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Well, an unperturbed orbit is straightforward and deterministic. But three+ body problems (which I believe the original comment is describing) do not have close

Well, an unperturbed orbit is straightforward and deterministic. But three+ body problems (which I believe the original comment is describing) do not have closed form solutions and are general simulated: https://en.wikipedia.org/wiki/Three-body_problem https://en.wikipedia.org/wiki/Three-body_problem. The reason planet nine is suspected to exist is due to the commonalities in the orbits of trans-neptunian objects. That is, there appears to be a large gravitational influence on TNOs that causes the distribution of their orbits to exhibit irregularities that don't make sense with only two factors influencing their orbits.

analog31 7y ago
Indeed, and it's worth generalizing that the vast majority of contemporary problems do not yield themselves to closed form solutions. We are constantly finding numerical solutions. If you went to college when I did, first of all, you're eligible to join the AARP, and second, the problems that you studied were overwhelmingly solved in closed form. This was true in math as well, both in college and at the K-12 level. Now, are ML algorithms worth adding to our tool belt of numerical methods? Oh, probably. When the fad is over, some useful applications will remain. We already use regression a lot, and that's a primitive form of ML.