SpaceTime Engineering
But this was supposed to be a conservative implementation, utilizing
nothing more exotic than directed ultrarelativistic neutron stars.
Mitch Porter
This section deals with technology and science which uses the properties
of ####spacetime
in novel ways, or actually changes the properties (like wormholes
and basement universes).
These technologies are naturally very speculative at present, but the
scientific results below give an inkling of what may be possible.
Sections
FTL
Time Travel
Wormholes
Basement Universes
Other Sites
Books
See Also
Artificial gravity. A short description of
the torus method of Robert Forward of creating (a rather weak) gravity
field.
Cosmological Waveguides
for gravitational waves by G. Bimonte, S. Capozziello, V. Man'ko,
G. Marmo. Apparently gravitational waves can be led along waveguides of
dust, which might be useful in gravity manipulation.
The gravitational wave
rocket by W. B. Bonnor and M. S. Piper. In principle it ought to be
possible to move a rocket using gravitational waves.
FTL  Faster Than Light Travel
Travelling faster than light is an old dream, complicated due to relativity
and causality (FTL travel can cause causal loops in relativity). One way
of achiving extreme speeds in general relativity is to employ suitable warps
of spacetime, but the principal difficulties are severe. Another kind of
solution is wormholes.
The Warp Drive: HyperFast
Travel Within General Relativity by Miguel
Alcubierre (Class. Quantum Grav. 11 (1994), L73L77). Demonstrates
that by manipulating spacetime locally, a spaceship can move faster than
light as measured by the rest of the universe.
Hyperfast interstellar
travel in general relativity by S. V. Krasnikov. A paper that demonstrates
some limitations on FTL travel.
Quantum effects in the
Alcubierre warp drive spacetime by William A. Hiscock. Quantum effects
seems to prevent the use of the Alcubierre drive due to divergence of
the stressenergy tensor as lightspeed is approached.
The unphysical nature
of "Warp Drive" by Michael J. Pfenning and L.H. Ford. Another major
problem with the Alcubierre drive.
Superluminal
travel requires negative energies by Ken D. Olum. Superluminal travel
violates the weak energy condition (like most other stuff on this page).
Faster Than Light ?
by J. E. Maiorino and W. A. Rodrigues Jr. Discusses some electromagnetic
field configurations that appear to move faster than light, and how they
relate to the principle of relativity.
A
`warp drive' with more reasonable total energy requirements by Chris
Van Den Broeck A way of making the Alcubierre warp more "physical"
by exploiting a movable basement universe. He has another paper, On
the (im)possibility of warp bubbles, that discusses some of the objections.
Warp
factor one (Robert Matthews, New Scientist 12 June 1999). Popular
explanation of Chris Van Den Broecks trick to enable lowenergy warp spacetimes.
Time Travel
Time travel may appear even more outrageous than FTL, but both phenomena
are closely linked to each other. Causal loops (Closed Timelike Curves,
CTCs) exist in some solutions to general relativity. The question is whether
they can occur in physically relevant spacetimes and how paradoxes are avoided.
Time
Travel for Beginners by John Gribbin.
Time machines and the
Principle of SelfConsistency as a consequence of the Principle of Stationary
Action (II): the Cauchy problem for a selfinteracting relativistic particle.
Quantum effects and the principle of minimal action may lead to a 'principle
of selfconsistency' ruling out time paradoxes.
Wormholes
Wormholes are shortcuts through spacetime, connecting two distant locations
through a short "tunnel". They can exist in general relativity,
but the main issue is whether they are traversable and possible to create.
Traversable
Wormholes: Some Implications by Michael Clive Price. A very good introduction
to the possibilities of wormholes.
Wormhole
Warfare by Robin Hanson. A comment to the above text about the military
implications of wormholes.
Wormholes
in "The Alternate View" columns of John G. Cramer (Analog).
Technical Papers
Inflating Lorenzian Wormholes
by Thomas A. Roman. A technical paper about the possibility of using inflation
to turn a quantum wormhole macroscopic.
Can wormholes exist?
by V.Khatsymovsky. Technical paper about the renormalized vacuum expectation
values of electromagnetic stressenergy tensor in wormhole spacetimes.
Apparently they can be stable.
Dynamic wormholes
and energy conditions by Wang, A ; Letelier, P S. Non static wormholes
can obey the weak and dominant energy conditions.
Bubbles and
wormholes: analytic models, by Wang, A ; Letelier, P S. Discusses
spacetime bubbles and how wormholes could link them.
Towards possibility of
selfmaintained vacuum traversible wormhole by V. Khatsymovsky
Traversable wormholes:
the Roman ring by Matt Visser. Apparently chronology protection can
be fooled by more complex arrangements of wormholes.
Rotating
traversable wormholes by Edward Teo.
Toward
a Traversable Wormhole by S. V. Krasnikov
Basement Universes
According to some theories, it is possible to spawn new universes (i.e.
independent volumes of spacetime) through various means. This could be
used for a variety of things, such as computation or escape from a unsuitable
spacetime.
Text of
`Baby Universes, Children of Blackholes' by S.W. Hawking
Baby Universes (This Week's
Finds in Mathematical Physics (Week 31)) by John Baez. About the possibilities
of "baby universes", and how they might be formed.
Possible Implications
of the Quantum Theory of Gravity, An Introduction to the MedusoAnthropic
Principle by Louis Crane. Nontechnical paper about how the activities
of technological civilizations could influence the evolution of baby universes.
The fate of black hole
singularities and the parameters of the standard models of particle physics
and cosmology by Lee Smolin. If baby universes can develop and the
parameters of the standard model can be modified in subsequent universes,
then evolution could act on entire universes.
Design
for an infinitely fast computer by Alexander
Chislenko. Perhaps not entirely practical, but definitely shows that
very innovative designs are possible.
Other Sites
Books
C W Misner, K S Throne, and J A Wheeler, Gravitation, (Freeman)
UL QC 178.M57. The classic textbook.
Robert Forward, Indistinguishable from Magic, Pocket Books; ISBN:
0671876864 1995
See also
Relevant newsgroups: rec.arts.sf.science,
sci.physics
