Slashdot Mirror
Optical Levitation, Space Travel, Quantum Mechanics and Gravity
An anonymous reader writes "Light doesn't just make things brighter; it can also push things around. Normally this "radiation pressure" force is so small you don't notice it. But if you get a really big mirror then you could use it to power a space ship to the stars. This is the idea behind solar sails. The impact of light is more obvious on small things. Scientists are thinking about levitation of a mirror that would be large enough to see with the naked eye. If this turns out to work, the motion of the floating mirror could be used to probe the physics that connects quantum theory and general relativity."
A trip to the nearest stars with the speeds attained by Voyagers I and II and then some, at the limits of our technology, would take on the orders of 70,000 Earth-years. Should it be done? Hell yeah! Do you expect to be alive? Hell no! But with huge solar panels living off of starlight per person carried, you could take a human colony into orbit to the nearest stars, and they could live there for millions of years. Mind you written history is like 8000 years old (Egyptian Pharaoh's and hyeroglyphs, or 11-13000 if you go with the Sanskrit writings), and modern humans (Omo remains) have only been around for 200,000 years, so a 70,000 year trip is quite a trip. But, you never know, humans on Earth may develop an AI that kills everyone, or a super intelligent genetically modified biotech photosynthetic microorganism that kills everyone and everything including trees, grass, lions, deer, fish.. and emerges as the "winner" back home as the only surviving species, well, at least these folks far away would be safe, at least for a while, till this super intelligent life form chases them down too and eats them too. But at least they get some time to figure out how to defend and stand a chance, possibly by creating their own, friendly superintelligent artificial intelligence silicon/organic android microbe that's better than themselves so it could kill them, but luckily it doesn't, but like a good guard dog, protects them from the attacks of the Earth based microbe, that come after them in say, 1000 years (if they have figured out a 70x faster ways to make the same trip.) See a thousand years is a long time to think things through.
The propulsion system should use extra-solar system harvested hydrogen atoms (they are like 1 H atom per cubic mile or something like that), accelerating it to near speed of light through special cyclotrons, then as the relativistic mass takes over and things get out of sync, special coiled linear accelerators continuing it, and you can get almost any kind of mass out of each atom, and get a great propulsion kick, impulse out of each, for rotation and speed control, or for further accelerating, being mindful that halfway through the trip you have to start decelerating, and such propulsion would still beat the simple light propulsion by orders of magnitude, because the impulse per energy expanded ratio is much better than with simple light. It's true that you're creating mass out of energy as you build the mass of each proton up, and shooting off pure energy as mass is equivalent to shooting off pure light as mass, so there is an optimum velocity, optimum ejection speed dependent on the economics of harvesting each atom from the really thin galactic vacuum vs. economics of not building up too much relativistic mass into it and wasting energy as mass, as in case of a light propulsion. You may have to resort to pure light propulsion in case you cannot find any hydrogen atoms whatsoever within 100 cubic miles or so, such as intergalactic space.
In closer quarters, on rotating cylinder space modules near Earth orbit or Lunar orbit, such propulsion, including light propulsion is pure absolute economic waste, compared to specific impulse gained per size (mass, volume) of the drive, as we have plenty of matter to waste, if nothing else, solar wind close to the Sun is pretty matter rich, visible with things like Aurora Borealis. In particular even a cyclotron drive on a rotation cylinder station may not be the economic optimum to align solar panels and control orientaton, rotation speed and orbit, but instead a liquid oxygen/calcium metal energy cash could be used near the Moon and on the Moon's surface. See life down here on Earth uses ATP (high energy adenosine tri-phosphate) as the energy cash, and all processes within all lifeforms respect the resource limit of energy cash, and all processes either generate ATP with food or light energy from ADP (low energy adenosine di-phosphate) plus P, phosphoric acid, APP + P + energy ---> APPP, or APPP ----> APP + P + energy. So, similarly, near