You are only browsing one thread in the discussion! All comments are available on the post page.

Return

hperrin ,

I mean, no, not really. The gravitational center of the sun-earth system is within the sun itself, so the earth definitely orbits the sun and the sun definitely does not orbit the earth. Let alone the fact that the sun’s movement is predominantly driven by Jupiter. (The gravitational center of the sun-Jupiter system is just above the sun’s surface.)

gapbetweenus ,

Pretty sure you can chose earth as fix point and have everything rotate around it on really strange orbits. Everything is kind of relative.

Ashelyn ,

Wouldn’t that break relativity tho if you treat the earth as a fixed point? Stuff really far out would have to be going absurdly faster than light to orbit the earth once every 24h. I feel like that’s one of the ways to tell whether or not you’re rotating, or stuff is orbiting you.

gapbetweenus ,

Why would objects far out need to orbit earth every 24h?

Wouldn’t that break relativity tho if you treat the earth as a fixed point?

To be honest, physics was never my strong point. If I remember correctly you could chose any point as your observational (?) point but maybe someone with some real physics cred can chime in.

paholg ,

If the earth is fixed (not just in position, but in rotation), you’re using a non-inertial reference frame, and things get wonky. But you can make the math work.

Natanael ,

Relativity works when earth is the center because it’s relative, we just calculate everything with earth as the frame of reference. It does make a lot of math harder, but that’s what we already are doing when using earth based telescopes (although we try to shift the math to a more reasonable frame of reference for most stuff, but earth is always the starting point because we’re making all the measurements from here)

douglasg14b ,
@douglasg14b@lemmy.world avatar

Except that any two gravitational bodies orbit a common center…

The Earth orbiting the Sun causes the sun to wobble slightly, moving its orbital center away from its center of mass, which means the sun and earth actually orbit a common center point no?

Even if that center point is within the other body it still isn’t the center of that body, therefore they both orbit a shared gravitational center that is not the center of either body.

hperrin ,

I would not call it orbiting if the center is within the body. So, since the center of the sun-Jupiter system is just outside the surface of the sun, I would say the sun and Jupiter orbit the center of their system, but since the center of the sun-earth system is within the body of the sun, I would not say the sun orbits the center of this system. The path the sun takes in this system is entirely contained within its body.

Now, since the sun, Jupiter, and earth are all in the same system, there’s even less reason to say the sun orbits the earth, since the earth has a negligible effect on the sun’s motion.

douglasg14b ,
@douglasg14b@lemmy.world avatar

Just because you believe that a negligible effect means that it shouldn’t be called orbiting doesn’t change the fact of the matter that there is still a shared gravitational center that both bodies orbit around…

It doesn’t matter if it’s negligible or not, the fact of the matter is that such a point exists and both bodies orbit around that point.

hperrin , (edited )

Then literally everything is orbiting literally everything else, and the word orbit is completely useless.

I have a gravitational effect on the earth. The earth-hperrin system has a gravitational center that both bodies revolve around. Does that mean the earth and I orbit that center? No, because my effect on the earth is negligible. The absolutely immeasurably small wobble my mass gives the earth is not an orbit. There are bodies much more massive than me that the earth orbits (despite how many Doritos I eat).

To put in less hyperbolic terms, Mars’ moon Phobos and Mars have a gravitational center, deep deep deep within the Martian core that both bodies revolve around. Does that mean Mars orbits this point? I don’t think a reasonable person would say so. A massive body wobbling because of a small body orbiting it is not orbiting. Only one thing in such a system is orbiting.

  • All
  • Subscribed
  • Moderated
  • Favorites
  • •
  • random
  • [email protected]
  • All magazines
    •