Whereby a spacecraft travels faster than light (FTL)
by John G. Hartnett
Gene Roddenberry’s classic sci-fi drama, Star Trek, made famous the warp drive, a theoretical concept whereby a spacecraft travels Faster Than Light (FTL).
A ‘trekky’ enthusiast once told me that the warp speeds described on the television shows and in the movies may be calculated as follows. Warp factor w, from the original Star Trek series, means that the spacecraft travels at w³ times the canonical speed of light (c ≅ 300,000 km/s or 186,000 miles/s).3 Therefore warp factor w = 7 means the spacecraft travels at 7 = 343 c. It would be unusual to hear that the starship the USS Enterprise (see Figure 1) had exceeded warp factor 9, which is about 729 times the speed of light.
To travel even around the local neighbourhood of our galaxy warp factor 9 (from the original TV series) just won’t do it. The nearest star to our solar system is about four light-years away. So travelling at warp 9, you would take two days to get there. Not too bad. But what about going to other star systems?
To travel 50 light-years, which is a very small distance in the galaxy and which includes very few stars—only 64 sun-like stars—would take you 25 days at this speed. Within a distance of 100 light-years from Earth there are known to be only 512 stars of the same spectral class as our sun and very few of those might be candidates for a solar system that could potentially support life. So it would be much better to be able to travel 100 light-years quite quickly; but that would take you 50 days. However in the TV shows they often arrive in just a matter of hours.
Years later, the next TV series—Star Trek: the Next Generation—solved this problem by introducing a new formula that increased the warp speed in a highly non-linear fashion, such that a warp factor of 10 meant infinite speed across the galaxy. Thus distances were no longer a roadblock to get around the universe in the 40 minutes or less available in a TV episode. For example, warp factor w = 9.9999 is equal to nearly 200,000 c. At that speed you could hypothetically travel right across the galaxy in only six months.
Alcubierre Warp Drive
But that is all science-fiction. What about a real warp drive? In 1994, a Mexican physicist by the name of Miguel Alcubierre came up with a proposal for stretching the fabric of space-time in a way which would, theoretically, permit FTL travel.
Alcubierre found a theoretical solution of Einstein’s field equations producing what has been called Alcubierre Warp Drive. Needless to say it is a highly speculative mathematical model, which specifies how space, time and energy interact.
To put it simply, this method of space travel involves stretching the fabric of space-time 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 (i.e. a spaceship) would then be able to ride this region, known as a “warp bubble” of flat space.What is the Alcubierre “Warp” Drive?, universetoday.com
The spacecraft hypothetically generates the warp bubble in its bow wake and collapses it behind the craft as it travels through space-time. See Figure 2. The speed of light within the bubble remains the same speed of light, c. The spacecraft undergoes no local acceleration—no huge g-forces are experienced by the craft. Thus Captain James T. Kirk, or anyone else on board, would not spill his/her coffee even as they go to warp 9.9999.
But the idea of warp drive presents a few problems…
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image credit: Artwork of TV’s first “Star Trek” crew