How do you get an object to orbit a point like that? I understand orbiting a body with mass, but an empty (and moving) point in space? Is it possible for a layperson to understand?

It's celestial heaving to.

But with gravity.

An object at the L2 Lagrange point (or at any of the other 4 Lagrange points) is not orbiting that point, but rather orbiting the Sun-Earth system at or near that point.

L2 is dynamically unstable (as are L1 and L3)—the gravitational gradient appears as a broad saddleback, rather than a depression like L4 and L5—so any perturbation will grow, not dampen, but only small corrections are needed to keep an object within that area.

L2 is a point where 2 gravitational pulls combine to help us:
1) With just solar pull, Webb would travel slower than the orbital rate (deg/sec) of the earth because it's in a larger orbit around the sun (like how Mars' orbital period is slower than earths because it's farther away).
2) If we just look at earth's pull, an object here would have a very slow orbit around the earth - very slow since it's so far away (less than one orbit per year). I'm not going to jump into the math here - that book is on my office desk.

When you combine both the solar and earths gravitational pull, the orbital period of an object at L2 is the same orbital period of earth - 1 year.

L2, if I remember correctly is slightly unstable, but manageable...

The moon adds to the computational fun of making these points work well.

A very big step complete. Merci Beaucoup Arianspace. I'll bet a lot of people down in Guyana are breathing easier right now.

But now comes the hardest part; unfolding the origami spacecraft successfully and getting it operational. There are so many steps, so many potential points of failure, no second chances. It's going to be a long month.

[youtube]https://youtu.be/7PHvDj4TDfM[/youtube]

How do you get an object to orbit a point like that? I understand orbiting a body with mass, but an empty (and moving) point in space? Is it possible for a layperson to understand?

It's the same thing. At L4 or L5 the gravitational and inertial forces combine to generate a pus towards the Lagrange point when an object is near that so even if something displaces it a little it will come back on it's own. At L2 the combined forces in the equatorial plane near the Lagrange point push away from the point but that force is very weak as long as you're close (and close is pretty far when you're a million miles from Earth) so it doesn't require much energy to remain in place even if you're deliberately offset from the center of the point a little.

I'm pretty sure it listens to the dit-dah, dah-dit, and when it gets the aural null, it's in position.

How many objects can occupy spots in these parking lots? Is there a protocol for positions?

How many objects can occupy spots in these parking lots? Is there a protocol for positions?

By the way, why is there gravity? Seems like the whole universe operates on it

According to general relativity, gravity is not so much a force (in the context of the fundamental forces of the standard model) as a curve in the spacetime influenced by the mass(es) of (an) object(s).
In my limited understanding, that's why the LHC was such a breakthrough: demonstrating the existence of the Higgs Boson (exactly where it was supposed to be). Part of the theory is that by moving through the Higgs field, it gives some fundamental particles their mass.

You say the universe operates on it, but it's actually the weakest of those forces. It's mostly relevant at larger scales.

Same for electro-weak force (which is mostly the electric and magnetic forces you are used to, but with the "weak" nuclear force added on - I mean who ordered that.

Then strong nuclear force.

Why 3 forces? Are they really just 1 force (the way electromagnetism and weak force used to be thought separate)?

I think physics is still in the "what" phase, not yet ready for "why" - if why actually has any meaning. Its certainly useful to have all 3 forces - without any of them we wouldn't be having this discussion - which brings up the horrors of the anthropoic principal.


Back to gravity: The general relativity explanation is that mass and energy distort spacetime and objects take the straightest like through it that they can.

[youtube]https://youtu.be/cp_7AJseYYc[/youtube]