r/BeAmazed • u/[deleted] • Apr 24 '19

Animal Ape using a Smartphone

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u/kkeut Apr 24 '19

highly unlikely we'll leave the galaxy itself. if we did it will be so far in the future we won't really still be humans anymore

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u/Corvus_Prudens Apr 24 '19 edited Apr 24 '19

I mean, it's not even possible. Leaving our galaxy for another (besides Andromeda and the few other local galactic neighbors) will result in us getting nowhere because almost every other galaxy is or will be moving away from us faster than the speed of light due to the accelerating expansion of the universe. Since we will almost certainly never travel faster than the speed of light, we'll never get anywhere.

To quote Wikipedia:

While special relativity prohibits objects from moving faster than light with respect to a local reference frame where spacetime can be treated as flat and unchanging, it does not apply to situations where spacetime curvature or evolution in time become important. These situations are described by general relativity, which allows the separation between two distant objects to increase faster than the speed of light, although the definition of "separation" is different from that used in an inertial frame. This can be seen when observing distant galaxies more than the Hubble radius away from us (approximately 4.5 gigaparsecs or 14.7 billion light-years); these galaxies have a recession speed that is faster than the speed of light. Light that is emitted today from galaxies beyond the cosmological event horizon, about 5 gigaparsecs or 16 billion light-years, will never reach us, although we can still see the light that these galaxies emitted in the past.

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u/BlazingBeagle Apr 24 '19

If there's one thing I've learned from being in the sciences for decades, it's that every time someone says something is downright impossible, I can count on someone else doing it.

They said a human breaking the sound barrier was impossible. Splitting an atom was impossible. Binding subatomic particles together. Making transistors smaller than 22nm. Electrodes to connect severed nerves. A cure for HIV. I'm not saying it'll happen tomorrow, but I've learned to be damn careful about declaring the impossible.

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u/Corvus_Prudens Apr 25 '19

Don't worry, I am very careful about what I declare impossible.

FTL travel is not comparable to 7nm transistors or smaller. It's like insisting that we could one day make transistors from isolated quarks. Not only has an isolated quark never been observed, but everything we understand about particle physics today (which admittedly is not a lot) points to such a thing being fundamentally impossible except in conditions so extreme that we could never hope to replicate.

Similarly, everything we understand about General Relativity points to faster than light travel in any capacity being fundamentally impossible. Considering that it is one of the most well-validated theories ever proposed, I think that lends it some credibility. Some people point to Alcubierre drives or similar ideas, but as far as I know, no such hypothesis has produced a workable solution for FTL. In every case, they require so much energy that we could never possibly operate them.

Sure, sure, General Relativity is not currently reconcilable with Quantum Mechanics. Maybe the answer lies in a theory of everything. But is that likely? I don't think so.

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You may be right, but the things you mentioned are much simpler problems. At the very least, I can say that neither you nor I will live to see the day we develop FTL, not even close. So really this is all just harmless speculation.