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I came across galactic tides while trying to find a new concept for FTL travel for a SF novel. Further research suggests it was just a coincidence, that nobody has ever suggested any possible connection, but for narrative reasons I love the idea that interstellar travel is only possible when the collision of galaxies releases waves of (negative) energy. Is there any vaguely plausible scenario where galactic tides might produce the sort of exotic material necessary to make an Alcubierre drive viable? I dream of astronomers watching the movement of galaxies to predict the moment when surges can be ridden to connect civilizations separated by centuries of isolation...

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    $\begingroup$ They could in your world. Of course in your world literally anything could power FTL travel. It's up to you how you choose to modify/break the rules of physics. As written this looks like something you can make up for yourself however you want rather than a specific answerable question that is a good fit for this site. $\endgroup$
    – sphennings
    Jan 5, 2022 at 20:34
  • $\begingroup$ Doesn't the term 'tides' imply 'gravity'? $\endgroup$ Jan 6, 2022 at 4:08
  • $\begingroup$ Watching the movement of galaxies to predict something will require patience. What's the average life expectancy of your astronomers.. and how much time will your civilization have to wait until good travel circumstances occur ? When intergalactic gravity comes into play, you're talking geological time scales. $\endgroup$
    – Goodies
    Jan 9, 2022 at 10:00
  • $\begingroup$ Haha, yeah, I understand that now. I'm looking into using something else, like supernovas. $\endgroup$ Jan 10, 2022 at 11:03

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the collision of galaxies releases waves of (negative) energy

This isn't really what tides are though. The tidal forces experienced by things approaching a galaxy are the same sorts of tidal forces the sea experiences on Earth... there's no negative energy involved or required.

I dream of astronomers watching the movement of galaxies to predict the moment when surges can be ridden to connect civilizations separated by centuries of isolation...

The problem here is that there isn't a "moment" of galactic collision. Galaxies are Quite Big, and whilst they move about at what seems like quite a high speed they're crossing intergalactic space which is, as the good book tells us, vastly, hugely, mindbogglingly big.

This means that galactic collisions play out over billions of years. Consider the Antennae Galaxies:

Antennae Galaxies

They've been crashing through each other for 600 million years, and would have been experiencing disruptive tidal forces for a good few hundred million years before that. The merger won't be meaningfully complete for at least another few hundred million years. That makes timescales of mere centuries a bit insignificant.

Is there any vaguely plausible scenario where galactic tides might produce the sort of exotic material necessary to make an Alcubierre drive viable?

Not obviously... galactic collisions are exciting things (if viewed over a long enough timescale) but they aren't magic. Stars get chucked into deep space and new stars get formed all the time in regular aeon-to-aeon galactic life, collisions just speed it up a bit.

That's not to say that you need to abandon all hope. You can certainly handwave in that one of the galaxies does, in fact, come with a whole load of suitable handwavium, which didn't exist in the other galaxy. Handwavium-rich stars and stellar systems will go shooting through the boring galaxy, and the close passage of such stars does represent interesting possibilities for nearby sophonts (which include "destruction of their own solar system").

Ultimately if you want FTL travel, you can't do without magical handwaving anyway, so you can feel free to invent a suitable background that fits your plot needs.

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  • $\begingroup$ Thanks very much for a detailed and helpful response! $\endgroup$ Jan 6, 2022 at 6:19

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