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There’s an exciting news item  floating about describing NASA’s Theoretical Propulsion Unit and other research centers that describes a possible warp drive. Rimjob describes it here. Centauri Dreams has more here

This isn’t the first possible apparent-faster than light drive that’s popped up in theoretical physics in recent years. I do try to keep up with these, as I have been working on a novel and its background universe for over a decade now and have been looking for possible way to make FTL work (I found one, but I'm not sharing!).  As one hard-science fiction site says,

Causality, Relativity, FTL travel: chose any two” and if you’re going to choose all three, make sure you have limits that are logical and consistent. Nerds will still try to break it. It's what we do.  

While I’m not a physicist (the last time I had physics was in 1999!), I thought I’d write a diary about what I know about the two ideas about apparent faster than light travel that I know a bit about, and hope others could share what they know in the comments.  No, this isn’t a political diary as I don’t write those. This is just a hopefully fun science diary. Make the jump if you want to continue.

The Alcuibierre Drive

In 1994, physicist Miguel Alcubierre wrote about a metric for a spacedrive:

"It is shown how, within the framework of general relativity and without the introduction of wormholes, it is possible to modify a spacetime in a way that allows a spaceship to travel with an arbitrarily large speed. By a purely local expansion of spacetime behind the spaceship and an opposite contraction in front of it, motion faster than the speed of light as seen by observers outside the disturbed region is possible. The resulting distortion is reminiscent of the `warp drive' of science fiction. However, just as happens with wormholes, exotic matter will be needed in order to generate a distortion of spacetime like the one discussed here.”
This is basically the drive NASA is researching. In English, the spaceship would somehow project a bubble that would expand spacetime behind the ship. In front of the ship, spacetime would contract. The ship itself would not be moving faster than light (from the vantage point of a person within the ship) but outside of the bubble, the distortion would appear to move faster than light, thus the “apparent” FTL that special relativity does allow for.

It also requires “exotic matter,” which as of yet, doesn’t exist. Handwavium, unobtainium, whatever you want call it, it at present is not physically real. We’ll use unobtainium for now, because it’s a fun and apt word.

Critiques of the Alcubierre Drive (which the creator has stated was basically just a fun thought experiment, but I love that he watched Star Trek and used his knowledge to try to figure out how it could possibly work) have stated the drive would require vast amounts of unobtainium, in the order of several solar masses or more, perhaps more than the available energy of the universe   . In addition, you might not be able to communicate to turn the bubble on or off. The edges of the bubble would have immense tidal forces due to the curvature of spacetime---don’t turn your bubble on within a star system!---but you should be okay in your spaceship within the center of the bubble. Or not. It might get so hot and so radioactive inside the bubble that you’ll cook like crispy, glowing bacon and die horribly and painfully. Yum.

Later study indicates that the amount of unobtainium needed would be much smaller—perhaps only a few kilograms.

The news that has everyone excited this week comes from NASA . NASA has long had a Theoretical Propulsion Unit that has been inactive and active at different times through the space agency’s history. It appears they’re getting ready to do an actual experiment [pdf]: create a tiny, tiny Alcubierre bubble.

This is exciting. We’ll see what happens. In their own words:

Those equations are tested using an instrument called the White-Juday Warp Field Interferometer. At JSC, Eagleworks has initiated an interferometer test bed that will try to generate and detect a microscopic instance of a little warp bubble. Although this is just a tiny instance of the phenomena, it will be existence proof for the idea of perturbing space time—a “Chicago pile” moment, as it were. Recall that December of 1942 saw the first demonstration of a controlled nuclear reaction that generated a whopping half watt. This existence proof was followed by the activation of a ~ four megawatt reactor in November of 1943. Existence proof for the practical application of a scientific idea can be a tipping point for technology development.
Way exciting.
(The Alcubierre Drive, incidentally, shows up in very little science-fiction but is gaining ground in the fairly hard sci-fi genre, although the notes for the very first Star Trek movie envision a drive that sounds very much like the Alcubierre Drive. And for what it’s worth, in the Star Trek Universe, Zephram Cochrane gets born next year.)

The Heim Drive

I can’t even begin to explain Heim theory. Apparently no one really can. The theory, created by a reclusive, disabled and brilliant German physicist named Burkhard Heim  is an attempt to develop a theory of everything, using six to twelve dimensions.

In 2006, some excitement was made over the possibility that Heim theory  predicts hyperspace. Three hours to Mars? 80 days to Tau Ceti? (I would link to the New Scientist articles that discuss this but alas, they’re behind a paywall now, but here’s one of the papers published about “hyperspace.” Very technical PDF.)

I’m going to attempt to explain how this would work as I understand it. The engine, which is comprised of a huge rotating ring placed above a superconducting coil, creates an intense magnetic field. This field would be able to reduce the pull of the Earth until it floats free into space (flying cars? Hovercraft?  Vertical-takeoff aircraft? Very many more applications than just a hyperdrive here). And if the ring spins even faster, somehow your spaceship attached to the ring can enter a hyperspacial reality. Smarter people in the comments thread on these Centauri Dreams  posts say much, much more. This is one of the few times I’ll actually suggest reading the comments.

Is it Possible?

Relativity states you can’t violate causality, and a FTL drive would do just that. Special relativitystates it’d be a type of time-travel. When you look up into the night sky, you’re essentially looking backwards in time. That light from the stars is light that took dozens and hundreds of years to reach us. This site explains it better than any site I’ve found on the internet and I highly recommend it. Even the comments are tolerable.

Both drives, though, appear to not violate causality per se.

I don’t know if either way is possible, but I think it’s a worthy area of study. Kudos to those in theoretical physics who do so. This is what science is all about.

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