Ladies and Gentlemen: Prepare to have your mind warped. Introducing the Alcubierre Warp drive: As I discussed in my post on the Einstein Field Equations (which is pinned to the top of this page at the time of this writing), General Relativity conceptualizes spacetime as a 4-dimensional manifold which can expand, contract, and curve, and in doing so served to reformulate the way in which we understand the effects of gravity. In short: spacetime tells matter how to move, and matter tells spacetime how to curve. General Relativity also provides a loophole around one of the key consequences of Einsteins Special Theory of Relativity from 10 years prior. Namely, that no object with mass can travel at the speed of light (in a vacuum) relative to some other local frame of reference. There are very good reasons for this, both theoretical and empirical, which I hope to elucidate in another post. It also has other more bizarre consequences such as time dilation, length contraction, mass-energy equivalence (i.e. E= mc^2) and so-called relativistic mass, whereby the inertia of an object increases as it approaches the speed of light such that the amount of energy required (or Work) to get it to accelerate a little more gets larger and larger and asymptotically approaches infinity as limit of v --> c. For now, suffice it to say that relativity still does not permit any object to go faster than light relative to any other local reference frame, but that it doesnt forbid space itself from expanding and contracting in such a manner that would simulate Faster-Than-Light (FTL) travel for practical intents and purposes. In fact, if youve ever heard of inflationary cosmology, which was an amendment to the original Standard Big Bang model, Inflation Theory capitalizes on this loophole in its description of the period from a trillionth of a trillionth of a trillionth of a second after after the initial Big Bang until about 10^-32 or 10^-33 of a second after it. Inflation theory is a matter for another post though. More to the point, another area in which this is being exploited is the study of Warp Field Mechanics. In 2012, a NASA laboratory announced that theyd built an interferometer that they claim will detect the spatial distortions produced by the expanding and contracting spacetime of what is know as the Alcubierre metric. A description of their work is included in Warp Field Mechanics 101, a NASA paper by Harold Sonny White, (a pdf copy of which is available upon request in the comments section below). The simplistic explanation is that the ship stays put while induced distortions of spacetime cause the space to contract in front of the spaceship, and to expand behind it. The warp drive idea is based on a valid solution to Einstein Field Equations. The warp drive solutions come about from utilizing the Alcubierre metric (which is named after its discoverer). A snapshot of it (from Warp field mechanics 101) is depicted in the middle frame of the attached photo. NASA has been running simulations and doing experiments based on this idea. However, if youre thinking that this sounds more like science fiction than science, thats because currently it still is. There are catches to the idea, not least of which is the fact that solutions to Einsteins equations involving the Alcubierre metric correspond to negative energy densities (negative values in the Stress Energy Tensor). In other words, it presupposes the existence of exotic matter of negative mass-energy density in order for it to work, and we do not have any evidence of the existence of such a type of matter. That said, we do know that our current theory of matter, the Standard Model of Particle Physics, which is based on quantum field theory, is incomplete, because none of the elementary fermions and bosons can account for the astronomical observations attributed to dark matter, but its unclear whether currently hypothesized solutions to the DM problem (such as Supersymmetry theories aka SUSY theories) will pan out in particle accelerator experiments because those frameworks are incapable of predicting the masses of the super-partner particles they postulate, and none of them have been discovered yet experimentally. To add,insult to injury, AFAIK, no currently posited version of SUSY hypothesizes the existence of matter with negative mass energy-density. But the take home message is that warp drive theories are compatible with our best understanding of the nature of spacetime, but its also still a bit of a long shot. Understand that there is a difference between speculative science (based on theories that have already established themselves in other areas), versus pseudoscience, which denies or ignores existing established principles of science and/or produces no testable predictions, and/or is not self-correcting. - The Credible Hulk (2nd try, since the text came out hard to read on the previous graphic).
Posted on: Wed, 21 Jan 2015 03:29:34 +0000
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