The physics of warp travel

To quote Douglas Adams inHitchhiker’s Guide to the Galaxy, space is big. The nearest celestial object to Earth is the moon, and that is 383,400 KM away from us. It takes light just over 1 second to travel from the lunar surface to the Earth’s surface. When you look up at the sky and see the sun, you’re not seeing it as it is at that moment in time, but as it was just over 8 minutes ago, it takes light that long to travel the distance between the solar surface and ours. And light from the nearest stars, other than the sun? That takes a little over four years to reach us. Any ship travelling at the best speeds possible with current technology would take about 10,000 years to reach such a destination. Even travelling at half the speed of light, it would still take a vessel 8 years to complete the journey. If Earth and Mars were the heads of pins, modelled to proportional scale, and the pinhead of Mars were one centimetre away from the pinhead of Earth, then the pinhead representing Alpha Centauri would be 20 KM away. If humanity is ever to explore beyond the solar system’s boundaries we will need to invent a radically different method of ship propulsion than we know and use today.

This is where warp drive comes in.

In his 1994 paper entitled The warp drive: hyperfast travel within general relativity (PDF) scientist Miguel Alcubierre outlines how it might be possible to create an area of expanded space behind a vessel, and contracted space in front of it, so the ship itself “surfs” through the universe on a “wave” of distorted space-time. The effect is that the ship, and anyone on it, can travel at faster-than-light (FTL) speeds with none of the effects that General Relativity would impose, such as local increases in mass or time dilation. This is because the vessel and everything in it are enclosed in a “bubble” and so are entirely stationary relative to their own local space; from the point of view of an observer from outside the “bubble” the ship appears to travel at speeds greater than light.

The image below shows how such a vessel might distort the fabric of space-time to create and ride its “warp bubble”.

There are problems, of course – we’re never going to be able to travel faster than light without issues. The main one is the energy and type of matter required to create this “warp”. As with wormholes, the warp drive relies on the use of so-called “exotic matter” – matter with unusual properties that allows for the localised distortion of space. The thickness of the warp would be a few hundred Planck Lengths – around the smallest distance possible. Controlling something so small would require an enormous amount of energy. In their paper The Unphysical Nature of “Warp Drive” (PDF) scientists Michael Pfenning and L. H. Ford calculate that the negative energy required to propel a 200 metre long craft to 10 times the speed of light would require more than one billion times the energy-mass of the whole visible universe.

You’d think that would be it, then. It might be possible, but the amount of energy required is so daunting as to make it impossible. Well, its not.

Physicist Chris Van Den Broeck write in his paper A Warp Drive With More Reasonable Total Energy Requirements (PDF) that by modifying the geometry of the warp and the way it oscillates, you can bring down the total energy requirements. In a presentation on the subject of warp drives, NASA’s Dr Harold White explained that these tweaks meant that a hypothetical warp drive could be powered by an energy-mass of around 1600 pounds – about the same weight as the Voyager spacecraft. In order to prove the theories regarding the creations of warp fields, a test facility has been developed at NASA’s Johnson Space Centre where the White-Juday Warp Field Interferometer experiment is being run.

So, since Star Trek first popularised the idea of a warp drive in 1966 we have gone from the idea being something that was impossible and only happens in sci-fi, through possible but impractical due to its energy requirements to possible and being tested in a lab. And all of this in only 50 years. Where will we be in another 50 years? Well, according to Dr White, if the experiments prove positive, the next stage would be a craft leaving Earth’s orbit with conventional engines, stopping (relative to Earth) and activating its warp drive. It would then fly to a point near its destination, deactivate its warp drive and complete the last stage of its journey on conventional engines. Calculations predict that travel time from Earth to Alpha Centauri could be cut down to a mere few weeks.

Dr White is hoping the lab experiments into the generation of a warp field will be something akin to the “Chicago Pile” experiments: back in 1942, humanity activated the first ever nuclear reactor. It generated a pitiful half a watt of power – not enough to power a light bulb. Just under a year later we activated at 4MW reactor – producing enough power to meet the needs of a small town – the existence of proof is a very important first step.

Anyone interested in learning more about how warp drive might work is encouraged to read the scientific papers linked to above, or take a read through Dr White’s Warp Field Mechanics 101 (PDF) – I should warn you, this is deep physics and not for the faint-hearted!

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