Monday, January 30, 2006
Metric Engineering and the Good Ship Further
The Good Ship Further, the starship in the Big Time Space Opera I'm researching, will have FTL and artificial gravity. A few months ago I complained about the difficulties I was having coming to terms with the level of handwaving necessary to get artificial gravity on an interstellar spaceship without having to work out the mathematical complexities of a rotating crew section acclerating at high speeds. This was something that honestly kept me up nights, and seemed to be a brick wall I kept bashing my head against.
And then, this last weekend, I ran headlong into a paradigm shift. I was researching the Zero-Point Field, which I'd already decided would be the basis for power generation on the Further. I'd recently decided, too, that instead of some sort of magic "underspace impellers" the starship would be propelled by something like a bias drive or pitch drive, both proposed by Marc Millis of the late, lamented Breakthrough Physics Propulsion Program. I'd read up a bit on Alcubierre's "warp drive," but couldn't work out how to integrate it.
Then I found the website of the Institute for Advance Studies in Austin. And, more specifically, their report Engineering the Zero-Point Field and Polarizable Vacuum for Interstellar Flight, originally presented in 2001 at the University of Sussex. This one document, probably the best single primer on the relationship between ZPF and gravity that I've found, really opened my eyes, and helped to cast a lot of the material I'd already gathered in a new light. I don't think I've come across this "polarizable vacuum" representation of general relativity before, but it's fascinating. The part which really rings my bell was first proposed by a Russian physicist, Andrei Sakharov, in the late sixties. He proposed that "gravitation is not a fundamental interaction at all, but rather an induced effect brought about by changes in the quantum-fluctuation energy of the vacuum when matter is present."
Cool, huh? Well, I had to read that through a few times before it made it past my forehead. This idea is dependent on a completely different conception of space than that I've been taught. Put as simply as possible (and lensed through my own meager layman's understanding) it states that spacetime isn't curved, as has been the consensus since Einstein, but flat. And that the characteristics of flat space are modulated and modified by the presence of matter.
If you factor in something like Alcubierre's warp drive, which avoids relativistic effects by keeping the real acceleration of the contents of the warp "bubble" zero, then this gets really interesting. The creation of an Alcubierre warp bubble requires massive amounts of negative energy, but given that one of the characteristics of the Zero Point Field is negative energy, it seems like some sort of love connnection should be possible here.
While the paper proposes metric engineering to decouple gravity and inertia, it doesn't talk about generating gravity, but it seems to me if you can do the one, the other shouldn't be out of bounds. Which means that this gives me both FTL drive as well as artificial gravity, all from the same source, with a minimum of handwaving.
Now, I'm considering all of the wacky thing you could do with the ability to generate gravity. A rational basis for a "tractor beam"?
And then, this last weekend, I ran headlong into a paradigm shift. I was researching the Zero-Point Field, which I'd already decided would be the basis for power generation on the Further. I'd recently decided, too, that instead of some sort of magic "underspace impellers" the starship would be propelled by something like a bias drive or pitch drive, both proposed by Marc Millis of the late, lamented Breakthrough Physics Propulsion Program. I'd read up a bit on Alcubierre's "warp drive," but couldn't work out how to integrate it.
Then I found the website of the Institute for Advance Studies in Austin. And, more specifically, their report Engineering the Zero-Point Field and Polarizable Vacuum for Interstellar Flight, originally presented in 2001 at the University of Sussex. This one document, probably the best single primer on the relationship between ZPF and gravity that I've found, really opened my eyes, and helped to cast a lot of the material I'd already gathered in a new light. I don't think I've come across this "polarizable vacuum" representation of general relativity before, but it's fascinating. The part which really rings my bell was first proposed by a Russian physicist, Andrei Sakharov, in the late sixties. He proposed that "gravitation is not a fundamental interaction at all, but rather an induced effect brought about by changes in the quantum-fluctuation energy of the vacuum when matter is present."
Cool, huh? Well, I had to read that through a few times before it made it past my forehead. This idea is dependent on a completely different conception of space than that I've been taught. Put as simply as possible (and lensed through my own meager layman's understanding) it states that spacetime isn't curved, as has been the consensus since Einstein, but flat. And that the characteristics of flat space are modulated and modified by the presence of matter.
"In brief, Maxwell's equations in curved space are treated in the isomorphism of a polarizable medium of variable refractive index in flat space; the bending of a light ray near a massive body is modeled as due to an induced spatial variation in the refractive index of the vacuum near the body; the reduction in the velocity of light in a gravitational potential is represented by an effective increase in the refractive index of the vacuum, and so forth. "So this isn't just a question of gravity, but everything. The speed of light, "effective" mass, clock speeds, energy states, and "rulers"--all are no longer fundamental qualities, but secondary characteristics of the quantum vacuum. And if you were able to jigger the "variable vacuum dielectric constant" (how's that for a mouthful?), you could actually change those metrics. Reduce that constant, and you increase the local speed of light, decrease effective mass, speed clocks and expand rulers. How is that useful? Well, if you increase the speed of light, you get accelerate to arbitrarily fast speeds without violating the restrictions against acclerating past the speed of light. (Which, in retrospect, is the solution devised by the creators of Futurama!)
If you factor in something like Alcubierre's warp drive, which avoids relativistic effects by keeping the real acceleration of the contents of the warp "bubble" zero, then this gets really interesting. The creation of an Alcubierre warp bubble requires massive amounts of negative energy, but given that one of the characteristics of the Zero Point Field is negative energy, it seems like some sort of love connnection should be possible here.
While the paper proposes metric engineering to decouple gravity and inertia, it doesn't talk about generating gravity, but it seems to me if you can do the one, the other shouldn't be out of bounds. Which means that this gives me both FTL drive as well as artificial gravity, all from the same source, with a minimum of handwaving.
Now, I'm considering all of the wacky thing you could do with the ability to generate gravity. A rational basis for a "tractor beam"?
# posted by Chris Roberson @
9:33 AM
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Well, you have all the Ender's Game training applications. You have pleasure applications (there's a common idea that people would sleep really well in low gravity, among other things). You have medical applications (low-gee makes it much easier on patients with major injuries where just the weight of the body pressing on the injured area can be very problematic, and of course there's Lazarus Long's famous birth-via-gravity-spike). You have exercise and performance and sports applications up the wazoo. You could probably do some fascinating sculptures with materials that behave differently in different gravity situations, particularly liquids and dusts. There might be hydroponics applications. Would it affect pressurized areas?
How specific can you get? Can you have a high-gravity spot in a room that automatically "catches" anything you throw at it, like dirty clothes?
(Hi, I'm a fellow writer who wandered past and was intrigued. Nice to "meet" you!)
How specific can you get? Can you have a high-gravity spot in a room that automatically "catches" anything you throw at it, like dirty clothes?
(Hi, I'm a fellow writer who wandered past and was intrigued. Nice to "meet" you!)
My pet peeve with gravity control is that, unless you impose a lot of limitations on it, it lets you violate the conservation of energy, which I personally think is a bad idea for a fictional universe.
("The conservation of energy: it's not just the law, it's a good idea.")
("The conservation of energy: it's not just the law, it's a good idea.")
Alas, I'm going to feel really dumb with the great commentary and other comments (I'm so glad you found such an awesome way to work this!), but my comment is just...
That's a really cool name for a spaceship. :-)
That's a really cool name for a spaceship. :-)
Ted, that's something I've been worrying about, too. Not only because it's bad science, but because it leads too easily to bad storytelling. There needs to be a balance, even with "magic" handwaving technology, or you end up in a situtation where anything and everything is possible, and there aren't any interesting obstacles for the characters to overcome. This is something that the Star Trek writers seemed to have realized at some point, as they started imposing all sorts of restrictions (no transporting at warp speed, no weapons fire when cloaked, etc), without which things would have gotten pretty ridiculous (or, arguably, even more ridiculous).
The problem I've run into with the conservation of energy and the ZPF is that I'm having trouble groking what sorts of theoretical limits there are to the energetic potential of the ZPF. I've read some interesting papers that suggest that there might be an upper limit to how much zero-point energy could be extracted, not just locally but universally, but if someone has proposed math to back that up, I've either not seen it or it's beyond me (or both).
The problem I've run into with the conservation of energy and the ZPF is that I'm having trouble groking what sorts of theoretical limits there are to the energetic potential of the ZPF. I've read some interesting papers that suggest that there might be an upper limit to how much zero-point energy could be extracted, not just locally but universally, but if someone has proposed math to back that up, I've either not seen it or it's beyond me (or both).
Thanks, Deanna. A ship of exploration, Further originally had any number of different names, but they all ended up sounding too much like names used in different stories. In fact, at one point it was called Endeavour, after James Cook's ship, until I realized that endeavor is a synonym for "enterprise." Eventually a light dawned, and I realized I could draw inspiration from explorers of a different sort. So yes, there's something of Ken Keseys's "Furthur" in there. I don't think the crew will be wearing red-and-white striped jerseys, but at this point anything is possible.
Well, one potential problem with Zero Point energy is, if you're extracting usable energy from the vacuum, then you are necessarily dropping at least some fragment of spacetime down to a lower fundamental energy level... and how can you tell that it won't turn into a runaway reaction that spreads across space-time, dropping the universe as a whole to lower quantum energy level and releasing the tapped energy (enough to incinerate suns and galaxies) at the same time. Its sort of the ultimate exothermic reaction, except it's spatiotemporal rather than chemical in nature...
Very true, Scott (and I can't help but remember the guys on the Manhattan Project, who just weren't quite sure whether their first fission explosion wouldn't ignite the Earth's entire atmosphere in a runaway chain reaction... must have led to some sleepless nights, I wouldn't doubt). For the purposes of fiction, I may just have to assume that they didn't accidentally incinerate the entire Milky Way the first time they fired up the ZPF drive!
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