Gravity calculations I should be able to do

[Chronos]

Actually, you always have to take both masses into account, unless one is so much more massive than the other that it doesn’t matter to the accuracy of solving the problem. (A bowling ball falling towards the earth.)

Unless you’re working to extreme precision, the Earth falling into (or around) the Sun is also such a case. Heck, even Jupiter is less than 1% the mass of the Sun.

[Leo_Bloom]

@iamnotbatman

If you picture the motion to be a circle on the X-Y axis with radius 1 AU, then when the earth is at X=1, you can see that Y=0. Go a quarter of the way around, then X=0, and Y=1. The point is to think of the earth as “falling” from X=1 to X=0, ignoring the Y-coordinate.

Thanks. Got it.

[Leo_Bloom]

@SlowMindThinking

… Both objects are perpetually falling towards that center of mass but, Adamseque, they just keep missing.

Got your point, but I don’t get reference “Adamseque.” Sounds nice. What is it?

[Chronos]

“Adamsesque”: “In a manner reminiscent of that described by Douglass Adams”. In the Hitchhikers’ Guide to the Galaxy books, he explains that the secret to flying is to throw yourself at the ground, but miss.

[Andy_L]

Just learned the term for this calculation - “free-fall time”. This article confirms the calculations we made above and talks about other uses for it Free-fall time - Wikipedia