me to the object, I affect both of us, depending on the tension/elasticity characteristics of the cable, and the ballistics path we take is changed in a different way than without that cable.
Throw a set of Bola, and they snap outwards, circling around a common center. (Since the balls of a bola are the same size as the other, the center is midway down the connecting cable.) The “Earth-Moon bola”, as it is now, is using only a “connecting chain” of gravity. But this chain is pretty elastic, even if high efficiency and low drag…
Of all the above posts, this is the only one that accurately describes what would happen . . . up to a point. Yes, the moon would whip around the earth, trying to catch up to the earth’s rotation. And yes, the earth would reel in the moon, with the tether wrapping around the earth (though the danger of it slicing through the earth is very real). And yes, the moon would be whipping around very fast at the end . . . fast enough that both bodies would crash into each other and break up spectacularly . . . eventually re-forming into something like its original planetary mass, possibly in a different orbit around the sun. No survivors.
By the way, some of you are thinking that the cable would simply replace the earth/moon gravity, since both bodies revolve around a common center of gravity. But that center of gravity is always moving, since the earth rotates much faster than the moon revolves. If that weren’t the case, if the center of gravity were fixed, like the end of the cable, there would be a location on the earth from which the moon would always be directly overhead. And that location would always be a high tide.
I’ve thought about it some more.
By attaching a cable from the earth to the Moon, you have effectively changed two orbiting bodies into a single (unevenly balanced) unit.
Not only would such a cable (attached at one of the Poles) not “pull the Earth upright”, it would have the opposite effect: the Earth’s rotational axis would pe pulled towards the Moon (and the Moon would be pulled out of its ecliptic orbit into something more radical).
Earth’s “wobble” and tilt would become more and more pronounced, until the pole (and the Earth) eventually point directly at the Moon (in the Moon’s new orbit, which would be slowed dramatically, as well, due to having to drag the Earth into it’s new position), and this new rotation would match whatever the new orbital period of the Moon became.
The Earth’s “old” axial rotation would remain, making for a situation where the sun would appear to rise in a new direction each “day”.
If the anchor was in the North Pole, the North Pole would be dragged into pointing at the Moon all the time. So the Sun would appear to adopt a north-south “drift” across sky some days, south-north others. (Assuming that the Earth/Moon bola is spinning counterclockwise along it’s path around the sun, the time the old North Pole is moving away from the sun, the sun appears to have a southward drift. When the old North Pole begins to move towards the sun (as it follows the Moon), it will appear that the sun is drifting northward.)
With the old axial rotation still going on, this would make the sun seem to move from North east to southwest at one extreme, with the dawn sun rising further south each “day”, until the sun rises in the south east, and moves north west, and then the cycle reverses itself.
I think. It’s tough visualising this three dimentional spinning balls stuff.
Basically, our day is determined by one simple west to east spin (Counter clockwise, when seen from above the North Pole). But now we have to add in a much greater tilt (not 90 degrees, but pretty drastic, nonetheless), and a new additional spin, that the Moon imparted to the Earth.
If the Moons orbital speed slows, won’t it then no longer be able to keep itself aloft? If so, then the gravitational attraction to each other causes the Earth and Moon to come together. Probably none too gently.
Please consider why I felt that being tied together by a cable is not the same as being tied together solely by gravity:
Planet-killer asteroid mlees2008a is on an intercept course with the Earth/Moon system. This asteroid hits the Moon. The Moon is nudged away from, or into, the Earth, depending on the direction the asteroid came from, and it’s mass. With gravity being the only thing holding the Moon to the earth, the Earth remains unaffected until the Moon hits the Earth, or moves far enough away that the tidal forces fade away. (Hmmm. Earth’s orbit would probably change into something a little bit more erratic if the Moon spun off into space, a-la-Space 1999, on it’s own through, such a collision. Uh-oh.)
Planet-killer asteroid mlees2008a is on an intercept course with the Earth/Moon system, and that system is tied together with an unbreakable cable. The asteroid hits the Moon. The Earth feels the effect relatively quickly (depending on the exact characteristics of the cable material). Both Earth and Moon twirl like a set of unbalanced bolas into a new path around the sun.
(I hope I am on the right track here. I am just a high school grad… please be gentle.)