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>Or someone later wouldn't know about us.... outside say an abandoned car floating through space... The cars we left on the moon will still be there. The satel

>Or someone later wouldn't know about us.... outside say an abandoned car floating through space... The cars we left on the moon will still be there. The satellites and trash in orbit would still be there. The satellites orbiting Mars would still be there. We can see clear evidence that life has altered the climate in the past [1]. Anyone looking like we are would notice our mark on the environment. 1) https://en.wikipedia.org/wiki/Great_Oxidation_Event https://en.wikipedia.org/wiki/Great_Oxidation_Event

zaroth 7y ago
Are satellite orbits really stable over millennia? Maybe just the geo-sync ones, but I imagine anything closer will decay in “relatively short order”.
- zamadatix 7y ago
  Depends what you consider "closer". Geosynchronous orbit is 35,786 km above the surface and while at 500 km you get significant decay (order of years to re-entry) while satellites at 1,000 km are estimated to take centuries to re-enter. Extrapolating that anything above the start of medium earth orbit (2,000 km) and out should last a hell of a long time.
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- dredmorbius 7y ago
  Interesting question, and not one I'm finding ready answers to. Among the better: https://space.stackexchange.com/questions/5583/can-an-artificial-satellite-stay-in-orbit-forever https://space.stackexchange.com/questions/5583/can-an-artifi... Low-Earth orbits will decay over periods ranging from years to millennia, based on residual air resistance. Those effects are minimal in geosynchronous orbit, though there's still some residual atmospheric drag which might be significant over millions to billions of years. The period under concern is roughly 5 billion years, at which point the Sun will have ballooned to a red giant, enveloping the Earth. (Increased solar radiance, as well as various cycles and changes on Earth will likely have long made it uninhabitable by life within the next 800 million years or so.) Other effects include solar wind, possible interactions with the Earth's magnetic field, precessional effects caused by the Earth's axial tilt and irregular geometry (to use that word in its literal sense), as well as gravitational perturbation from the Moon and possibly other bodies within the solar system. There's a slight possibility of impacts, though those would be highly unlikely -- space is big, as Doug said, and satellites tiny. Even the Earth only gets wallopped every few tens of millions of years. Though any such impacts might create a sufficient debries field within the orbital zone to affect other satellites. The Geostationary band itself is quite narrow, and preferential placement is above the equator, which would focus placement for potential interaction.
goda90 7y ago
Well, the things we left on the moon could still be struck by meteors and buried under the surface.

zaroth 7y ago

Are satellite orbits really stable over millennia? Maybe just the geo-sync ones, but I imagine anything closer will decay in “relatively short order”.

zamadatix 7y ago
Depends what you consider "closer". Geosynchronous orbit is 35,786 km above the surface and while at 500 km you get significant decay (order of years to re-entry) while satellites at 1,000 km are estimated to take centuries to re-enter. Extrapolating that anything above the start of medium earth orbit (2,000 km) and out should last a hell of a long time.
- deleted 7y ago
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dredmorbius 7y ago
Interesting question, and not one I'm finding ready answers to. Among the better: https://space.stackexchange.com/questions/5583/can-an-artificial-satellite-stay-in-orbit-forever https://space.stackexchange.com/questions/5583/can-an-artifi... Low-Earth orbits will decay over periods ranging from years to millennia, based on residual air resistance. Those effects are minimal in geosynchronous orbit, though there's still some residual atmospheric drag which might be significant over millions to billions of years. The period under concern is roughly 5 billion years, at which point the Sun will have ballooned to a red giant, enveloping the Earth. (Increased solar radiance, as well as various cycles and changes on Earth will likely have long made it uninhabitable by life within the next 800 million years or so.) Other effects include solar wind, possible interactions with the Earth's magnetic field, precessional effects caused by the Earth's axial tilt and irregular geometry (to use that word in its literal sense), as well as gravitational perturbation from the Moon and possibly other bodies within the solar system. There's a slight possibility of impacts, though those would be highly unlikely -- space is big, as Doug said, and satellites tiny. Even the Earth only gets wallopped every few tens of millions of years. Though any such impacts might create a sufficient debries field within the orbital zone to affect other satellites. The Geostationary band itself is quite narrow, and preferential placement is above the equator, which would focus placement for potential interaction.

goda90 7y ago

Well, the things we left on the moon could still be struck by meteors and buried under the surface.