Robittybob1

It is a thought experiment not a exercise in reality!

Which region of a cell would have the right activity?

It is just the difference in the escape velocities from the two locations Terminal Impact velocity (Vt) Vt = sqrt(2*M*G/r1) - sqrt(2*M*G/r2) M current mass of Earth r1 - radius of the Earth (current) R2 distance out to center point of the L4 lagrangian Point which by geometry = radius of the Earth's orbit.

The differences in velocities are proportional to the ratio Escape velocity of the Earth minus the sqrt(2*M*G/r), r being the new starting distance. But remember the 2*M*G parts of the equation remains constant. So at those two specific distances the impact speeds won't be much different as you calculated (as they are relatively similar) but once you compare the distance to the Moon compared to infinity there would be a much greater of difference. From memory that paper said the initial velocity was "<4 km/s" which could include 0, couldn't it? As I have previously said any initial velocity above that which is gained from falling toward the Earth would represent the amount of velocity it had gained from also falling toward the Sun. Well that is my prediction at this stage. The L4 position is 60 degrees ahead of the Earth on its orbit around the Sun so as rough calculation we could say it is 1/6 0f the orbit circumference away from the Earth or 1/3 * pi() * r r = 150 million km or from geometry it is exactly the length of r directly. So the difference in Earth Escape velocities from both positions: 11185.8 and 2305.3 so difference in Earth Escape velocities from both positions, when using current Earth Mass: = 8880.5 m/sec 9687.2 and 1996.4 so difference in Earth Escape velocities from both positions, when using Earth mass 0.75 current mass: = 7690.7 m/sec. So from infinity a mass will strike the Earth at 11185.8 m/sec but from the L4 position at 8880.5 m/sec (current mass)

Are you sure they are approximations? An example please?

What sort of language is that? That wasn't even Aussie slang.

With a bit of luck I'm back to work tomorrow, and I'll do it as I promised. You could have convinced yourself that planets further apart will collide at a higher impact speed. You seem to be a wiz at the latex now. Does it do the calculation or is it just a display?

Yes I didn't expect the atmosphere to slow it down much. Now do the calculation I suggested "the combination of the Earth's escape velocity minus the escape velocity at distance X, y and Z."

No you are right on the money! It would be the combination of the Earth's escape velocity minus the escape velocity at distance X, y and Z. The further out the distances X, y and Z the greater the impact velocity (terminal velocity in my way of saying it). <Terminal velocity> http://en.wikipedia.org/wiki/Terminal_velocity That is exactly what we want. We may never get to a situation where there is no more acceleration. So we are just looking for the "highest velocity attainable by an object in free fall" from those distances starting from zero velocity in the normal direction.

Why are you calculating orbital velocity ? I was wanting terminal velocity. If the Earth and Theia are L3 trojans we already know they have similar orbital velocities to orbit the Sun.

During the last month or so I was listening to the lecture series by Michel van Biezen and he said Venus had been hit by a massive object and completely tipped over. I had previously thought of another way of making the planet reverse its spin, and that was by having a moon spin around it in a retrograde orbit. Once the Moon orbits faster than the planet it can be tidally decelerated until it crashes onto the surface or ripped apart by the forces of gravity when it is closer than the Roche Limit. (However that is said properly) Can you see that working?

So remember the Earth is forming and probably without a magnetic field so the greenhouse effect is being reduced all the time by the rapid loss of the atmosphere. So how much longer do you think the cooling was. You don't want to stick to those ridiculous figures in the OP do you?

You can show this yourself simply by taking a mass and dropping it. Step 1. Drop it from 1 meter. measure its terminal speed. Step 2. Drop it from 2 meters. measure its terminal speed. Step 3. Drop it from 3 meters. measure its terminal speed. ...... Carry that on to infinity. Always the higher the gravitational potential the higher the terminal speed. Can you deny that? OK the change in speed gets less and less as the height increases for the gravitational strength declines in the ratio of 1/(r^2) but it is never zero until you reach what is called infinity.

Can we have a runaway greenhouse gas effect? So even though the power from the Sun is less compared to the radiation from land surface, the atmospheric gases act as a blanket and the incoming heat gets trapped, and hence hinders radiation and the whole situation just gets hotter and hotter. Radiation from the land is reflected back down but the incoming radiation is absorbed by the gas. This type of situation would resist cooling but did it happen?

I got my figures from websites 4.533 Gya for Theia impact and 4.2 - 4.3 Gya for the Zircon crystals. Where did you get your figures? Those other questions 1. Insolvable 2. Will depend on how long it takes Theia to go the half billion kms. 3. Will be in few days time.

60 million years??? is that right? http://www.amnh.org/education/resources/rfl/web/essaybooks/earth/cs_zircon_chronolgy.html difference? That is an interval of 327 - 227 million year period.

Note: you can't use the escape velocity of the current Earth as the terminal speed as the Earth then had not gained its final mass at that stage in it development M could be say 0.75 current mass or thereabouts. I feel uneasy using ratios sorry. you still haven't explained "Impact would occur.... and at ~4.1 bya which largely contradicts all geological evidence." What is this evidence you are talking about?

How can we work that out mathematically using a formula and increase the initial rate to give a realistic time period of roughly say 300,000 years? I see you put the decimal point in the wrong place, did you mean 0.41 billion years??? In fact I don't know what you mean by your last sentence. Could you explain it please? Note you can't use the escape velocity of the current Earth as the terminal speed as the Earth then had not gained its final mass at that stage in it development M could be say 75% or thereabouts.

Yes I should not have multiplied it by 2 thanks for that correction. *(Kicking myself)* It would not have started off at 1 km/sec (it starts from basically zero) so how do the figures work out if you start from 1 km/year?

So that is a list of fallacies. Are they all logical fallacies? For there was no fallacy called "Logical fallacy". I'm not educated in terms that you've used sorry.

unlikely - no all you showed it was unstable. Look at it this way if Theia was at L3 and Earth opposite the Sun both planets are at the L3 Lagrangian point of the other. Earth formed even though it was at the L3 of the other planet, so either way it is possible, but unstable but even then how long would it take to come around behind the Earth it is a total of 942500 km around one half of the orbit and if it started off at 1 km/year it will still take a while to impact even if in the final stages it is moving at 7 km/sec. So it is building up mass and speed on its journey too. No one says the Earth and Theia were fully formed planets at the time of collision.

Examples of logical fallacies and how they fit the definition please.

Out by how much?

I felt it was you who made the claim first, I'm sure I have always left my statements as possibilities. I have never claimed it was true. The "fact" being that it is possible. Like if I say it is possible that Theia formed at L3 and you say that is "impossible". It is you making the claim not me. That is why I have asked you prove that it is impossible.

Of course I read that, and I found it interesting but I noted they didn't say why or if they hadn't considered L3, except of course logically if they did send a probe to L3 they can't communicate with it, as it is behind the Sun, and it is also a long way out to there, so it is technically difficult, so I don't blame them checking out the closer regions first. Call 1 a "logical fallacy" but it is also a fact. If there is no reason to discount it why discount it. They are looking at L4 and L5 points because they are possible, but still without proof that Theia came from there either. It is the Easter break here so it will be a couple of days before I'm back in my office.