By Kevin Roeten:
Warp Drive Almost Here
Theoretically, an Alcubierre Warp Drive moves space-time in a wave, and causes space ahead of a moving spacecraft to contract and the space behind it to expand. The ship can ride the wave to accelerate to high speeds and time travel. Star Trek vernacular, acceleration to “Warp 1” would simply require a wave of space-time, and “Warp 10” would require push by space-time at least 100x faster.
In 1994, the Mexican physicist Miguel Alcubierre proposed stretching space in a wave which would cause the fabric of space ahead of a spacecraft to contract, and the space behind it to expand. This is a Lorentzian manifold, and per relativity, exhibits abilities of the warp drive from Star Trek. A warp bubble would appear in previously flat space-time and move off at effectively superluminal (faster-than-light) speed. Inhabitants of the bubble feel no inertial effects. The object(s) within the bubble are not moving (locally) faster than light, instead, the space around them shifts so the object arrives at its destination faster than light would in normal space.
Because of the contraction of space in front of it, the ship would reach its destination faster than a light beam restricted to travelling outside the warp-bubble. Thus, the Alcubierre drive does not contradict the conventional claim relativity forbids a slower-than-light object to accelerate to faster-than-light speeds.
Does Negative Energy Really Exist?
In this huge ‘differential’ equation, the energy density is actually negative. Therefore, one would need exotic matter to travel faster than the speed of light. The Casimir effect and the accelerating universe both lend support to the proposed existence of such matter. Some scientists have argued that within general relativity, it is impossible to construct a warp drive in the absence of exotic matter. It is generally believed a consistent theory of quantum gravity will resolve issues for any Alcubierre warp drive dificulties.
Thus, as the energy density is negative, one needs exotic matter to travel faster than the speed of light. However, existence of exotic matter does possibly exist. The Casimir effect and the accelerating universe both lending support to the existence of exotic this matter.
Special Space Time Geometry
The Alcubierre Warp Drive has special space-time geometry. As a result, time travel to the future is possible. It can accomplish matter and information transport at superluminal speeds. It is technically viable, and is possible without exotic materials. As mentioned, it’s the exotic materials that would propel a warp drive. Without any exotic materials, only subliminal, or slower-than-light speed is possible. Still, with subliminal speed from the Alcubierre Drive, it would still exceed present-day velocities by 100x.
In over Warp-1 superluminal speeds, a warp-bubble appears in previously flat space-time, and travels at superluminal speed. Astronauts in the warp-bubble would feel no inertial effects. Any object(s) within the warp bubble would not move (locally) faster than light. Rather the space around them shifts so the object(s) arrive at its destination faster than light would in normal space.
With Special Relativity, such as Lorentz contraction and time dilation, the Alcubierre metric has some very strange aspects. Specifically, Alcubierre has shown even when the ship is accelerating, it travels on a free-fall geodesic. In other words, a ship using the warp to accelerate and decelerate is always in free fall, and the crew would experience no ‘accelerational’ g-forces. The pilot inside the warp-bubble is actually disconnected with its walls, and cannot perform any action outside the warp-bubble.
Alcubierre published a remarkable paper in general relativity–the current “standard model” for space-time and gravitation. This paper describes a very unusual solution to Einstein’s equations of general relativity, called a “warp drive”, and “a modification of space-time in a way that allows a space ship to travel at an arbitrarily large speed”.
Possibility Of Tachyon Existence
In special relativity, the speed of light [c], is the absolute speed limit of the universe for any object having a real mass (i.e., everything but the semi-mythical tachyon). General relativity treats special relativity as a restricted sub-theory, applying locally to any region of space sufficiently small, neglecting its curvature. General relativity does not forbid faster-than-light travel or communication, but it does require special relativity restrictions. Put simply, light-speed is the local speed limit, but general relativity provides an end-run to this rule. One end-run is a wormhole [connecting two widely separated locations in space]. An object might take a few minutes to move with at low speed through the neck of a wormhole,. However, by transiting the wormhole the object could have traveled five light-years in a few minutes, producing a real speed of a million times the velocity of light.
Wormholes Fill The Pot
In summation, Special Relativity will not allow objects to move faster than light within space-time, but it is known space-time itself can be warped and distorted. Shockingly, wormholes do invite the old time travel paradox problems again. Special Relativity forbids objects to move faster than light within space-time, but it is unknown how fast space-time itself can move.
If one uses the “Inflationary Universe” perspective, for example, it is thought that space-time expanded faster than the speed of light during the early moments of the Big Bang. So if space-time can expand faster than the speed of light during the Big Bang, why not for our warp drive?
First, to create this effect, you’ll need a huge ring of negative energy wrapped around the ship. Physics still debates the presence of negative energy. Classical physics tends toward a “no,” while quantum physics leans to a “maybe, yes.” Second, one must now how to turn this effect on and off at will. And, it must be remembered this warp effect is a completely separate effect from the ship. Third, and most importantly, the assumptions is the whole “warp” would indeed move faster than the speed of light. We’re talking major unknowns in #3.
To muddle the pot, it has been shown is theoretically possible to create a continuously propulsive effect by the juxtaposition of negative and positive mass, and it won’t violate conservation of momentum or energy. For negative mass, does it exist, or is even theoretically allowed. Evidently one can search for negative mass in the context of searching for astronomical evidence of wormholes.
© Copyright by Kevin Roeten, 2015. All rights reserved.