Wednesday, July 23, 2008

Is there a plausible basis for faster-than-light travel? (Part I)

An inherent premise of the extraterrestrial hypothesis for UFOs, is that the vehicles or craft must possess FTL (‘faster than light’) speed capabilities. This stands to reason. If interstellar craft are constrained by the Einsteinian limit of 186,000 miles per second, then long interstellar voyages and colonization become highly problematical. Particularly, since the probability for star systems with planets that support intelligent life increases with distance.

Hence, if UFOs are truly the craft of extraterrestrial ‘visitors’- and not some hitherto unknown meteorological, optical or electrodynamic phenomenon- then they must have traveled to Earth at higher-than-c velocities. But how is this possible if special relativity forbids anything traveling faster than light?

In this article, I examine a number of hypothetical explanations that also have some basis in either mathematics or physics. Each of these incorporates or allows FTL in some kind of limit. While not proving that such mechanisms actually underlie UFO operation, I argue that they certainly lend credibility to the concept of FTL interstellar travel via artificial craft.

Before proceeding to informed speculations, let’s consider actual experimental verification. In a paper appearing in the journal Nature, in July 2000, physicists at the NEC Research Institute in Princeton, New Jersey. claimed to have broken the limit set by the speed of light. They achieved this by firing a laser pulse into a glass chamber filled with a cesium (Cs) atom vapor.

NEC’s Lijun Wang, in fact, insisted he’d created an experiment in which light speed was not merely exceeded by an added increment, but by a factor of three hundred! This meant that an almost identical light pulse exited the chamber and traveled about sixty feet before the main part of the laser pulse finished entering the chamber, Wang said.

Needless to say, this flouts well-known accepted precepts of causality. (Wherein causes are assumed to precede effects). Relativity purists may also be gratified to know that a number of physicists question the interpretation of the results.

Validity will therefore have to await a confirmation of the experimental results. In the meantime, let’s move on to consider other more speculative scenarios:

1. The Alcubierre Warp Drive

The concept of the FTL warp drive was probably first coherently developed by Miguel Alcubierre of The Department of Physics and Astronomy, University of Wales, in 2000. For this to work, he postulates a ‘local expansion of space-time’ behind a spacecraft, while at the same time there’s an opposite contraction of space-time in front of it. The resulting distortion is analogous to many ‘warp drives’ invoked in science fiction.

However, there is this important difference: in the Alcubierre warp drive travelers are never really moving faster than the speed of light, since technically they always remain “in their own light cones”. So, rather than an FTL displacement of their inertial reference frame (attached to the ship) itself, it is the expansion of space-time that creates the enormous speed of separation.

To obtain this, the appropriate metric must be found, e.g. to “push” the craft along a trajectory described by an arbitrary function of time x S (t). . For a 4D, Cartesian system, with displacement along the x-axis, Alcubierre provides:

alpha = 1

beta^ X = - v S (t) f (r_s (t))

beta ^y = b eta^z = 0

gamma_ ij = delta_ ij

In the preceding formalism, gamma_ ij denotes the 3-metric of hyper-surfaces with constant coordinate time t, a is the ‘lapse function’ (generally a = 1) giving the proper time interval between hyper-surfaces as determined by Eulerian observers[2], the beta_i (i= x, y, z) denotes the ‘shift vector’ relating spatial coordinate systems on different hyper-surfaces. The full metric (for a line element or interval) in this space-time is given by (cf. Alcubierre, 2000):

ds^2 = -dt^2 = g_alpha beta dx_alpha dx_beta = - (a^2 - beta_i beta_i) dt^2 + 2 beta_i dx_i dt + gamma_ ij dx_i dx_j

The primary proviso for the above, is that the 3-metric be ‘positive-definite’ for all values of t, so the space time is then globally ‘hyperbolic’. The key point is that for the conditions set out, there’ll be no causal curves, generating the sort of paradox described in the experiment on the laser pulse at NEC Research Institute. It’s important to bear in mind that proper time always applies to the coordinates of the starting and destination points, as well as to the craft. (Though the latter will be subject to time dilation during the initial and final stages of the trip – when moving through flat space-time). This means that only the time on the craft is affected, but that the home world of the travelers – say if at immense distance – would long since have changed by their return. A depiction of an Alcubierre –style ‘warp deformation’ is given at the link below

http://www.zamandayolculuk.com/cetinbal/warpDrivesx.htm


As described already, the cylindrical deformation represents the expansion of space-time behind the hypothetical craft (in hyperbolic space) while the reverse deformation or contraction lies in front of the craft. The tandem is what generates an acceleration leading to v > c in the ship’s reference frame.

NEXT: Variable Speed of Light and Variable Time

1-A ‘hyperbolic’ space-time is one in which the curvature has the value k = -1.


[2] That is, with 4-velocities normal to the given hyper-surface.

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