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The moon is much less dynamic than the earth, which could be covered in jungles or ice or something that makes it difficult to detect the (former) presence of i

The moon is much less dynamic than the earth, which could be covered in jungles or ice or something that makes it difficult to detect the (former) presence of intelligent life. IMO it's plausible that aliens might find artifacts on the moon that would then prompt a more in-depth exploration of the earth.

jsmthrowaway 10y ago
The zillion artificial satellites and other crap and debris orbiting the bigger, lusher body is probably a hint to said explorers, even with atmospheric orbital decay and perturbations over a long time scale. Earth orbit is our calling card for some time, even if we all die. Especially if they have decent midrange sensors to display nearby craft, Earth will look like a swarm of bees. Run any orbital debris simulator if you don't believe me. It's a mess up there.
- deleted 10y ago
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- schwarrrtz 10y ago
  That's a good point. Found an interesting article about this: > Orbits tend to decay over time, at a rate determined by the initial altitude. Anything above 2,000 km will take millennia to return to Earth, while satellites further down might take centuries or decades. http://www.slate.com/articles/news_and_politics/explainer/2005/04/where_satellites_go_when_they_die.html http://www.slate.com/articles/news_and_politics/explainer/20...
  - jsmthrowaway 10y ago
    There are faint, faint wisps of Earth's atmosphere a fair distance out, which is the big part of an orbit's challenge. Perturbations from other bodies nearby (notably the Moon), deformities of Earth's gravity, and even solar weather and tiniest fractions of gases are other contributors on a long-enough time scale. Micrometeorites would probably be the big risk over time for our orbital monument to humanity, and I would expect Kessler syndrome, as dramatized in Gravity, to actually happen over a long enough period without human existence. (Hell, even with us around it's a possibility, but not as depicted in the film. It'd be slower. Some say it's already underway.) Distant orbits might decay away from Earth given enough time and certain circumstances, oddly enough. A return to Earth is not guaranteed.
    - FreeFull 10y ago
      The Moon itself certainly is gradually moving away from Earth (and slowing down Earth's rotation in the process)
      - jsmthrowaway 10y ago
        Indeed. That's one of those science nuggets I love telling people because it's universally accessible and blows everybody away. Suddenly makes galactic timescales and gravitation real for people. (Or they're just being nice to me...)

jsmthrowaway 10y ago

The zillion artificial satellites and other crap and debris orbiting the bigger, lusher body is probably a hint to said explorers, even with atmospheric orbital decay and perturbations over a long time scale. Earth orbit is our calling card for some time, even if we all die. Especially if they have decent midrange sensors to display nearby craft, Earth will look like a swarm of bees. Run any orbital debris simulator if you don't believe me. It's a mess up there.

deleted 10y ago
[deleted]
schwarrrtz 10y ago
That's a good point. Found an interesting article about this: > Orbits tend to decay over time, at a rate determined by the initial altitude. Anything above 2,000 km will take millennia to return to Earth, while satellites further down might take centuries or decades. http://www.slate.com/articles/news_and_politics/explainer/2005/04/where_satellites_go_when_they_die.html http://www.slate.com/articles/news_and_politics/explainer/20...
- jsmthrowaway 10y ago
  There are faint, faint wisps of Earth's atmosphere a fair distance out, which is the big part of an orbit's challenge. Perturbations from other bodies nearby (notably the Moon), deformities of Earth's gravity, and even solar weather and tiniest fractions of gases are other contributors on a long-enough time scale. Micrometeorites would probably be the big risk over time for our orbital monument to humanity, and I would expect Kessler syndrome, as dramatized in Gravity, to actually happen over a long enough period without human existence. (Hell, even with us around it's a possibility, but not as depicted in the film. It'd be slower. Some say it's already underway.) Distant orbits might decay away from Earth given enough time and certain circumstances, oddly enough. A return to Earth is not guaranteed.
  - FreeFull 10y ago
    The Moon itself certainly is gradually moving away from Earth (and slowing down Earth's rotation in the process)
    - jsmthrowaway 10y ago
      Indeed. That's one of those science nuggets I love telling people because it's universally accessible and blows everybody away. Suddenly makes galactic timescales and gravitation real for people. (Or they're just being nice to me...)