Can the Vacuum be Engineered for Spaceflight Applications?
Overview of Theory and Experiments
H.E. Puthoff, Ph.D.
This paper was originally presented at the NASA Breakthrough Propulsion
Physics Workshop
NASA Lewis Research Center, Cleveland, OH, August 12-14, 1997
ABSTRACT
Quantum theory predicts, and experiments verify, that empty space (the
vacuum) contains an enormous residual background energy known as zero-point
energy (ZPE). Originally thought to be of significance only for such
esoteric concerns as small perturbations to atomic emission processes,
it is now known to play a role in large-scale phenomena of interest
to technologists as well, such as the inhibition of spontaneous emission,
the generation of short-range attractive forces (e.g., the Casimir force),
and the possibility of accounting for sonoluminescence phenomena. ZPE
topics of interest for spaceflight applications range from fundamental
issues (where does inertia come from, can it be controlled?), through
laboratory attempts to extract useful energy from vacuum fluctuations
(can the ZPE be "mined" for practical use?), to scientifically-grounded
extrapolations concerning "engineering the vacuum" (is "warp-drive"
space propulsion a scientific possibility?). Recent advances in research
into the physics of the underlying ZPE indicate the possibility of potential
application in all these areas of interest.
INTRODUCTION
The concept "engineering the vacuum" was first introduced by Nobel
Laureate T. D. Lee (1988) in his book Particle Physics and Introduction
to Field Theory. As stated there: "The experimental method to alter
the properties of the vacuum may be called vacuum engineering... If
indeed we are able to alter the vacuum, then we may encounter some new
phenomena, totally unexpected." Recent experiments have indeed shown
this to be the case.
With regard to space propulsion, the question of engineering the vacuum
can be put succinctly: "Can empty space itself provide the solution?"
Surprisingly enough, there are hints that potential help may in fact
emerge quite literally out of the vacuum of so-called "empty space."
Quantum theory tells us that empty space is not truly empty, but rather
is the seat of myriad energetic quantum processes that could have profound
implications for future space travel. To understand these implications
it will serve us to review briefly the historical development of the
scientific view of what constitutes empty space.
At the time of the Greek philosophers, Democritus argued that empty
space was truly a void, otherwise there would not be room for the motion
of atoms. Aristotle, on the other hand, argued equally forcefully that
what appeared to be empty space was in fact a plenum (a background filled
with substance), for did not heat and light travel from place to place
as if carried by some kind of medium?
The argument went back and forth through the centuries until finally
codified by Maxwell's theory of the luminiferous ether, a plenum that
carried electromagnetic waves, including light, much as water carries
waves across its surface. Attempts to measure the properties of this
ether, or to measure the Earth's velocity through the ether (as in the
Michelson-Morley experiment), however, met with failure. With the rise
of special relativity, which did not require reference to such an underlying
substrate, Einstein in 1905 effectively banished the ether in favor
of the concept that empty space constitutes a true void. Ten years later,
however, Einstein's own development of the general theory of relativity
with its concept of curved space and distorted geometry forced him to
reverse his stand and opt for a richly- endowed plenum, under the new
label spacetime metric.
It was the advent of modern quantum theory, however, that established
the quantum vacuum, so-called empty space, as a very active place, with
particles arising and disappearing, a virtual plasma, and fields continuously
fluctuating about their zero baseline values. The energy associated
with such processes is called zero-point energy (ZPE), reflecting the
fact that such activity remains even at absolute zero.
THE VACUUM AS A POTENTIAL ENERGY SOURCE
At its most fundamental level, we now recognize that the quantum vacuum
is an enormous reservoir of untapped energy, with energy densities conservatively
estimated by Feynman and Hibbs (1965) to be on the order of nuclear
energy densities or greater. Therefore, the question is, can the ZPE
be "mined" for practical use? If so, it would constitute a virtually
ubiquitous energy supply, a veritable "Holy Grail" energy source for
space propulsion.
As utopian as such a possibility may seem, physicist Robert Forward
(1984) at Hughes Research Laboratories demonstrated proof-of-principle
in a paper "Extracting Electrical Energy from the Vacuum by Cohesion
of Charged Foliated Conductors." Forward's approach exploited a phenomenon
called the Casimir Effect, an attractive quantum force between
closely-spaced metal plates, named for its discoverer, H. G. B. Casimir
(1948) of Philips Laboratories in the Netherlands. The Casimir force,
recently measured with high accuracy by S. K. Lamoreaux (1997) at the
University of Washington, derives from partial shielding of the interior
region of the plates from the background zero-point fluctuations of
the vacuum electromagnetic field. As shown by Los Alamos theorists Milonni
et al. (1988), this shielding results in the plates being pushed together
by the unbalanced ZPE radiation pressures. The result is a corollary
conversion of vacuum energy to some other form such as heat. Proof that
such a process violates neither energy nor thermodynamic constraints
can be found in a paper by a colleague and myself (Cole & Puthoff) under
the title "Extracting Energy and Heat from the Vacuum."
Attempts to harness the Casimir and related effects for vacuum energy
conversion are ongoing in our laboratory and elsewhere. The fact that
its potential application to space propulsion has not gone unnoticed
by the Air Force can be seen in its request for proposals for the FY-1986
Defense SBIR Program. Under entry AF86-77, Air Force Rocket Propulsion
Laboratory (AFRPL) Topic: Non-Conventional Propulsion Concepts we
find the statement: "Bold, new non-conventional propulsion concepts
are solicited.... The specific areas in which AFRPL is interested include....
(6) Esoteric energy sources for propulsion including the zero point
quantum dynamic energy of vacuum space."
Several experimental formats for tapping the ZPE for practical use
are under investigation in our laboratory. An early one of interest
is based on the idea of a Casimir pinch effect in non-neutral plasmas,
basically a plasma equivalent of Forward's electromechanical charged-plate
collapse (Puthoff, 1990). The underlying physics is described in a paper
submitted for publication by myself and a colleague (Puthoff & Piestrup,
1997), and it is illustrative that the first of several patents issued
to a consultant to our laboratory, K. R. Shoulders (1991) contains the
descriptive phrase "...energy is provided... and the ultimate source
of this energy appears to be the zero-point radiation of the vacuum
continuum."
Another intriguing possibility is provided by the phenomenon of sonoluminescence,
bubble collapse in an ultrasonically-driven fluid which is accompanied
by intense, sub-nanosecond light radiation. Although the jury is still
out as to the mechanism of light generation, Nobelist Julian Schwinger
(1993) has argued for a Casimir interpretation. Possibly related experimental
evidence for excess heat generation in ultrasonically-driven cavitation
in heavy water is claimed in an EPRI Report (George & Stringham, 1996)
by E-Quest Sciences, although attributed to a nuclear micro-fusion process.
Work is under way in our laboratory to see if this claim can be replicated.
Yet another proposal for ZPE extraction is described in a recent patent
(Mead and Nachamkin, 1996). The approach proposes the use of resonant
dielectric spheres, slightly detuned from each other, to provide a beat-frequency
downshift of the more energetic high-frequency components of the ZPE
to a more easily captured form. We are discussing the possibility of
a collaborative effort between us to determine whether such an approach
is feasible.
Finally, an approach utilizing micro-cavity techniques to perturb the
ground state stability of atomic hydrogen is under consideration in
our lab. It is based on a paper of mine (Puthoff, 1987) in which I put
fo rth the hypothesis that the nonradiative nature of the ground state
is due to a dynamic equilibrium in which radiation emitted due to accelerated
electron ground state motion is compensated by absorption from the ZPE.
If this hypothesis is true, there exists the potential for energy generation
by the application of the techniques of so-called cavity quantum
electrodynamics (QED). In cavity QED, excited atoms are passed through
Casimir-like cavities whose structure suppresses electromagnetic cavity
modes at the transition frequency between the atom's excited and ground
states. The result is that the so-called "spontaneous" emission time
is lengthened considerably (for example, by factors of ten), simply
because spontaneous emission is not so spontaneous after all, but rather
is driven by vacuum fluctuations. Eliminate the modes, and you eliminate
the zero-point fluctuations of the modes, hence suppressing decay of
the excited state. As stated in a review article on cavity QED in Scientific
American (Haroche & Raimond, 1993), "An excited atom that would
ordinarily emit a low-frequency photon cannot do so, because there are
no vacuum fluctuations to stimulate its emission..." In its application
to energy generation, mode suppression would be used to perturb the
hypothesized dynamic ground-state absorption/emission balance to lead
to energy release (patent pending).
An example in which Nature herself may have taken advantage of energetic
vacuum effects is discussed in a model published by ZPE colleagues A.
Rueda of California State University at Long Beach, B. Haisch of Lockheed-Martin,
and D. Cole of IBM (1995). In a paper published in the Astrophysical
Journal, they propose that the vast reaches of outer space constitute
an ideal environment for ZPE acceleration of nuclei and thus provide
a mechanism for "powering up" cosmic rays. Details of the model would
appear to account for other observed phenomena as well, such as the
formation of cosmic voids. This raises the possibility of utilizing
a "sub-cosmic-ray" approach to accelerate protons in a cryogenically-cooled,
collision-free vacuum trap and thus extract energy from the vacuum fluctuations
by this mechanism.
THE VACUUM AS THE SOURCE OF GRAVITY AND INERTIA
What of the fundamental forces of gravity and inertia that we seek
to overcome in space travel? We have phenomenological theories that
describe their effects (Newton's Laws and their relativistic generalizations),
but what of their origins?
The first hint that these phenomena might themselves be traceable to
roots in the underlying fluctuations of the vacuum came in a study published
by the well-known Russian physicist Andrei Sakharov (1968). Searching
to derive Einstein's phenomenological equations for general relativity
from a more fundamental set of assumptions, Sakharov came to the conclusion
that the entire panoply of general relativistic phenomena could be seen
as induced effects brought about by changes in the quantum-fluctuation
energy of the vacuum due to the presence of matter. In this view the
attractive gravitational force is more akin to the induced Casimir force
discussed above, than to the fundamental inverse square law Coulomb
force between charged particles with which it is often compared. Although
speculative when first introduced by Sakharov, this hypothesis has led
to a rich and ongoing literature, including contributions of my own
(Puthoff, 1989, 1993) on quantum-fluctuation-induced gravity, a literature
that continues to yield deep insight into the role played by vacuum
forces.
Given an apparent deep connection between gravity and the zero-point
fluctuations of the vacuum, a similar connection must exist between
these self-same vacuum fluctuations and inertia. This is because it
is an empirical fact that the gravitational and inertial masses have
the same value, even though the underlying phenomena are quite disparate.
Why, for example, should a measure of the resistance of a body to being
accelerated, even if far from any gravitational field, have the same
value that is associated with the gravitational attraction between bodies?
Indeed, if one is determined by vacuum fluctuations, so must the other.
To get to the heart of inertia, consider a specific example in which
you are standing on a train in the station. As the train leaves the
platform with a jolt, you could be thrown to the floor. What is this
force that knocks you down, seemingly coming out of nowhere? This phenomenon,
which we conveniently label inertia and go on about our physics, is
a subtle feature of the universe that has perplexed generations of physicists
from Newton to Einstein. Since in this example the sudden disquieting
imbalance results from acceleration "relative to the fixed stars," in
its most provocative form one could say that it was the "stars" that
delivered the punch. This key feature was emphasized by the Austrian
philosopher of science Ernst Mach, and is now known as Mach's Principle.
Nonetheless, the mechanism by which the stars might do this deed has
eluded convincing explication.
Addressing this issue in a paper entitled "Inertia as a Zero-Point
Field Lorentz Force," my colleagues and I (Haisch, Rueda & Puthoff,
1994) were successful in tracing the problem of inertia and its connection
to Mach's Principle to the ZPE properties of the vacuum. In a sentence,
although a uniformly moving body does not experience a drag force from
the (Lorentz-invariant) vacuum fluctuations, an accelerated body
meets a resistance (force) proportional to the acceleration. By accelerated
we mean, of course, accelerated relative to the fixed stars. It turns
out that an argument can be made that the quantum fluctuations of distant
matter structure the local vacuum-fluctuation frame of reference (Puthoff,
1989, 1991). Thus, in the example of the train the punch was delivered
by the wall of vacuum fluctuations acting as a proxy for the fixed stars
through which one attempted to accelerate.
The implication for space travel is this: Given the evidence generated
in the field of cavity QED (discussed above), there is experimental
evidence that vacuum fluctuations can be altered by technological means.
This leads to the corollary that, in principle, gravitational and inertial
masses can also be altered.
The possibility of altering mass with a view to easing the energy burden
of future spaceships has been seriously considered by the Advanced Concepts
Office of the Propulsion Directorate of the Phillips Laboratory at Edwards
Air Force Base. Gravity researcher Robert Forward accepted an assignment
to review this concept. His deliverable product was to recommend a broad,
multi-pronged effort involving laboratories from around the world to
investigate the inertia model experimentally.
After a one-year investigation Forward (1996) finished his study and
submitted his report to the Air Force, who published it under the title
Mass Modification Experiment Definition Study. The Abstract reads
in part:
"...Many researchers see the vacuum as a central ingredient of 21st-Century
physics. Some even believe the vacuum may be harnessed to provide a
limitless supply of energy. This report summarizes an attempt to find
an experiment that would test the Haisch, Rueda and Puthoff (HRP) conjecture
that the mass and inertia of a body are induced effects brought about
by changes in the quantum-fluctuation energy of the vacuum... It was
possible to find an experiment that might be able to prove or disprove
that the inertial mass of a body can be altered by making changes in
the vacuum surrounding the body."
With regard to action items, Forward in fact recommends a ranked list
of not one but four experiments to be carried out to address
the ZPF-inertia concept and its broad implications. The recommendations
included investigation of the proposed "sub-cosmic-ray energy device"
mentioned earlier, and the investigation of an hypothesized "inertia-wind"
effect proposed by our laboratory and possibly detected in early experimental
work (Forward & Miller, 1967), though the latter possibility is highly
speculative at this point.
ENGINEERING THE VACUUM FOR "WARP DRIVE"
Perhaps one of the most speculative, but nonetheless scientifically-grounded,
proposals of all is the so-called Alcubierre Warp Drive (Alcubierre,
1994). Taking on the challenge of determining whether Warp Drive a
la Star Trek was a scientific possibility, general relativity theorist
Miguel Alcubierre of the University of Wales set himself the task of
determining whether faster-than-light travel was possible within the
constraints of standard theory. Although such clearly could not be the
case in the flat space of special relativity, general relativity permits
consideration of altered spacetime metrics where such a possibility
is not a priori ruled out. Alcubierre's further self-imposed
constraints on an acceptable solution included the requirements that
no net time distortion should occur (breakfast on Earth, lunch on Alpha
Centauri, and home for dinner with your wife and children, not your
great-great-great grandchildren), and that the occupants of the spaceship
were not to be flattened against the bulkhead by unconscionable accelerations.
A solution meeting all of the above requirements was found and published
by Alcubierre in Classical and Quantum Gravity in 1994. The solution
discovered by Alcubierre involved the creation of a local distortion
of spacetime such that spacetime is expanded behind the spaceship, contracted
ahead of it, and yields a hypersurfer-like motion faster than the speed
of light as seen by observers outside the disturbed region. In essence,
on the outgoing leg of its journey the spaceship is pushed away from
Earth and pulled towards its distant destination by the engineered local
expansion of space itself. For follow-up on the broader aspects of "metric
engineering" concepts, one can refer to a paper published by myself
in Physics Essays (Puthoff, 1996). Interestingly enough, the
engineering requirements rely on the generation of macroscopic, negative-energy-density,
Casimir-like states in the quantum vacuum of the type discussed earlier.
Unfortunately, meeting such requirements is beyond technological reach
without some unforeseen breakthrough (Pfenning and Ford, 1997).
Related, of course, is the knowledge that general relativity permits
the possibility of wormholes, topological tunnels which in principle
could connect distant parts of the universe, a cosmic subway so to speak.
Publishing in the American Journal of Physics, theorists Morris
and Thorne (1988) initially outlined in some detail the requirements
for traversible wormholes and have found that, in principle, the possibility
exists provided one has access to Casimir-like, negative-energy-density
quantum vacuum states. This has led to a rich literature, summarized
recently in a book by Matt Visser (1996) of Washington University, St.
Louis. Again, the technological requirements appear out of reach for
the foreseeable future, perhaps awaiting new techniques for cohering
the ZPE vacuum fluctuations in order to meet the energy-density requirements.
CONCLUSIONS
We began this discussion with the question: "Can the vacuum be engineered
for spaceflight applications?" The answer is: "In principle, yes." However,
engineering-wise it is clear that there is a long way to go. Given the
cliché "a journey of 1000 miles begins with the first steps," it is
also clear that we can take those first steps now in the laboratory.
Given that Casimir and related effects indicate the possibility of tapping
the enormous residual energy in the vacuum-fluctuation ZPE, and the
demonstration in cavity QED that portions of the ZPE spectrum can be
manipulated to produce macroscopic technological effects such as the
inhibition of spontaneous emission of excited states in quantum systems,
it would appear that the first steps along this path are visible. This,
combined with newly-emerging concepts of the relationship of gravity,
inertia and warp drive to properties of the vacuum as a manipulable
medium, indicate yet further reaches of possible technological development,
although requiring yet unforeseen breakthroughs with regard to the possibility
of engineering vacuum fluctuations to produce desired results.
Where does this leave us? As we peer into the heavens from the depth
of our gravity well, hoping for some "magic" solution that will launch
our spacefarers first to the planets and then to the stars, we are reminded
of Arthur C. Clarke's phrase that highly-advanced technology is essentially
indistinguishable from magic. Fortunately, such magic appears to be
waiting in the wings of our deepening understanding of the quantum vacuum
in which we live.
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H. E. Puthoff, Ph.D.
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