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PBS Space Time just did an episode on this topic: https://yewtu.be/watch?v=vyEWLhOfLgQ https://yewtu.be/watch?v=vyEWLhOfLgQ

godd2 3y ago
I'm somewhat surprised he didn't talk about evidence of space-faring ancient civilizations. If humans perish and a new intelligent species comes around in millions of years, they would be able to find stuff we've left on the moon, provided we pepper it all over its surface so as to survive any future meteor impacts.
- xgkickt 3y ago
  Just think of all theories about the bags of mammalian feces left there.
  - throwuwu 3y ago
    Those are the least likely artifacts to last
- jimhefferon 3y ago
  It is the drizzle of tiny particles that wears away.
  - godd2 3y ago
    There are craters on the moon that are billions of years old. Also, we could probably bury tablets and artifacts.
    - smegger001 3y ago
      12 people have been to the moon for about a total human surface time of about 6 days 17 hour mostly spent most of that time spent within a small radius near the six landing sites. and we haven't bothered to go back in over 51 years the number of tablet you would have to bury on the moon for a civilization as advanced as our to find one would be ridiculous you would essentially have to tile the moon in them for us to have guarantee we would have found one of them.
      - ericbarrett 3y ago
        The Lunar Orbiter Laser Altimeter has mapped the lunar surface to, best as I can tell from a quick search, about 1m resolution. So I think a reasonably sized stele or 2001-style monolith would probably have been discoverable at our current tech level.
        midasuni 3y ago
        But we wouldn’t be able to detect human level lunar activity in a million years time. We can barely detect human activity from 50 years ago when we know exactly where it is. I think we are More likely to spot ancient Geostationary satellites, which will have drifted away from a perfect circle but should still be noticeable. LAGEOS aren’t in anywhere near that high an orbit but should survive 8 million years. They have a plaque on them designed by Sagan should a future civilisation find them.
        ericbarrett 3y ago
        You’re right about satellites but I think you’re underestimating how long a monolith could last on the Moon. For something big and built to last, it could be many many millions of years https://bigthink.com/starts-with-a-bang/astronaut-footprints-disappearing-moon/ https://bigthink.com/starts-with-a-bang/astronaut-footprints...
        midasuni 3y ago
        But we haven’t put anything built to last on the moon - rovers and landing stages are very small and relatively fragile A similar civilisation may have gone to the moon, but thanks to irradiation and micrometeorites over millions of years. Footprints and tyre tracks would certainly be gone, and while you could land at an Apollo landing site and detect remains of refined metal, it’s unlikely to be something you could see from orbit with our level of equipment, you’d have to get up close and personal, and we haven’t done that.
        smegger001 3y ago
        How long would it survive as a monolith on the surface before it would appear to be another boulder? How long until it is illegible due to micrometorite abrasions?
- mr_toad 3y ago
  Over millions of years micrometeor impacts, the solar wind and sublimation would erase anything that wasn’t a large monolithic structure.
robbomacrae 3y ago
Kurzgesagt also: https://www.youtube.com/watch?v=KRvv0QdruMQ https://www.youtube.com/watch?v=KRvv0QdruMQ And just like the paper, it acknowledges the challenges in detecting such evidence due to the limited and complex nature of the geological record.

godd2 3y ago

I'm somewhat surprised he didn't talk about evidence of space-faring ancient civilizations. If humans perish and a new intelligent species comes around in millions of years, they would be able to find stuff we've left on the moon, provided we pepper it all over its surface so as to survive any future meteor impacts.

xgkickt 3y ago
Just think of all theories about the bags of mammalian feces left there.
- throwuwu 3y ago
  Those are the least likely artifacts to last
jimhefferon 3y ago
It is the drizzle of tiny particles that wears away.
- godd2 3y ago
  There are craters on the moon that are billions of years old. Also, we could probably bury tablets and artifacts.
  - smegger001 3y ago
    12 people have been to the moon for about a total human surface time of about 6 days 17 hour mostly spent most of that time spent within a small radius near the six landing sites. and we haven't bothered to go back in over 51 years the number of tablet you would have to bury on the moon for a civilization as advanced as our to find one would be ridiculous you would essentially have to tile the moon in them for us to have guarantee we would have found one of them.
    - ericbarrett 3y ago
      The Lunar Orbiter Laser Altimeter has mapped the lunar surface to, best as I can tell from a quick search, about 1m resolution. So I think a reasonably sized stele or 2001-style monolith would probably have been discoverable at our current tech level.
      - midasuni 3y ago
        But we wouldn’t be able to detect human level lunar activity in a million years time. We can barely detect human activity from 50 years ago when we know exactly where it is. I think we are More likely to spot ancient Geostationary satellites, which will have drifted away from a perfect circle but should still be noticeable. LAGEOS aren’t in anywhere near that high an orbit but should survive 8 million years. They have a plaque on them designed by Sagan should a future civilisation find them.
        ericbarrett 3y ago
        You’re right about satellites but I think you’re underestimating how long a monolith could last on the Moon. For something big and built to last, it could be many many millions of years https://bigthink.com/starts-with-a-bang/astronaut-footprints-disappearing-moon/ https://bigthink.com/starts-with-a-bang/astronaut-footprints...
        midasuni 3y ago
        But we haven’t put anything built to last on the moon - rovers and landing stages are very small and relatively fragile A similar civilisation may have gone to the moon, but thanks to irradiation and micrometeorites over millions of years. Footprints and tyre tracks would certainly be gone, and while you could land at an Apollo landing site and detect remains of refined metal, it’s unlikely to be something you could see from orbit with our level of equipment, you’d have to get up close and personal, and we haven’t done that.
      - smegger001 3y ago
        How long would it survive as a monolith on the surface before it would appear to be another boulder? How long until it is illegible due to micrometorite abrasions?
mr_toad 3y ago
Over millions of years micrometeor impacts, the solar wind and sublimation would erase anything that wasn’t a large monolithic structure.

robbomacrae 3y ago

Kurzgesagt also: https://www.youtube.com/watch?v=KRvv0QdruMQ https://www.youtube.com/watch?v=KRvv0QdruMQ And just like the paper, it acknowledges the challenges in detecting such evidence due to the limited and complex nature of the geological record.