Saturday, December 07, 2019

[ezmpildy] Intragalactic versus intergalactic

The distance between galaxies seems not that much greater than the size of galaxies.  Milky Way diameter 100,000 ly.  Distance to Andromeda 2.5 million ly, so scale factor of 25.  This means (maybe) that after becoming a galactic civilization, it's not that much more difficult to then become an intergalactic civilization.  Star Trek (and others) are unrealistic in limiting themselves to just one galaxy.

Compare this with other cosmic distances:

Half-circumference of earth (farthest possible distance between any two points on earth): 20,000 km.  Minimum distance to Mars: 55 million km.  Scale factor 2750.  Going from being a planetary civilization to being an interplanetary civilization is difficult.

Size of solar system, defined by semimajor axis of Neptune's orbit: 4.5e9 km.  Distance to Alpha Centauri: 4e13 km.  Scale factor 9000.  Going from being a solar-system spanning civilization to being an interstellar civilization is difficult.

These distance ratios don't take into account the difficulty of escaping gravity wells.  Don't know if it matters.

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