4 ms·

if gravity were much more we'd be out of chemical reactions that produce the energy to beat the rocket equation.

• api 7y ago
  This is a possible Fermi paradox answer, or at least factor. Maybe the vast majority of habitable worlds are larger than Earth. The inhabitants of those worlds might find space flight too hard or even impossible. They also might have less interest in it since they would make the natural anthropic assumption that worlds capable of supporting life are probably huge like theirs.
  • derekp7 7y ago
    That really makes a lot of sense. Because planets smaller than Earth cool a lot faster, so they lose their molten core and plate tectonics (which keeps land mass rising and out of the water), and also a magnetic shield that keeps the atmosphere from stripping away (like Mars).
    • JohnJamesRambo 7y ago
      I'm going to be hopeful and optimistic and point out that the large planets in our solar system aren't rocky and suitable for life as we know it anyway. Earth is the biggest one and the rest are gas planets. Maybe planets that harbor life (rocky, liquid water, goldilocks zone closer to the sun) usually have low enough gravity for aliens to escape it. This diagram has some exoplanets on it for size comparison- https://en.wikipedia.org/wiki/Circumstellar_habitable_zone#/media/File:Diagram_of_different_habitable_zone_regions_by_Chester_Harman.jpg https://en.wikipedia.org/wiki/Circumstellar_habitable_zone#/...
    • api 7y ago
      Earth might be right at this threshold of small enough for space flight to be practical (still hard, but practical) but big enough to hang onto water and atmosphere.