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There are a few ideas about getting to another solar system within a humans life time like breakthrough star shot, but that is only a nearby solar system. A galaxy is MUCH further away. Is it even possible to get to another galaxy within a humans lifetime.

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    $\begingroup$ In the world of science fiction, the answer is yes, no problem! In the world of science reality, the answer remains a resounding no. $\endgroup$ Commented Jul 17, 2022 at 19:18
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    $\begingroup$ There is no such thing as an Alcubierre drive, at least not yet. No one has built one. No one has built anything close to Alcubierre drive. No one has even described how to build one without using stuff we don't know how to build / obtain. It's science fiction. $\endgroup$ Commented Jul 17, 2022 at 19:41
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    $\begingroup$ With an ideal antimatter engine (which we dont know how to build or fuel) accelerating at 1 g you can get to Andromeda in 28 years (ship time), but the fuel needed is insane. math.ucr.edu/home/baez/physics/Relativity/SR/Rocket/rocket.html $\endgroup$
    – PM 2Ring
    Commented Jul 17, 2022 at 20:03
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    $\begingroup$ @TheRocketfan As the article to which PM 2Ring linked, you don't even need FTL. You "just" need a rocket that is 99.999999999998% matter/ antimatter propellant and time dilation / length contraction will do the trick. That rocket of course is well into the realm of science fiction. $\endgroup$ Commented Jul 17, 2022 at 20:23
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    $\begingroup$ @TheRocketfan Lentz's drive still has utterly unworkable energy requirements, equivalent to a tenth of the sun's mass for a 200 m bubble. Fusion using the entire sun as fuel couldn't produce more than a fraction of that. Even if that was reduced to the equivalent of 1 g, that's roughly the yield of the Fat Man nuclear bomb dropped on Nagasaki. And that's ignoring the causality issues. There is almost certainly no way to make an Alcubierre drive, with or without exotic matter. $\endgroup$ Commented Jul 17, 2022 at 21:39

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No it is not really feasible for a human to travel to another galaxy as the distances involved are simply too great. Some people will not be happy with that answer, however I believe we should always attempt to be realistic in our expectations.

Some will suggest all manner of schemes like lasers larger than planet Earth or demolition of modern physics and replacement with something (anything) that allows cherished dreams of interstellar flight to come true. Sadly it's not going to happen. And intergalactic journeys are even further removed from reality.

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  • $\begingroup$ This is the easiest answer to the Fermi paradox. $\endgroup$ Commented Jul 17, 2022 at 20:34
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    $\begingroup$ @OscarLanzi Yes. Read 1940s to early 1950s science fiction. Many sci-fi authors back then expected a Moon landing somewhere in the 1960s. The technology was known. Landing people on the Moon was an engineering problem rather than an unknown science problem. $\endgroup$ Commented Jul 18, 2022 at 2:45
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There's nothing in known physics that directly prevents this. You just have to travel really close to the speed of light and you can get anywhere in the universe wihin a human lifetime. In practice however, we have no idea how to do that. The energy required approaches infinity, you'd be a black hole, and the universe may have ended by the time you get there, but besides those small issues it might just be possible. I don't think it's very likely though. Besides the energy issue, you'd need to avoid hitting anything on your journey, even collisions with dust molecules would deliver thermonuclear explosion-like energies into your spacecraft.

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  • $\begingroup$ Why would you be a black hole? Speed doesn't turn you into a black hole: physics.stackexchange.com/q/3436/123208 $\endgroup$
    – PM 2Ring
    Commented Jul 18, 2022 at 15:14
  • $\begingroup$ No, @Oscar, it doesn't work like that. Relativistic mass is irrelevant, unless you collide stuff at huge speeds. Consider: in the rest frame of the solar neutrinos streaming through your body your Lorentz $\gamma$ is over a million, but that doesn't affect the force you feel due to Earth's gravity. $\endgroup$
    – PM 2Ring
    Commented Aug 13, 2022 at 16:48

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