Keep in mind that the answers given so far are true for a two body system. The system is unstable if there are three or more bodies (i.e. the sun, Jupiter…). There is a possibility that the moon will crash into the Earth.
Is the moon tied up in the earth's gravitational pull at the very least? Or do both pulls match at some point to circle the earth?
Submitted 1 hour ago by Patnou@lemmy.world to [deleted]
Comments
zwerg@feddit.org 1 hour ago
skibidi@lemmy.world 55 minutes ago
The moon is receding from the Earth and would eventually roughly double its orbital period, while Earth’s rotation would nearly stop (one rotation every 47 days), and both would be tidally locked to the other. The same side of the Earth would always face the moon, and the same side of the moon would always face the Earth (as happens currently).
This is all assuming the system would continue unperturbed forever, however, it won’t. Before the above happens, the sun will turn into a red giant and the drag from the expanded atmosphere will slow down the orbits of both the Earth and Moon, eventually leading to them both ceasing to exist - the moon from reaching the Roche limit above the Earth, and the the Earth from entering the Sun’s photosphere and eventually spiraling into the core.
T00l_shed@lemmy.world 1 hour ago
You are correct that they orbit a mutual point, which is not the earth’s core, but actually outside of it, which is known as a barycenter
Patnou@lemmy.world 1 hour ago
Not looking to fight just trying to understand. If that is true at a certain point then there is a position which both pulls are the greatest? And if something big enough or small enough passed through said point would it not feel the pull on both sides or get ripped apart if the object was weak enough?
Legianus@programming.dev 1 hour ago
Astrophysicist here, I think you’d enjoy reading about the Hill Sphere and Roche limit. Not quite what you are asking for but comes close.
trxxruraxvr@lemmy.world 54 minutes ago
The barycenter of the earth and moon is outside Earth’s core, but still inside earth. On average (since it changes with mountains and such) about 1707 km deep. So technically earth itself is contently paint trough that point without being ripped appart. The forces are strong enough to move water on earth’s surface though, this is what causes tides in the seas.
Assassassin@lemmy.dbzer0.com 1 hour ago
That’s not really how gravity works. As you move closer to one object, the balance of gravitational forces will shift. If you move away from the earth and toward the moon, you’re going to eventually be pulled equally by both, leading to zero acceleration toward either.
In order for something to be pulled apart by two different gravitational forces, you’d need to be able to have a massive change in gravity over the distance of that object. For something planetary sized, this might be possible, but for anything on the scale of a human, you’d need something like a black hole event horizon to get enough of a force gradient to do damage.
Gravity is actually a pretty weak force compared to almost all other basic forces, and it doesn’t often get “concentrated” like other forces can.
If the moon-earth gravitational system was able to generate enough force to rip something apart at some specific point, space travel would certainly be a lot more interesting/daunting.
ShellMonkey@piefed.socdojo.com 1 hour ago
Not a physics major here, but that would have to be exceptionally weak to be pulled apart as I see it. Even on the surface of earth you can hold a piece of tissue paper up and effectively neutralize the force of gravity without it pulling itself apart.
The bonds holding the molecules together would have to be weaker than the force of gravity pulling them apart, which would essentially make it into a gas I suppose.