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Started off good and then lost me when he talked about using them for stepping stones to the stars. I'm confused about that. A rogue planet in itself makes a t

• jerf 12y ago
  At the moment, the most feasible way I see to the stars is via laser-launched ship. The cruel mistress that is the rocket equations don't favor even a self-contained starship driven by 100% efficient antimatter reactions, to say nothing of things that might actually work. Leaving your engine behind is almost a necessity. But even if you try to launch things from a solar-system based laser station the physics still don't really work out well. Light-years is a long way to maintain a focus for the beam. Some have decided this means star travel is impossible; I say it just limits how quickly we can do it. We could launch very large ice asteroids with nanotech unmanned fusion stations that construct lasers ("vigorous handwave about magic here") and create ourselves a series of stepping stones to a star. It would take a long time, not least of which is because we would also need to set up the "stepping stones" to stop us on the other end, too! But in theory it seems like it would "just" be a matter of time. Lots of time. But a whole star system on the other end! It's a pretty big payoff for a strapping young Kardashev II civilization. (Note that "just send information" only works after you deliver a physical package to the other end which would be capable of receiving it and doing something with it, and even nanotech is unlikely to be able to land anywhere to begin its lengthy self-replicating process to bootup civilization on the other end if it's merrily passing through a system at 80% the speed of light relative to the local rest frame.) If you were lucky enough to stumble on to one of these planets in the way, it would provide a pretty nice shortcut to setting up your bridge by providing you a nice, huge power source (if you can find a lot of hydrogen lying around somewhere, which is a reasonable guess) that's already more-or-less at rest in the galactic frame, allowing you to use it to relatively easily create more stages on the enormous pipeline, and allowing you the ability to relatively easily replenish the stages in the middle. (If that's even desirable... perhaps the stages can be retargeted to other stars or something once the bootstrap package is successfully delivered.) ... of course, the article's starting with "10,000 years in the future" is probably not a terrible guess about all this, as such things go. This is a guaranteed-slow process, trading time for space. Tell your great-grandchildren to ask their great-grandchildren how the initial plans to make the initial plans for all this are going, and say "hi" to the future for you. Saying "we" will do this might very well be considered to be rather impudent of me, much like Napoleon trying to claim some sort of perceptible credit for the Hoover Dam.
  • meric 12y ago
    It is possible for an observer to accelerate uniformly from their own perspective for an indefinite period of time in special relativity (the motion traces out a hyperbola in spacetime asymptotic to the lightcone). The person undergoing the acceleration doesn't notice anything changing as time goes on. All of the relativistic slowing down and time dilation effects etc. that you mention are seen in an inertial reference frame looking at the accelerating ship. http://physics.stackexchange.com/questions/53587/if-a-space-ship-accelerated-constantly-would-its-astronauts-constantly-feel-the http://physics.stackexchange.com/questions/53587/if-a-space-... From the ship's frame, the acceleration would continue at the same rate. However, due to Lorentz contraction, the galaxy around the ship would appear to become squashed in the direction of travel, and a destination many light years away would appear to become much closer. Traveling to this destination at sub-luminal speeds would become practical for the onboard travellers. Ultimately, from the ship's frame, it would be possible to reach anywhere in the visible universe, before the ship has time to accelerate to light speed. http://en.wikipedia.org/wiki/Space_travel_using_constant_acceleration http://en.wikipedia.org/wiki/Space_travel_using_constant_acc... If you can build an engine that can constantly accelerate, without having to constantly throw fuel behind you, e.g. http://higherperspective.com/2015/03/nasa-engine.html http://higherperspective.com/2015/03/nasa-engine.html, an astronaut can potentially travel 4 light years in less than 4 years, from their point of view, because although from Earth's reference point of view they will always be less than c, as their speed approaches c from Earth's point of view, there will be time dilation between them and Earth. If from Earth's point of view they take 4 years and a bit to travel 4 light years, assuming acceleration to very close to c very quickly, you as an astronaut will experience the same time as a lot shorter, possibly as months. From the astronauts point of view, they can travel one light year in less than one year, if they can accelerate constantly fast enough without dying. Of course I haven't taken into account the amount of energy that needs to be involved, except to say, if you're talking about a one-way trip, the time factor can be overcome, through technology that isn't that impossible. If you know what's on the other side and it's possible can build a self-sustainable colony, colonising other planets is perfectly feasible from a psychological point of view given we have the technology we can accelerate close to c and decelerate from c, by achieving the time dilation effect.