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I don't think it would take generation ships. At 40C, a 10-year mission gives you a 400ly baseline. (10 years seems reasonable, indeed conservative. We're running deep-space astronomical missions longer than that right now -- Cassini, Mars Odyssey, I'm not even mentioning the Voyagers.)

At that point a "parsec" -- a second of parallax against the deep background -- is now ~80 Million LY. (Yes, really. Right now we have a one au baseline, and a parsec is about 3.1 ly or ~200,000 au.) So, we'd be able to do very precise astrometry for our Local Group, and get reasonably precise measurements out to half a billion LY or so. None of this "standard candle" stuff.

Also: in round numbers, the galaxy is about 1000 ly thick, and the Sun is currently more or less in the middle of it. (Though this changes over time.) So, it would be a 10-15 year trip to get outside the galaxy.

Doug M.

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james_davis_nicoll

James Nicoll Reviews

May 2025

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