PHYSICS OF THE ZERO-POINT FIELD - IMPLICATIONS FOR INERTIA, GRAVITATION AND MASS.pdf

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PHYSICS OF THE ZERO-POINT FIELD:
IMPLICATIONS FOR INERTIA, GRAVITATION AND MASS
BERNHARD HAISCH
Lockheed Martin Solar and Astrophysics Laboratory
Dept. 91-30, Bldg. 252, 3251 Hanover St., Palo Alto, CA 94304
email: haisch@sag.space.lockheed.com
ALFONSO RUEDA
Department of Electrical Engineering, California State University
Long Beach, CA 90840
email: arueda@csulb.edu
H. E. PUTHOFF
Institute for Advanced Studies at Austin
4030 Braker Lane, Suite 300, Austin, TX 78759
email: putho®@aol.com
Speculations in Science and Technology , Vol. 20, pp. 99{114, 1997
(preprint version)
Abstract
Previous studies of the physics of a classical electromagnetic zero-point ¯eld (ZPF) have implicated it as a
possible basis for a number of quantum phenomena. Recent work implies that the ZPF may play an even
more signi¯cant role as the source of inertia and gravitation of matter. Furthermore, this close link between
electromagnetism and inertia suggests that it may be fruitful to investigate to what extent the fundamental
physical process of electromagnetic radiation by accelerated charged particles could be interpreted as scattering
of ambient ZPF radiation. This could also bear upon the origin of radiation reaction and on the existence of the
same Planck function underlying both thermal emission and the acceleration-dependent Davies-Unruh e®ect.
If these ¯ndings are substantiated by further investigations, a paradigm shift would be necessitated in physics.
An overview of these concepts is presented thereby outlining a research agenda which could ultimately lead to
revolutionary technologies.
Keywords: zero-point ¯eld; ZPF; stochastic electrodynamics; quantum electrodynamics; quantum vacuum;
inertia; gravitation; dark matter; mass; relativity
Introduction and Overview
In 1901 Planck was successful in deriving a closed mathematical expression that ¯t the then recent measurement
of the spectral distribution of thermal radiation by hypothesizing a quantization of the average energy per mode
of oscillation [1]. This new formulation avoided the so-called ultraviolet catastrophe , the unphysical prediction
of classical theory readily derivable from energy equipartition that the blackbody spectrum should diverge to
in¯nity as º 3 . Planck derived the well-known blackbody function,
½ ( º;T ) =
c 3 µ
dº;
(1)
e hº=kT
¡
1
in which the º 3 catastrophe is overcome by the exponential denominator resulting from his substitution of
discrete for continuous energy intervals. The expression is factored here to show the two components of density
of modes (i.e. number of degrees of freedom per unit volume) times the thermal energy per mode in the frequency
interval . As discussed in detail in Kuhn's monograph Black Body Theory and the Quantum Discontinuity:
1894{1912 [2], Planck himself remained skeptical of the physical signi¯cance of his mathematical assumption
and of his apparently new constant, h , for over a decade. In 1913 Bohr [3] made quantization of atomic energy
levels a postulate, thereby laying a foundation for quantum physics based upon Planck's unit of quantization.
That same year Einstein and Stern published a paper [4] studying the interaction of matter with radiation
using classical physics and a model of simple dipole oscillators to represent charged particles. They remarked
1
8 ¼º 2
that if, for some reason, such a dipole oscillator had a zero-point energy, i.e. an irreducible energy even at T =0,
of , the Planck formula for the radiation spectrum would result without the need to invoke quantization. a In
1916 Nernst published an article [6] in which he proposed that the Universe might actually contain enormous
amounts of such zero-point radiation. In fact, the existence of such a zero-point ¯eld (ZPF) had been ¯rst
envisaged by Planck around 1910 when he formulated his so-called second theory: namely an attempt to
derive the blackbody spectral formula with a weaker quantization assumption. It was Nernst who captured the
paramount thermodynamic implications and relevance of such a sea of background radiation and became the
main proponent of this concept. Both Planck and Nernst used the correct (1 = 2) form for the average energy
of the zero-point electromagnetic °uctuations instead of the value assumed later by Einstein and Stern; the
assumption is correct for the sum of interacting harmonic oscillators plus the energy of the electromagnetic
¯elds. The electromagnetic blackbody spectrum including ZPF would then be:
½ ( º;T ) =
c 3 µ
+
2
dº:
(2)
e hº=kT
¡
1
While this once again appears to result in a º 3 ultraviolet catastrophe, that is not the case because this
component now refers not to measurable excess radiation from a heated object, rather to a uniform, isotropic
background radiation ¯eld that cannot be directly measured because of its homogeneity. This approach to
understanding the blackbody spectrum was not developed further thereafter, and was in fact essentially forgotten
for the next ¯fty years. What happened instead was that with the success of quantum mechanics, and then
quantum electrodynamics, the generalization and existence of an equivalent to the ZPF, the quantum vacuum,
was taken to be a consequence of quantum laws. In other words, a quantum version of the ZPF became an
accepted part of physics whose existence was interpreted as being due to quantum laws.
In recent years there has been a growing interest in reviving the original semi-classical approach and
exploring its rami¯cations. The motive until recently, besides gaining intuitive insights and calculational ease,
has been to see to what extent various quantum phenomena could be explained solely on the basis of classical
physics with a random perturbing radiation ¯eld | the ZPF | providing quantum-like °uctuations. This
would (again) reverse the cause and e®ect of ZPF vis-a-vis quantum physics. This area of physics is known
as Stochastic Electrodynamics , SED. For a recent short but still comprehensive review see [7] which also gives
valuable references to other older but thorough reviews. SED is also discussed in the monograph by Milonni
[8]. The general idea that the origin of quantization was to be found in some classical stochastic subquantum
background was very much in the air among the founders of modern physics [9]. In 1966, Nelson published a
seminal paper [10] stating:
We shall attempt to show in this paper that the radical departure from classical physics produced by
the introduction of quantum mechanics forty years ago was unnecessary. An entirely classical derivation
and interpretation of the Schrodinger equation will be given, following a line of thought which is a
natural development of reasoning used in statistical mechanics and in the theory of Brownian motion.
Examining the Heisenberg uncertainly principle Boyer [11] showed that for the harmonic oscillator the
°uctuations caused by the ZPF on the positions of particles are exactly in agreement with quantum theory.
Recently Rueda [12] has arrived at the Schrodinger equation, albeit in a restrictive context that invokes a
ZPF-induced Brownian-motion model.
The most optimistic outcome of the SED approach would be to demonstrate that classical physics plus
a classical electromagnetic ZPF could successfully replicate all quantum phenomena, a situation which would
undermine some of the present ontological basis of quantum physics. While successful up to a point, SED has
not yet achieved this.
As dramatic as a substitution for quantum physics would be on the part of SED, recent studies have
identi¯ed even more profound roles that the ZPF may play in the foundation of physical laws, the constitution
of matter, and the structure of the Universe.
(1) The inertia of matter may be due to a Lorentz force-like electromagnetic interaction between charge at the
quark or fundamental lepton level and the ZPF [13, HRP].
(2) There appears to be an analogous electromagnetic vacuum origin for gravitation | as there would neces-
sarily be from the principle of equivalence | an idea originally proposed by Sakharov [14] [15]. It needs
a Several such derivations of the blackbody function using classical physics with a real zero-point ¯eld but
without quantization have been published by Boyer; cf. [5] and references therein.
2
8 ¼º 2
 
to be shown that this can be made mathematically equivalent to curved space-time. The approach that
Einstein took in 1911 [16] (with later corrections [17]) involving a speed of light which is dependent on
gravitational potential, c (©), suggests a promising avenue.
(3) Matter and the concept of mass would appear to be secondary phenomena arising out of charge-ZPF
interactions: energy, charge and electromagnetic ¯elds being primary.
(4) The creation of electromagnetic radiation by accelerated charge may possibly be interpretable as scattering
of ambient ZPF radiation. In stationary frames the scattering of ZPF radiation by a dipole is an equilibrium
process [18]; the asymmetry in the scattering process when an accelerated dipole is viewed from a stationary
laboratory frame would appear to be the source of what is customarily interpreted as radiation emitted by
accelerated charge (see pp. 114{120 of [19]).
(5) In the ideal case of the Bohr atom, the stability of the ground state of the hydrogen atom can be attributed
to energy absorption from the ZPF rather than Bohr's postulated quantum prohibition [11] [20].
(6) Spontaneous emission can be interpreted at least in part (one half of it to be precise) as emission stimulated
by the background ZPF. As McCrea has argued [21], this places the ZPF in the role of a kind of universal
clock governing seemingly spontaneous phenomena.
(7) Even within general relativity, non-gravitational accelerations require a frame of rest that is absolute in
either the Newtonian or the Machian sense [22][23][24]. However owing to special relativity, such a frame
cannot be absolute with respect to uniform rectilinear motions. This seemingly impossible requirement is
actually met by the ZPF. Owing to its º 3 spectrum it has a Lorentz invariant energy density spectrum, yet
acquires certain asymmetries as viewed from an accelerating frame ::: which leads, among other things,we
think, to inertia, thus providing a quantitative, modern version of Mach's principle [HRP].
(8) The structure of the Universe on the largest scale | voids and sheets | can be attributed to the ZPF via
an Einstein-Hopf type acceleration process [25][26][27]. The same acceleration process may also underlie
cosmic rays [5][28].
The objective of this paper is not to establish the veracity of these paradigm-shifting possibilities; some
are clearly speculative at this time, e.g. in the case of (8), caveats exist concerning the Einstein-Hopf process.
A recent evaluation of this appears in a review published by de la Pena and Cetto after acceptance of this
paper [29]. Our goal is to present an overview of reasonably justi¯ed conclusions concerning the ZPF based
upon published work and to extrapolate to new research programs that may come about, clearly identifying
speculations as such. The intellectual and perhaps even technological rewards that would be forthcoming should
such a research agenda succeed may attract innovative scientists to examine these possibilities in su±cient detail
so that in a few years we may know whether this approach has been an intoxicating but illusory deadend or the
path to a new paradigm for the next millenium.
If the ZPF is real, why is it not detectable?
The most universal real radiation ¯eld we are familiar with today is the cosmic microwave background
(CMB). While the NASA COBE measurements, published in 1992, ¯nally found minute inhomogeneities, to
high precision the CMB can be considered as quite uniform and isotropic, yet readily detectable. That being
the case, why is the ZPF not equally evident? The ratio of the two is simply the ratio of the two terms in eqn.
(2) taking T =2 : 73 K. At the 53 GHz-frequency middle band of the COBE Di®erential Microwave Radiometer
this ratio would be ½ ZPF CMB =0 : 77. Even more dramatically, in the optical spectrum, eqn. (2) predicts
that the ZPF should be about two orders of magnitude brighter than the Sun. Why are we not blinded by the
ZPF?
To ¯rst order, in the absence of special conditions (discussed below), the ZPF is isotropic and homogeneous
in its spatial distribution. This must be the case even inside matter due to the characteristics of the ZPF
that dipole transitions absorb and re-emit this isotropic, º 3 radiation without change in spatial or spectral
distribution [11][18]. Therefore matter that might ordinarily be considered opaque to radiation of a given
frequency e®ectively passes on the ZPF radiation without attenuation, i.e. the radiation may be absorbed and
re-emitted many times, but the net e®ect is nil. In such fashion the ZPF resists direct observation. Only
deviations \above" the ZPF are measurable.
To second order, however, the presence of the ZPF can be registered indirectly, not on the basis of absorption
and reemission, but rather by correlation or interference e®ects. In the case of closely-spaced atoms or molecules,
3
for example, the absorption and reemission of the ZPF radiation results in the generation of secondary short-
range ¯elds (even at temperatures of absolute zero) that, because of their correlating e®ects, result in short-range
attractive forces: the so-called van der Waals forces. Similarly, in a macroscopic version of the same phenomenon,
a unique attractive quantum force (the Casimir force) between dielectric or conducting plates can be shown to
exist on the basis that absorption and reemission of the ZPF radiation by the plates results in interference and
cancellation of certain electromagnetic modes between the plates. The result is an imbalance in the associated
ZPF radiation pressures interior and exterior to the plates, hence a net force of attraction between the plates;
a close parallel can be drawn between this phenomenon and the familiar concept of radiation pressure [30a].
Again, the ZPF background is inferred from its consequences rather than from direct observation. Indeed, at
a deeper level, the various phenomena listed above in (1) through (8) can all be taken as con¯rmation and
perhaps even as indirect \observations of the ZPF" in the sense that their elucidation is most parsimonious in
terms of the ZPF interpretation.
Inertia and Mach's Principle
= ma
? Newton's equation of motion is a good starting point for discussion. Consider a slight variation of it. Some
of the largest scale motions in the Universe involve extremely small accelerations: The v 2 =r acceleration of the
Sun around the Milky Way galaxy amounts to a
10 kpc).
This is typical of rotational accelerations in outer galactic regions. Accelerations of galaxies within clusters are
on a similar scale. Such small accelerations would be extremely di±cult to create and measure in a laboratory,
and to that extent, the F = ma relation is terra incognita in this regime. Without implying any judgement
as to the validity of the proposal, we note that an alternate explanation to the existence of dark matter as a
cause of non-Keplerian galactic rotation curves, etc., involves hypothesizing a non-linear F = ma relationship
for accelerations in this regime [30b]. The point is not to promote this particular hypothesis, merely to point
to a conceivable application for a more complex view of inertia. b
»
2
£
10 ¡ 8
cm s ¡ 2
(taking v
»
250 km/s and r
»
A discussion of Mach's principle could ¯ll volumes [31]; it was an important consideration for Einstein
in his development of general relativity (GR) [17] [32], and while he initially thought that GR incorporated
Mach's principle, a GR-solution for a universe devoid of matter was discovered by Einstein himself [33], and a
solution for a rotating universe by Godel, both demonstrating that Mach's principle was not compatible with
GR. Mach argued that all motions must be relative. That being the case, whether one chooses for purposes
of analysis a rotating earth or a stationary earth and a counter-rotating universe should not matter. But
what would be the origin of centrifugal force in the latter view, deforming the shape of the earth to make it
equivalent to the rotating-earth perspective. Mach proposed that the solution lies in the circumstance that the
local property of inertia of any material object is caused by the surrounding matter. In this way a rotating
universe could conceivably induce an equivalent of centrifugal force in a stationary earth. This view would also
be consistent with the idea that it should not make sense to allow a measurable perception of rotation (again
from centrifugal or Coriolis forces) if an object were rotating in an empty universe, i.e. rotating with respect to
what? In Mach's view such rotation would be an absurdity, and without the presence of other matter available
to create inertia the conundrum is avoided. The only long-range force available being gravitation, a Machian
inertia must somehow be related to gravity. A preliminary Newtonian model of this was proposed by Sciama
[33] in which gravitation arises via the usual scalar potential, © =
¡ R V ( ½=r ) dV , while inertia arises via the
next higher extension, a vector potential, A =
=c ) v ( t ). It can readily be shown that in this view matter
on a cosmological distance scale would predominate in the origin of (local) inertia. No entirely satisfactory
formulation of Mach's principle has been developed [34]. Moreover, asymmetries such as those measured by the
NASA Cosmic Background Explorer, the mass-asymmetry due to our location in the Milky Way, etc., do not
give rise to a measurable asymmetry in inertia, i.e. mass is not a vector quantity. Remarkable upper limits can
be placed on this thanks to the Hughes-Drever experiments: ¢ m=m
¡
·
10 ¡ 20
[35] whereas Sciama's approach
[33] would predict ¢ m=m
»
10 ¡ 7
due to the Milky Way.
The concept developed by us [HRP] is di®erent. Inertia does result from something external: not other
matter but the ZPF, with the e®ect, at the ¯rst level of the analysis at least, being entirely local. In HRP we
b Should the ZPF inertia theory result in a prediction of a non-linear inertia in the regime hypothesized by
Milgrom, this would of course be a plus for the theory resolving a major astrophysical puzzle | the nature of
dark matter | in a quite unexpected way.
4
That matter should have the property of inertia is so fundamental to our conception of physical reality
that it is di±cult to imagine how matter could not have such an innate property. How could one have a stable,
solid (including liquid and gas in this context) reality without inertia? Put another way, how could F
analyzed the forces on a Planck oscillator when subject to acceleration using the methods of SED. Analytically,
we set a point-charge (termed a parton: this could represent a quark or an electron for example) into harmonic
motion driven by the random °uctuations of the ZPF. These °uctuations are perfectly symmetrical in stationary
or uniform-motion frames. It was discovered by Davies [36] and by Unruh [37] that acceleration-dependent terms
arise in the spectral energy density of the ZPF (cf. equation 3 of HRP). One of these is a pseudo-Planckian
component of the ZPF involving an acceleration-temperature (cf. equation 2 of HRP), a very small term under
ordinary accelerations. The other term is an acceleration-squared modi¯cation of the spectral energy density.
In HRP we investigate this term. Following the technique of Einstein and Hopf and the identical con¯guration
used by Boyer [38] to derive the Davies-Unruh e®ect in the context of SED, we investigated the heretofore
unexplored v
£
a . The Lorentz force
resists acceleration in a linear way. We interpret the inertial resistance to acceleration of matter to be this
electromagnetic Lorentz force; inertia would thus be electromagnetic in origin . This is, in e®ect, a derivation
of F = ma from the electrodynamics of ZPF-charged particle interactions. The inertial mass, m i , is then a
function of electrodynamic parameters,
£
B ZP >
m i =
¡ h! c
2 ¼c 2
(3)
200 di®erence between an electron and a muon in spite of
their identical charge. For a composite particle such as a proton (made of uud quarks) or neutron (made of udd
quarks) the inertia-producing interactions would take place with the individual quarks; at very high frequencies
quarks would oscillate essentially independently given the nature of the strong interaction, so-called asymptotic
freedom (\At close range, jostling around inside a proton, quarks barely notice one another's presence and act
like independent particles." [39]); di®erences in the sign of the charge would only change the phase of the
oscillations giving rise to the Lorentz force, not the direction, thus making the e®ect on the individual quarks
in a nucleon additive.
»
The HRP analysis has been criticized for using an Abraham-Lorentz-Dirac (ALD) equation of motion as a
basis, the argument being that we are \using Newton's law to derive Newton's law." This is not the case since
the ALD equation is phenomenologically invoked as an SED resource solely to bring about oscillations in a plane
with the Lorentz force arising independently out of the magnetic component of the ZPF in a perpendicularly-
accelerating direction. Other justi¯ed criticisms involve the use of an ideal parton to represent charged matter
and general mathematical complexity.
All of these problems will be addressed and hopefully swept aside by a new approach in which one considers
solely the time evolution of the momentum-°ux derived from the Poynting vector of the ZPF in a uniformly
accelerating coordinate system [40][41]. This new analysis does not concern itself with particle-ZPF interactions
other than to assume that ZPF radiation can be scattered by charged matter. Using entirely straightfor-
ward Lorentz transformations of the electromagnetic ¯eld one can derive the analogous result to HRP: viz, an
acceleration-dependent resistance originating in such scattering of radiation. Moreover this analysis has the
merit of not only being analytically simpler than HRP, but also of being relativistic, i.e. one can derive the
relativistic form of Newton's law in this fashion:
F
= d
P
=d¿ , the well-known four-vector form applicable to
particles accelerated to high speeds.
Gravitation
All experiments and observations to date are consistent with predictions of general relativity. The math-
ematical treatment of gravitation as a space-time curvature works well. However if it could be shown that a
di®erent theoretical basis can be made analytically equivalent to space-time curvature, with its prediction of
gravitational lensing, black holes, etc. this would reopen the possibility that gravitation is a force. Einstein
himself \did not think that electromagnetism and gravity should remain separate, and spend the later years of
his life searching for a theory of `electro-gravity' to complete the work begun by Maxwell" [39]. The following
5
B ZP force that the driven-oscillator would experience in an accelerating frame. The v are
the oscillatory motions in a plane due to the electric driving forces, E ZP , of the ZPF. The oscillator is then
forced to undergo a uniform acceleration, a , in a direction perpendicular to the plane of oscillation ; the resulting
Lorentz force after proper stochastic averaging turns out to be such that <v
/
where ¡ is a damping constant for the oscillations and ! c relates to a characteristic frequency of particle-ZPF
interactions. In HRP, ! c was taken to be either a ZPF cuto® frequency (the Planck frequency) or a re°ection
of the minimum parton size (the Planck length) which would translate into the same cuto® frequency. We
speculate that in more re¯ned future versions of the theory this simple ! c cut-o® parameter will actually be
replaced by a resonance frequency, ! 0 , and that di®erences in resonance are factors determining di®erences in
masses of fundamental particles, i.e. the factor of
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