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You haven't accounted for the massive gravity well that is the sun. The difference in potential energy from infinity to the radius of Earths orbit is GMm/r. Set
by IIAOPSW 4y ago
You haven't accounted for the massive gravity well that is the sun. The difference in potential energy from infinity to the radius of Earths orbit is GMm/r. Set that equal to momentum (.5mv^2) and you get sqrt(2GM/r). Plug in the numbers and you'll see you can't really have a meteor that stumbled in from outside the solar system with a similar velocity to Earths orbit by the time it came down to Earths orbit. Put another way, if it was moving slow enough for the speeds to basically match, it would also be in an orbit around the sun similar to our own, and you'd have to account for the missing potential energy it had before entering our stars gravity well. If you want to argue it came from within the solar system, it would have to have already been in an Earth like orbit this whole time, so why don't we see it?
- titzer 4y agoOrbital mechanics is considerably more complex than this because there are several over massive planets orbiting the Sun. Granted, the odds are very low of getting kicked into a trajectory that will just barely kiss Earth's orbit (at the right time), but it can happen. Not everything orbits in a conic. Also, extrasolar meteors are probably a lot more rare than the above comment would suggest.
- IIAOPSW 4y agoThat is so unlikely if it happened I would seriously consider the possibility of an intentional gravity maneuver by an alien race.
- roywiggins 4y agoNear-earth asteroids periodically wander into temporary orbits around the Earth and then wander off. https://earthsky.org/space/2020-so-mini-moon-asteroid-or-space-junk/ https://earthsky.org/space/2020-so-mini-moon-asteroid-or-spa...
- eternalban 4y agoThanks for the link. "Strange space object 2020 SO was discovered on September 17, 2020, on approach to Earth. On November 8, it slowly drifted into Earth’s sphere of gravitational dominance, to become a new mini-moon. It’ll escape back into a new orbit around the sun in March 2021. During that time, it’ll make 2 large loops around our planet." Why would it leave orbit if it already does 2 circles?
- xbar 4y agoThink of them as increasingly elongated elipses and you can imagine the instability building...
- roywiggins 4y agoThey're orbits, but not stable ones. Not even really ellipses. By the time it's made one orbit-ish motion around the planet, the moon has moved relative to it. The second go around it gets affected by the new position of the moon. Eventually the combined effects of the moon and the sun's changing relative positions will nudge it out of orbit.
- VLM 4y agoYou all in the comments are rediscovering Lagrange points the hard way. L4 and L5 are stable, BTW, and we have a relatively famous space telescope at L2 which requires active stability control to stay there. https://en.wikipedia.org/wiki/Lagrange_point https://en.wikipedia.org/wiki/Lagrange_point
- eternalban 4y agoThanks. I wonder if something similar is responsible for the gaps in atomic orbitals. https://upload.wikimedia.org/wikipedia/commons/d/d0/Lagrangian_points_equipotential.gif https://upload.wikimedia.org/wikipedia/commons/d/d0/Lagrangi...
- rvba 4y agoThis made me think how the moon's orbit remains stable after so many small objects fly around. I guess they are too small to be significant enough (obviously good).