Are there enough trampolines on earth that we could reasonably expect that at any time there is at least one person in the upper part of their jump on a trampoline?
Also people who live in a basement, or cave, or underground complex of some kind, or who are currently caving, … they also aren’t ‘on’ Earth, they’re ‘in the Earth’, … and people currently in submersibles, under the water line, well they’re not on the surface, they’re in or under the ocean or w/e, by this grammatical level of pedantry.
Spent a moment thinking about this and I think there’s an implied definition for what “on earth” means that we intuitively accept but don’t ever really need to state.
If your projected free-fall trajectory both forward and backward in time intersects with the surface of the earth then you are “on earth”.
Standing on the ground? Intersects twice.
Thrown rock? Intersects twice.
Person in an airplane? Intersects twice.
ISS? No intersection.
Incoming impact meteor? One intersection.
The ISS was launched from Earth, in pieces but still it’s of Earth origin, and will eventually fall back to Earth. It’s inside the Earth’s atmosphere and experiences drag. It’s orbit has to be adjusted and maintained.
Yes, that’s all true, but none of that describes its free-fall trajectory. Drag causes it to deviate from free-fall very slightly, and it definitely wasn’t in free-fall when the pieces were launched from Earth
Unless you define “on earth” to be "below the Kármán line. The Earth’s atmosphere is probably to be considered part of the planet, else gas planet like Jupiter get difficult to talk about consistently. Atmospheres don’t have a proper “cutoff”, they just get thinner and thinner until they gradually become insignificant, so some cutoff is going to have to be arbitrarily defined to make the distinction useful.
Karman line could be a good limit sure, but I think the orbit still kinda makes sense to include “on the planet”.
Say for example if the apartheid baby gets his Mars colony thing going, from Earth’s perspective it wouldn’t make much difference if a person is standing on Mars surface or on the orbit - we could say that the person is on Mars.
Hmm, I think this logic kinda fails because if astronauts are “not on earth”, then neither are air travelers.
Astronauts orbiting earth are just couple kilometers higher altitude
I mean 30,000 feet is 9km. The Kármán line is 100km. The ISS is at an average altitude of 400km.
It’s a bit like saying people in planes don’t count as flying because then people on trampolines should count.
Are you saying that people jumping ARE on earth? Because I disagree.
They’re clearly not “jumping” they’re pushing the earth away
That’s relatively true
Are there enough trampolines on earth that we could reasonably expect that at any time there is at least one person in the upper part of their jump on a trampoline?
Also people who live in a basement, or cave, or underground complex of some kind, or who are currently caving, … they also aren’t ‘on’ Earth, they’re ‘in the Earth’, … and people currently in submersibles, under the water line, well they’re not on the surface, they’re in or under the ocean or w/e, by this grammatical level of pedantry.
We already have a definition for this, the Karman line.
Spent a moment thinking about this and I think there’s an implied definition for what “on earth” means that we intuitively accept but don’t ever really need to state.
If your projected free-fall trajectory both forward and backward in time intersects with the surface of the earth then you are “on earth”.
Standing on the ground? Intersects twice. Thrown rock? Intersects twice. Person in an airplane? Intersects twice. ISS? No intersection. Incoming impact meteor? One intersection.
The ISS was launched from Earth, in pieces but still it’s of Earth origin, and will eventually fall back to Earth. It’s inside the Earth’s atmosphere and experiences drag. It’s orbit has to be adjusted and maintained.
Yes, that’s all true, but none of that describes its free-fall trajectory. Drag causes it to deviate from free-fall very slightly, and it definitely wasn’t in free-fall when the pieces were launched from Earth
Unless you define “on earth” to be "below the Kármán line. The Earth’s atmosphere is probably to be considered part of the planet, else gas planet like Jupiter get difficult to talk about consistently. Atmospheres don’t have a proper “cutoff”, they just get thinner and thinner until they gradually become insignificant, so some cutoff is going to have to be arbitrarily defined to make the distinction useful.
Karman line could be a good limit sure, but I think the orbit still kinda makes sense to include “on the planet”.
Say for example if the apartheid baby gets his Mars colony thing going, from Earth’s perspective it wouldn’t make much difference if a person is standing on Mars surface or on the orbit - we could say that the person is on Mars.
i’d say being in orbit is arguably the least on a planet can be, since an orbit is specifically continuing to miss falling onto the planet.
They would be in Mars orbit, but not planetside. “At Mars” might be a middle ground designator.
Let’s make some artificial rule like you need to be not on earth for 48 hours to be not on earth or something …
Can be at rest in your own reference frame without falling to earth?
From your own reference frame, wouldn’t earth be falling to you? Because then this’d apply to everyone, always.
Can I define my reference frame any way I want? Because if so, yes. And also no
I think better would be to include Earth’s orbit as “on Earth”. This makes sense even if we expand our scope of operations to other planets
The Moon is not on Earth.
The moon and earth are “on” a shared center of gravity. It just so happens to be inside to earth, so meh, we win.
When I jump, I am not in earth.
No, you’re over Earth.