Very interesting. Another example of a solar sail was mentioned but not seen. In "Star Trek IV" the captain of a starfleet vessel deactivated by the Whale Probe, in his communication with Starfleet Command, said he & his crew were hoping to make a solar sail to keep their ship operational.
Yes, although the screenwriter seems unclear on the purpose of a solar sail, which is propulsion, not power generation. The captain says they have "high hopes" that it will provide enough power to keep them alive.
Interestingly enough, I was listening to the Economist's Babbage podcast and they were talking about this. Their science reporter didn't seem to understand how physics works. The host asked him if the FRBs really were aliens headed in our direction, via a solar sail, how soon could we expect them? The reporter said that given how far away the sources were, it would be billions of years before they got here. Given that it seems likely an alien species wouldn't fire up something as powerful as an energy projector for a solar sail craft until near the time that they were going to be launching such a craft, and that said craft could be traveling at near the speed of light, it seems likely to me that they wouldn't be all that far behind. Figure they do a test of the projector a few years before they launch (and we've picked up the test), and that said craft would be going roughly 99% of the speed of light, then we could (if this is the beam powering a solar sail) expect them to be a decade or so away.
Believe it or not, there are parts of the universe you can see today that you could never reach, even in infinite time, even at the speed of light. Space itself is expanding. The effect is infinitesimally small on a local scale, and gravity overpowers it, keeping planets, stars, and galaxies together. But on a cosmic scale, the effect becomes enormous. At some point, somewhere around 15 billion light years from where you're standing, the cumulative expansion of space relative to you exceeds the speed of light. That is, parts of the universe beyond this point are moving away from you faster than light speed. This may seem like a contradiction of Einstein's Special Theory of Relativity, but it's not: although objects cannot move through space at the speed of light (or greater), space itself can expand at rates far, far greater. Who predicted this? That's right: Einstein, with his General Theory of Relativity, which changed our notions about what space is. So, if someone tells you it could take an infinite amount of time--even at 99.9% light speed--to cross some region of the universe, it could very well be true. If you were a billion light years away from Earth, you'd have to move at 10,000 miles per second just to overcome spatial expansion in order to make progress.
^This is what hyperspace is for Even if we did have FTL travel available, just think of the relativistic time flows. You spend a week traveling 40 light-years to Trappist. Is it a 1:1 time flow ratio? Two weeks or more have passed in real time? Or have you suddenly traveled back a week in real time? I'd suspect it'd be the second scenario.
That's not the argument they were making, however. They seemed to think that aliens would just now be heading towards us.
And for what it's worth, I highly, highly, highly doubt this will turn out to be aliens. But I'd be thrilled to be wrong!
If you could move through space at FTL, yes, time travel and/or continuity paradoxes would ensue. And so you can't. However, it may be possible to get the same result by distorting space to make a ship traverse the 40 light years. If a ship could expand space behind it, and shrink space in front of it, it could get to Trappist very quickly without actually moving through space. No time travel or continuity paradoxes would ensue. This is the basis of the so-called Alcubierre Drive, named after the Mexican physicist who found "warp drive"-like solutions to General Relativity. It's probably our only hope for FTL travel, but it's extremely doubtful that it can be physically realized. Sci-fi possibilities like hyperspace and wormholes are probably entirely fictional.
I agree, and while it won't affect any of us because we'll all be long dead before scientists crack whether the Alcubierre Drive or other method of fast, practical interstellar is possible, it's a sad idea we're limited to Sol for all practical purposes. As to your first paragraph, you're thinking that FTL would result in the third scenario?
<nitpick> We're limited to Sol when you're talking about getting somewhere within a reasonable fraction of a human lifetime. If you go the generation ship route - or even figure out hibernation - then at least the relatively nearby star systems become reachable. And there are a few interesting candidates within, what, fifteen light years?</nitpick>
The mathematics predict that travelling faster than light through space is the same thing as going backwards in time. You would actually be going faster than causality, meaning your typical time travel paradoxes would ensue. But--based on our understanding--it is simply not possible to travel faster than light through space. You can't reach light speed even with an infinite amount of energy, let alone exceed it. However, expanding space (whether the natural kind, or the result of an Alcubierre drive), even though it may result in objects "moving" apart from one another faster than light, doesn't violate causality. Nothing is moving locally faster than light.
