I was pondering the other day when I was supposed to be paying attention in econ. If we somehow came up with the material to make a 240,000 mile (distance from moon to earth rounded up for extra length) long rope, and anchored it to the moon with the untied end hanging to earth, how would it act? If the description doesn't make sense, here's a little picture I made (no art promised):



I've always thought of what it'd be like to see "the moon rope" just floating by, and I'd wonder what would happen if you grabbed on to it, and hung on to see where it would take you. Since the moon always faces the earth with the same side, it wouldn't wrap around or anything.

I've only taken one year in physics, and I haven't really researched how an object in two different gravities would react. If this would work, and the rope drug around on Earth, that would be something incredible to see.

I think it would snap under its own weight.

Post has been edited 1 time(s), last time on Nov 22 2007, 4:58 am by Doodan.

There is one guy trying to make a space elevator using carbon fiber, which is the only material strong enough and flexible enough to expand all the way out to space from Earth. If this elevator project succeeds, they may stretch it to reach the moon one day, but that'll take an extremely long time and lots of carbon fiber to synthesize.

Spider silk ;D maybe we can have restraunts and stuff on the rope too, with some lookout points.

True.

However, if we assume

(a) the mass of the rope is negligible, and therefore
(b) the rope will not break, and we also assume
(c) any velocity induced on the rope by the moving moon does not cause significant friction with Earth's atmosphere

then the rope would indeed trail around on Earth's surface. Since Earth is by far the larger mass, a larger portion of the rope would be in a part of space where the gravitational pull of the Earth is greater than that of the Moon. Assuming a rope of negligible mass, the rope would just trail around on Earth, and, yes, it would be a sight to behold. The practical problems with this, assuming such a rope could be assembled and securely anchored to the Moon against infinite force, are

(a) as Doodan said, the rope would break from its own weight unless its total mass is relative quite small or it has immense tensile strength
(b) the velocity of the Moon relative to the upper atmosphere is probably great enough to cause that part of the rope to melt
(c) IF the rope was heavy and did not break (and it never snaps its base at the Moon), it could drag the Moon out of orbit, with catastrophic results on Earth

Interesting hypothetical question though.

The friction with the air would probably make it bounce/pull out of the atmosphere, unless it was anchored to something heavy, which would cause other problems.

If we had enough force to pull the moon towards the Earth, we'd eventually hit the Roche limit, causing the moon to form into a ring. That'd be sweet, but as DTBK said, no moon = bad.

I'm assuming that the earth and the moon both rotate (ie, the same point on the moon isn't always facing the same point on the earth)... which would cause the rope will to stretch and break.

Actually, the same point on the Moon is always facing the same point on the Earth. That's why we talk about the 'dark side' of the Moon, i.e. the side of the Moon that will never be visible to Earth. (Yes, the Earth and Moon both rotate, but in synchronization that keeps one side of the Moon always facing us.

Also note that in his dream, the rope is not attached to Earth, it is left to float freely.

Aha!!! A new power source!!

Two carts.


=
====
========
==MOON==
========
=====
_O_O_
=Cart=
=====
|
|
|
|
ROPE
|
|
|
|
=====
=CART=
--O--O--
=========
EARTH ===



The cart transforms the wheel turning energy to electricity by using superconductivity (this way the generator can be tiny)

The first person to say "OMG but then the carts won't be moving very fast so lol it won\t make mucch emeegy11!" gets slapped.

The rope is made of Carbon nanotube, and the cart "moves" over rails going through Russia, Canada, Norway, Finland, Greenland, etc. There are boats waiting to ferry it across the few miles of sea.

NOTE: The cart really is quite a bit smaller than on the diagram.

Post has been edited 1 time(s), last time on Nov 25 2007, 10:41 am by Viii_iiiV.

By the Law of Conservation of Energy, this would inevitably sap the Moon of its kinetic energy (velocity) through friction and therefore the Moon would eventually fall to Earth.

I'd be dead by then though, AND, if we managed to do this, then we could work out how much friction to add to make sure the moon lands on China.

EDIT: And DTBK, if you want me to remove my sig, just PM me.

You do realize the moon landing on china would kill the ENTIRE human race, right?

The moon landing virtually anywhere would kill the entire human race...

Remove the 'virtual' and there you have it, and we can throw in everything else that lives.

However, I doubt there would be enough velocity in the Moon's descent to let it actually hit - it would be broken apart by the much-larger Earth's gravity well long before it was truly dangerous on that scale.

Doh! Maybe if it landed in the Himalayas? That's quite far from the sea.

Hey, wait a second.. But if you think about, because the path of the orbit would be spiralling inwards until it was obstructed by the earth, it would make a big smear of moon dust - so it wouldn't kill that much.


And anyways, if it slowed it down then to keep in orbit the moon would have to go further away... not too good for my rope, but a bit better for keeping humanity alive.

That wouldn't matter. The earth, speeding at tens of thousands of MPH, would be decelerated by either hundreds or thousands of MPH, basically sending everything towards the opposite direction of the impact, most likely killing everyone. Newton's first law comes into thought.

ugh.. How could a boat ferry a cart attached to a rail. It would make more sense to bridge the water anyway rather than spending energy you're trying to gain on powering boats.

Microscopic fibers of an infinitely lightweight and durable material woven together. There has to be an element we could use for this, with a high melting point as well. I think we can expect destruction wherever this rope goes .

Lmao at the moon-rope. Assuming this was successful, what would you use it for? Just swinging around? What would happen if you got a space suit (couldn't think of a more eloquent term) and climbed the rope to the moon? Sorry if the answer is really obvious, I really know nothing of this stuff.