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Warp Drive and the Kardashev Scale: Our Competence of Travelling Faster than Light
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The prospects for a realistic engineered warp drive are currently within
the realms of scientific speculation. The pioneering paper by Alcubierre
has started a new field of research and in a period of a little over a
decade has seen some encouraging developments. This has led to a better
definition of the problem using the mathematical tools of general
relativity and quantum field theory. Many publications now exist which
have identified many technical problems and explored realisable
solutions. Some of these ideas may one day make warp drive a genuine
contender for breaking the interstellar distance barrier - the biggest
obstacle towards the potential interaction of interstellar
civilizations. This paper will review the current status of the warp
drive since the seminal paper and discuss the tremendous theoretical
advances that have been made. The problem definition will be considered
in the context of the NASA Horizon mission methodology.
We will apply the quantum-inequality-type restrictions to Alcubierre's warp drive metric on a scale in which a local region of spacetime can be considered `flat'. These are inequalities that restrict the magnitude and extent of the negative energy which is needed to form the warp drive metric. From this we are able to place limits on the parameters of the `warp bubble'. It will be shown that the bubble wall thickness is on the order of only a few hundred Planck lengths. Then we will show that the total integrated energy density needed to maintain the warp metric with such thin walls is physically unattainable.
It is shown how, within the framework of general relativity and without the introduction of wormholes, it is possible to modify a spacetime in a way that allows a spaceship to travel with an arbitrarily large speed. By a purely local expansion of spacetime behind the spaceship and an opposite contraction in front of it, motion faster than the speed of light as seen by observers outside the disturbed region is possible. The resulting distortion is reminiscent of the ``warp drive'' of science fiction. However, just as it happens with wormholes, exotic matter will be needed in order to generate a distortion of spacetime like the one discussed here. Comment: 10 pages, 1 figure. Not previously available in gr-qc
The radical limit of post-anthropocentric creativity is a mode of completely nonhuman creative endeavour. Yet, the anthropocentrism prevails and conceptions of radically different civilisations and cultures are defined by current human thought that shapes and limits the understanding of what a genuinely alternative cultural production might entail. This article uses the Kardashev scale of civilisations, classified according to energy consumption at the planetary, stellar and galactic scales to consider culture beyond the current limits of an inherently anthropocentric perspective. In considering microdimensional, informational and universal extensions of Kardashev's scale, critical reflections on the anthropocentric limits of cultural epistemology create an opportunity to posit a universal framework of creativity.
This paper will begin with a short review of the Alcubierre warp drive metric and describes how the phenomenon might work based on the original paper. The canonical form of the metric was developed and published in [6] which provided key insight into the field potential and boost for the field which remedied a critical paradox in the original Alcubierre concept of operations. A modified concept of operations based on the canonical form of the metric that remedies the paradox is presented and discussed. The idea of a warp drive in higher dimensional space-time (manifold) will then be briefly considered by comparing the null-like geodesies of the Alcubierre metric to the Chung-Freese metric to illustrate the mathematical role of hyperspace coordinates. The net effect of using a warp drive "technology" coupled with conventional propulsion systems on an exploration mission will be discussed using the nomenclature of early mission planning. Finally, an overview of the warp field interferometer test bed being implemented in the Advanced Propulsion Physics Laboratory: Eagleworks (APPL:E) at the Johnson Space Center will be detailed. While warp field mechanics has not had a "Chicago Pile" moment, the tools necessary to detect a modest instance of the phenomenon are near at hand.
In this Letter we consider a warp drive spacetime resulting from that suggested by Alcubierre when the spaceship can only travel faster than light. Restricting to the two dimensions that retains most of the physics, we derive the thermodynamic properties of the warp drive and show that the temperature of the spaceship rises up as its apparent velocity increases. We also find that the warp drive spacetime can be exhibited in a manifestly cosmological form. (c) 2007 Elsevier B.V. All rights reserved.
The construction of wormholes and warp drive would require a very unusual form of energy. Unfortunately, the same laws of physics that allow the existence of this "negative energy" also appear to limit its behavior
In this paper, we briefly review the basic theory of the Alcubierre drive, known as the Warp Drive Concept, and its subse- quent improvements. By using the Arnowitt-Deser-Misner formalism we then re-formulate an extended extrinsic curvature which corre- sponds to the extra curvature of the Extended General Relativity (EGR). With this preparation, we are able to generalize the Alcu- bierre metric wherein the space-like hypersurfaces are Riemannian, and the characteristic Alcubierre function is associated with the EGR geometry. This results in a reduced energy density tensor, whose form displays a potential ability to avoid the weak energy condition.
It has been suggested that an advanced civilization might have the technology to warp spacetime so that closed timelike curves would appear, allowing travel into the past. This paper examines this possibility in the case that the causality violations appear in a finite region of spacetime without curvature singularities. There will be a Cauchy horizon that is compactly generated and that in general contains one or more closed null geodesics which will be incomplete. One can define geometrical quantities that measure the Lorentz boost and area increase on going round these closed null geodesics. If the causality violation developed from a noncompact initial surface, the averaged weak energy condition must be violated on the Cauchy horizon. This shows that one cannot create closed timelike curves with finite lengths of cosmic string. Even if violations of the weak energy condition are allowed by quantum theory, the expectation value of the energy-momentum tensor would get very large if timelike curves become almost closed. It seems the back reaction would prevent closed timelike curves from appearing. These results strongly support the chronology protection conjecture: The laws of physics do not allow the appearance of closed timelike curves.
It will be shown that while horizons do not exist for warp drive spacetimes
traveling at subluminal velocities horizons begin to develop when a warp drive
spacetime reaches luminal velocities. However it will be shown that the control
region of a warp drive ship lie within the portion of the warped region that is
still causally connected to the ship even at superluminal velocities, therefore
allowing a ship to slow to subluminal velocities. Further it is shown that the
warped regions which are causally disconnected from a warp ship have no
correlation to the ship velocity.