They run the orbits backwards. Gravitationally forced dynamics works as well with time running backwards as forwards. Then when two, or usually more, objects "come together" in reversed time, they rule that a either a collision or at least a strong gravitational interaction, which change orbits. They have to take into account the gravity of the Sun and the planets. Although they could ignore most all but Jupiter most of the time, unless the object gets "close" to some other object. Where "close" depends on the size of the other object.
Some of the people who do this work for a different division of my employer. See 'em on National Geographic, History Channel, etc, all the time.
Thanks for that explanation. The universe is a pretty cool place, isn't it? I wish I understood more about it.
How the heck do you know what came from where in the first place?
They run the orbits backwards. Gravitationally forced dynamics works as well with time running backwards as forwards. Then when two, or usually more, objects “come together” in reversed time, they rule that a either a collision or at least a strong gravitational interaction, which change orbits.
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Thanks for the answer.. but how do they know that they are looking at the same two objects over time? They do allude to that happening when more than two may be involved, pretty good science any way ya cut it.. ;-)