Robittybob1

OK so what would you call that? All those bodies and points are on a line, and while they orbit and stay on the line we'd call them stable, but they are prone to be unstable at these 3 Lagrangian Points (L1, L2 and L3), so how do you describe the bodies moving away from these points? They move at a rate wrt that line. Edit: The other points that are on that line are the two - five barycenters depending on the number of objects at the Lagrangian Points along that line.

I think I was just extremely tired. It is not that often that I forget what I write on the science forums.

What I was calling "stationary" was that line on which "the first three Lagrangian points are on the line connecting the two large bodies". If it was still on that line it was "stationary" and therefore I was interested in how fast did it move off that line on an orbital path around the Sun? That would have been its initial speed.

I keep on thinking about the dynamics of that situation. It will work as long as you don't calculate that the centripetal force has to equal the gravitational force. The Sun has just too much inertia to ever be made to orbit the Earth. I can't imagine ever doing the math, but they don't seem to work with the centrifugal forces as much as I think they should. So I am tempted. Thanks xyzt. Here is a paper that talks of gravitational and centrifugal forces solving the Three-body Problem and is just about clear enough for me to give the math a go. Lecture L18 - Exploring the Neighborhood: the Restricted Three-Body Problem http://ocw.mit.edu/courses/aeronautics-and-astronautics/16-07-dynamics-fall-2009/lecture-notes/MIT16_07F09_Lec18.pdf Janus did come up with a very interesting number http://www.scienceforums.net/topic/88515-how-to-calculate-the-force-of-gravitational-attraction-in-co-orbiting-planets/#entry862603 But I always wanted to know if the first loop of the horseshoe orbit was started off at zero km/sec. At least tell us how you got the L3 planet to start moving around the orbital perimeter?

http://en.wikipedia.org/wiki/Lagrangian_point#History Does the phrase "for any three masses" mean that the third one has to be much smaller than the rest? http://en.wikipedia.org/wiki/Lagrangian_point#/media/File:Lagrange_points_simple.svg How does the Sun - Earth L3 point orbit the Earth? "In the Earth's frame" is that like saying "the Sun orbits the Earth in the Earth's frame"? If that is so then the Sun - Earth L3 orbits the Earth too but what a way of looking at the Solar System!

So the distance can be constant but the distance vector is continually changing. What was the point of that question? "Rest" defined by Wikipedia "Rest, in physics, refers to an object being stationary relative to a particular frame of reference or another object." The instability of L3 is not an issue for if Theia started from there it is able to escape the L3 position and move around (in those horseshoe orbits) for some millions of years picking up mass until the orbits allowed for Earth and Theia to collide or for Theia (the Moon) to be captured into an orbit around the Earth. I'll see if I can get someone just to run the Three Body program but I'm not in any hurry. I think the questions from the OP have been answered as best as possible at the moment. Thanks to those who have contributed.

What I was wondering is how do you name a Lagrangian Point? In your above statement the "TWO bodies" are orbiting a barycenter eg the Sun - Earth barycenter or the Earth - Moon barycenter, so when you introduce the third object do we say "at the Sun's Lagrange point" or "at the Earth's Lagrange point" or combination "Sun - Earth system Lagrange point" or the "Earth - Moon system Lagrange point". Everyone up to now just says "at the Lagrange point" but not what system the Lagrange point relates to. So I getting a bit confused if Swansont says the L3 orbits the Earth. http://www.scienceforums.net/topic/88515-how-to-calculate-the-force-of-gravitational-attraction-in-co-orbiting-planets/page-2#entry863348 Which system's L3 orbits the Earth?

All a bit difficult to understand really. It is an interesting concept but impossible to know.

I wonder if that would work when playing golf? That was interesting.

It is a weird thought. Reincarnation and multiple universes opens up endless possibilities, but if we've been here many times before we don't remember do we? So we will never know for sure till we have proof of it.

Which is the implication in #2. It is the brain controlling the arm movement, so when you decide to jab quickly you are less concerned about reaching. So the arm moves differently in both cases.

Have you seen that written down somewhere? The L3 point can be a point hidden behind the Sun from the Earth's frame. I can't see how anyone can say it orbits the Earth sorry. Yes, like those horseshoe orbits demonstrated by Janus they were all wrt the Earth. Both the Earth and the L3 planet orbit the Sun on a yearly basis as well as doing the toing and froing wrt to each other. Well that is the picture in my head at the moment. The planets set themselves up in these positions because they have a degree of stability at these points. The orbital speeds are increased (shortened radius and period) sufficient to overcome the additional apparent central mass due to the associated L3 planet. Each astronomical body has it's own Lagrangian points and I think the ones we a tlking about are the Sun's Lagrangian points. So there are the Earth's Lagrangian points as well as shown in this animation. Here the L3 orbits the Earth but is is a completely different L3 than I'm speaking of in the thread. "lagrange points animation" should really be "Earth's lagrange points animation" The better mathematical approach to the Sun's Lagrangian points is in "The Lagrangian Points are Awesome... Tutorial"

Janus if you are around - in the simulation did you start Theia off at the L3 point from stationary?

http://www.thesaurus.com/browse/theory why did your link say that you'd spelt Theory wrong? Weird!

What happens if ISIS takes over Iran next?

That would be a matter of relativity.

Knowing those rules would be another miracle!

It felt miraculous at the time; to see my post with a word in it that I couldn't recall using at that time. I can't see any similarity between that and the miracles attributed to Jesus.

I usually celebrate using a new word in my vocabulary. It is just that I must have slipped up there. What is this about the rules? Forum rules?

"close isotopically" must be more than just some other spot in the Solar System with close to the exact same ratio of isotopes. Could there be a similar place other than within a co-orbital region?

Isotopical as in "very close isotopically" is a very unusual word for me to use. I do know the word "isotope", but that must have been my first use of the word "isotopically" especially the concept "close isotopically".

Now you are being a softy. We were taught the same, to jab real fast, I thought it was to have your hands back in the defensive position as quick as possible.

That could the fault of the device that is measuring the punch. (That was not supposed to be a joke but is now!)

Have you never done something while tired and forgot that you did it? Let's leave the topic there shall we.