Science a GoGo's Home Page Forums General Discussion General Science Discussion Forum Did Earth coalesce from 2 medium sized planets?

Yeah, but it is fun. It's why I've come to this forum - I love science, love to debate science, and the people here seem to be above-par compared to other forums I checked out before deciding to come here.



Happened all the time while our solar system was forming. If in separate orbits gravitational tugs from the larger planets (or even a close pass or impact by a smaller one) could create a situation where there would be an impact.

Another possibility is what is thought to have happened in the case of the moon. The moon is thought to have accreated in the earths L4 or L5 point. This co-orbital position is stable until the smaller partner gets to be ~10% of the mass of the larger. At this point the orbit is no longer stable, the smaller mass slips out of the L-point and, according the the papers I read, a collision is now inevitable due to the closely spaced, but now separate, orbits.

Finally, if you had two planets in the same solar orbit, with the two planets orbiting a common center of mass, I think a collision would also be inevitable. Tidal forces would cause the two planets to spiral outwards from each other, until eventually one escaped into an independent orbit. Alternatively (or perhaps more likely) gravitational tugs from the sun and other large planets (Jupiter?) would eventually disrupt the system. Once disrupted its only a matter of time until the new solar orbit crosses the old - wham, bam, thankyou mam!




???how do you figure, that opposite of how gravity normally works???



As I said above, tidal forces and/or tugs from other masses in the solar system can break apart such systems. Once again, we need a real astronomer to comment, but I believe such co-orbits are fundamentally unstable; especially when the co-orbiting pairs are in orbit around a much larger mass (i.e. the sun).

Bryan