The Alcubierre “Warp” Drive

The Alcubierre “Warp” Drive

21 Aug , 2011 by

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It’s always a welcome thing to learn that certain ideas that are common to science fiction have a basis in science fact. Cryogenic freezers, laser guns, robots, silicate implants… and let’s not forget the warp drive! Believe it or not, this concept – alternately known as FTL (Faster-Than-Light), Hyperspace, Warp drive, et al – actually has one foot in the world of real science. In physics, it is what is known as the Alcubierre Drive (or the Alcubierre Metric). On paper, it is a speculative, but apparently valid, solution of the Einstein field equations, specifically how space, time and energy interact. In this particular mathematical model of spacetime, there are features that are apparently reminiscent of the fictional “warp drive” or “hyperspace” from notable science fiction franchises, hence the association.

Since Einstein first proposed his field equations in the early 20th century, scientists have been operating under the strictures imposed by a relativistic universe. One of these strictures is the belief that the speed of light is unbreakable and hence, that there will never be such a thing as FTL space travel or exploration. Even though subsequent generations of scientists and engineers managed to break the sound barrier and defeat the pull of the Earth’s gravitational field, the speed of light appeared to be one barrier that was destined to hold. But then, in 1994, a Mexican physicist by the name of Miguel Alcubierre came along with proposed method for stretching the fabric of space-time in way which would, in theory, allow FTL travel to take pace.

In short, the method involves stretching the fabric of space in a wave which would in theory cause the space ahead of an object to contract while the space behind it would expand. An object inside this wave (let’s say, a spaceship) would then be able to ride this region, known as a “warp bubble” of flat space. Since the ship is not moving within this bubble, but is being carried along as the region itself moves, conventional relativistic effects such as time dilation would not apply, hence the rules of space time and relativity would cease to be of concern. One of the reasons for this is because this method would not rely on moving faster than light in the local sense, since a light beam within this bubble would still always move faster than the ship. It is only “faster than light” in the sense that the ship could reach its destination faster than a beam of light that was travelling outside the warp bubble.

However, there is are few problems with this theory. For one, there are no known methods to create such a warp bubble in a region of space that would not already contain one. Second, assuming there was a way to create such a bubble, there is not yet any known way of leaving once inside it. As a result, the Alcubierre drive (or metric) remains in the category of theory at this time. Mathematically, it can be represented by the following equation: ds2= – (α2 – β1β1) dt2 + 2β1 dx1 dt + γijdx1 dxj, where α is the lapse function that gives the interval of proper time between nearby hypersurfaces, βi is the shift vector that relates the spatial coordinate systems on different hypersurfaces and γij is a positive definite metric on each of the hypersurfaces.

We have written many articles about the Alcubierre “Warp” Drive for Universe Today. Here’s an article about the possibility of warp drives, and here’s an article about warp drives and cloaking devices.

If you’d like more info on the Alcubierre “Warp” Drive, check out an article from Wikipedia. Also, check out another article about the warp drive spaceship engine.

We’ve also recorded an entire episode of Astronomy Cast all about Light Echoes. Listen here, Episode 215: Light Echoes.

Sources:
http://en.wikipedia.org/wiki/Alcubierre_drive
http://en.wikipedia.org/wiki/Einstein_field_equations
http://en.wikipedia.org/wiki/Hypersurface
http://en.wikipedia.org/wiki/Faster-than-light

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