Robittybob1

Janus - I'm so happy to hear you can run the simulation. Are they crossing their orbits in that simulation? If Theia's mass was different would the results be different? The other thing to consider would be the drag planets would experience at times they are speed up, the protoplanetary disc would not be fully cleared at this stage. "Giant Impact" happened after about 30 million years didn't it? So can you run the simulation for at least that long please?

There were a couple of papers that might have given me clues but drat they weren't ones free to read. Now I did a division of the Sun's mass by the Earth's mass and it was a surprising 333,000 times more massive. So will it a piddly planet with the mass of Theia have much effect? But instability is what we need in the end for Theia has to come around to impact the Earth. So instability is really good. It is the time that it will take that is important, for that time still gives Theia the opportunity to pick up sufficient mass. How can we estimate the time this would catch-up could take take?

If there was a planet the size of "Theia" at Earth's L3 point how much closer to the Sun would that make the Earth orbit?

The equation produces reliable results. Thanks.

Very good and thanks to you both. I can follow that perfectly now. Thanks I had converted the 150 million km incorrectly to meters. My mistake. My answers should have been 11185.8, 72.899, 11112.9 9687.2, 63.132 , 9624.0 But we will need to look at the work by Janus and make other corrections.

Israel and Iran need to sit down and talk peace.

Where did the [math]\frac{Vt^2m}{2}[/math] bit come from for the Earth? Could you please go over this part with more detail to the algebra so I can see how you get there please? "At r2, we assume that it starts with a v of 0, so this reduces to [math]-\frac{GMm}{r2}[/math] At the Earth's surface(r1) this will be [math]\frac{Vt^2m}{2}-\frac{GMm}{r1}[/math] The "m"s cancel out and solving for Vt gives us [math]Vt = \sqrt{2GM \left ( \frac{1}{r1}-frac{1}{r2} \right )}[/math]" Some of the problem might just be the way the formulas displayed Vt = Terminal velocity OK and the "frac" bit is a mistake in the way the fraction 1/r2 should display.

So in your understanding what is it that you have calculated here?

Strangely I saw the graphs of the roots this time but I didn't see them on the other thread about Dark Matter. Thanks I might have entered the distance in wrongly to my Excel calculation.

You frustrate me. Of course I read what you write and notice you ask the same questions over and over again. So was that your Escape velocity from the Earth at 150 million km? My figures may be wrong but I'll check them tomorrow but be as clear as you can about what you have calculated please.

Assuming you dome the math right this extra force has to be balanced by a shorter orbital period and a shorten orbital radius as a consequence.

I think you are on the right track. I'll see if I can get a paper discussing this to get an idea where I need to go next.

Show me your figures and I'll compare them to mine tomorrow when I'm back in the office please.. Don't take the fact that I'm calculating the impact speed from the L4 or L5 is any indication that I agree with you. I'm Just trying to show you that you are wrong, really.

OK we have talked about the L3 point as well but more recently you were telling me that Theia was more likely to come from the L4 or L5 position. Sqrt(2*M*G/r1) - sqrt(2*M*G/r2) is just one escape velocity minus another.

It was you who has used the 300 million km figure not me. Well you tell me how far it is between the Earth and the L4 Lagrangian point? In this thread we are discussing the L4 or L5 points not the L3 point. I Have already told you we are not "subtracting the square roots of escape velocities at different distances". Get that right first please.

That can't be the whole answer. Initially the forces are balanced, and there is no closing speed. What are the distances you were using? We will try and keep this thread just learning how to calculate the three questions in the OP only.

But what distance are you measuring? I still think I'm right.

Where does the 3*10^11 come from in your calculation? Haven't you seen that been done before? That is pretty standard. You didn't like terminal velocity, and rightly so, so I described what we are looking for even better terminal impact velocity. I am just calculating escape velocity , not the square root of escape velocities. or you could say velocity at the point of impact.

It probably has to do with being unregistered at the Wolfram site. Are those x values read where the graph crosses the x axis?

Wow what a topic! I hope someone comes and discusses it with me. It has huge ramifications. Was Theia once at the unstable L3 position? Pointless having it a a stable spot (L4 or L5) as it could still be there if that was the case. There isn't much on this on the web so it will need original calculations to work through it, but the L3 position seems to have a simplicity that we might be able to cope with.

You lost me there sorry. All I see is what looks like an equation that is being rearranged. 510998=((938272046-x)/2)*√(1-(x^2/938272046^2)) So there is still an X in it, so how can you say you've solved it?

What were the three decimal places? Show me Ground potential defined to 3 decimal places please?

I'm using Excel and formulated cells so the same information is going into all the calculations. It is hard to make an error with Excel.

How do we calculate the force of gravitational attraction between co-orbiting planets? Take 2 planets both the same radius from the Sun and have them start off at the L3 lagrangian position with respect to each other. (That is directly opposite each other on different sides of the Sun.) Now if for some reason one or the other is perturbed and and they get off the L3 Lagrangian Spot and hence over time they get pulled around the orbital circumference toward each other, but at the same time both are still orbiting the Sun. This is definitely not the same as two bodies separated by a distance 2 times the radius, because that was where they start from and they didn't move toward each other until they were disturbed. Has anyone got any idea how we could solve: 1. how long it would take to come around and 2. what is the closing speed when they finally meet up with each other? Help will be most appreciated. Are there any clues please. http://www.popsci.com/science/article/2011-02/two-planets-discovered-sharing-same-orbit What keeps the planets from attracting to each other? This is ultimately what I want to know: "Did Earth Once Share Its Orbit with a Mars-Sized Planet? New Kepler Data Suggests "Yes"" http://www.dailygalaxy.com/my_weblog/2011/02/-did-earth-once-share-its-orbit-with-another-mars-sized-planet-new-kepler-data-suggests-yes.html This YT just about enabled me to understand Lagrange Points "Lagrange Points - Sixty Symbols" Now that was amazing for up till then I was lost in space!

Can you Google the word Lysosomes?