Astronomical fact of the day
Feb. 17th, 2026 10:23 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
jbananaYou could to jump into space.
OK, that claim needs some backup, doesn't it? You can't jump that high on Earth. Big rockets are needed to get into space here. The moon isn't as big, so you could jump higher but you'd still come back down. We need to go somewhere smaller.
Mars has two moons, Phobos and Deimos, and they're quite small, particularly Deimos. Wikipedia says:
On Deimos you could jump so high you'd never come down, and you'd be stuck out in space for ever. Scary, but then Deimos is named after the Greek god of fear.
Wait a minute - "theoretically" is a weasel word there. I bet most of us can't jump that well. Only elite athletes need worry.
OK, that claim needs some backup, doesn't it? You can't jump that high on Earth. Big rockets are needed to get into space here. The moon isn't as big, so you could jump higher but you'd still come back down. We need to go somewhere smaller.
Mars has two moons, Phobos and Deimos, and they're quite small, particularly Deimos. Wikipedia says:
Escape velocity from Deimos is 5.6 m/s. This velocity could theoretically be achieved by a human performing a vertical jump.
On Deimos you could jump so high you'd never come down, and you'd be stuck out in space for ever. Scary, but then Deimos is named after the Greek god of fear.
Wait a minute - "theoretically" is a weasel word there. I bet most of us can't jump that well. Only elite athletes need worry.
no subject
Date: 2026-02-18 01:10 am (UTC)I wonder how much force is required to noticeably change Deimos's orbit.
no subject
Date: 2026-02-23 08:03 pm (UTC)Mass of Deimos: 1.51×10^15 kg
Ratio of masses: 2.22×10^13
Jumping on Deimos causes an equal and opposite force on both the jumper and Deimos. So I assume that the velocity imparted to each is equal and opposite, and Deimos's velocity would change by 5.6/2.22×10^13 or 2.52×10^-13 m/s which I think works out at less than a millimetre per century.
So one answer to your question is that the amount of force needed is more than a human can supply by jumping.
(Edited for layout because reply by email took all the line breaks out. Grr!)