Ephraim FISCHBACH, et al.
Hypercharge -- Fifth Force
Occasionally, physicists have postulated the existence of a
fifth force in addition to the four known fundamental forces.
The force is generally believed to have roughly the strength of
gravity (i.e. it is much weaker than electromagnetism or the
nuclear forces) and to have a range of anywhere from less than a
millimeter to cosmological scales.
The idea is difficult to test, because gravity is such a weak
force: the gravitational interaction between two objects is only
significant when one is very heavy. Therefore, it takes very
precise equipment to measure gravitational interactions between
objects that are small compared to the Earth. Nonetheless, in
the late 1980s a fifth force, operating on municipal scales
(i.e. with a range of about 100 meters), was reported by
researchers (Fischbach et al.) who were reanalyzing results of
Loránd Eötvös from earlier in the century. The force was
believed to be linked with hypercharge. Over a number of years,
other experiments have failed to duplicate this result, and
physicists now believe that there is no evidence for a fifth
Theory and Experiment
There are at least three kinds of searches that can be
undertaken, which depend on the kind of force being considered,
and its range.
One way is to search for a fifth force with tests of the strong
equivalence principle: this is one of the most powerful tests of
Einstein's theory of gravity, general relativity. Alternative
theories of gravity, such as Brans-Dicke theory, have a fifth
force — possibly with infinite range. This is because
gravitational interactions, in theories other than general
relativity, have degrees of freedom other than the "metric,"
which dictates the curvature of space, and different kinds of
degrees of freedom produce different effects. For example, a
scalar field cannot produce the bending of light rays. The fifth
force would manifest itself in an effect on solar system orbits,
called the Nordtvedt effect. This is tested with Lunar Laser
Ranging Experiment and very long baseline interferometry.
Another kind of fifth force, which arises in Kaluza-Klein
theory, where the universe has extra dimensions, or in
supergravity or string theory is the Yukawa force, which is
transmitted by a light scalar field (i.e. a scalar field with a
long Compton wavelength, which determines the range). This has
prompted a lot of recent interest, as a theory of supersymmetric
large extra dimensions — dimensions with size slightly less than
a millimeter — has prompted an experimental effort to test
gravity on these very small scales. This requires extremely
sensitive experiments which search for a deviation from the
inverse square law of gravity over a range of distances.
Essentially, they are looking for signs that the Yukawa
interaction is kicking in at a certain length.
Australian researchers, attempting to measure the gravitational
constant deep in a mine shaft, found a discrepancy between the
predicted and measured value, with the measured value being two
percent too small. They concluded that the results may be
explained by a repulsive fifth force with a range from a few
centimetres to a kilometre. Similar experiments have been
carried out onboard a submarine (USS Dolphin (AGSS-555)) while
The above experiments search for a fifth force that is, like
gravity, independent of the composition of an object, so all
objects experience the force in proportion to their masses.
Forces that depend on the composition of an object can be very
sensitively tested by torsion balance experiments of a type
invented by Loránd Eötvös. Such forces may depend, for example,
on the ratio of protons to neutrons in an atomic nucleus, or the
relative amount of different kinds of binding energy in a
nucleus (see the semi-empirical mass formula). Searches have
been done from very short ranges, to municipal scales, to the
scale of the Earth, the sun, and dark matter at the center of
A few physicists think that Einstein's theory of gravity will
have to be modified, not at small scales, but at large
distances, or, equivalently, small accelerations. They point out
that dark matter, dark energy and even the Pioneer anomaly are
unexplained by the Standard Model of particle physics and
suggest that some modification of gravity, possibly arising from
Modified Newtonian Dynamics or the holographic principle. This
is fundamentally different from conventional ideas of a fifth
force, as it grows stronger relative to gravity at longer
distances. Most physicists, however, think that dark matter and
dark energy are not ad hoc, but are supported by a large number
of complementary observations and described by a very simple
Ephraim Fischbach, Daniel Sudarsky, Aaron Szafer, Carrick
Talmadge, and S. H. Aronson, "Reanalysis of the Eötvös
experiment", Physical Review Letters 56 3 (1986).
University of Washington Eöt-Wash group, the leading group
searching for a fifth force.
Lunar Laser Ranging 
Satellite Energy Exchange (SEE) , which is set to test for a
fifth force in space, where it is possible to achieve greater
The Tech Online -- Volume 105, Issue 58 (January 22,
Physicists Discover Fifth Force
David P. Hamilton
Physicists at Purdue University believe they have discovered a
fifth elementary force of nature. This postulated force, named
hypercharge, may oppose the force of gravity.
Dr. Ephraim Fischbach and his colleagues have reinterpreted the
results of the experiments of Roland von Eotv"os, a Hungarian
scientist of the early 20th century. Eotvos' work involved a
test of the principle of equivalence, an Einsteinian postulate
stating that gravity affects objects independently of their
composition. Eotv"os found a small but systematic error in his
calculations and declared a null experiment.
The principle of equivalence is one of the fundamental
assumptions of Einstein's General Theory of Relativity. Even the
verification of hypercharge is unlikely to seriously affect the
principle, according to Peter Saulsan, a principle research
scientist for the MIT Department of Physics.
Fischbach declared in the Jan. 6 issue of Physical Review
Letters that Eotvos' error is systematic enough to prove the
existence of an ephemeral force opposed to that of gravity.
Saulson said that Fischbach had found an "astoundingly good"
correlation between the degree of the error and the baryon
number of the tested materials. The baryon number of a material
is equal to the total number of protons and neutrons in its
The extremely localized effect of the hypercharge force would
not significantly damage the theory of relativity, Saulsan said.
The principal differences between hypercharge and gravity
appear to lie in the forces' effective range and strength,
Unlike gravity, whose effects seem to extend to an infinite
distance, hypercharge appears to have a finite range of
approximately 200 meters, he continued.
Two other elementary forces, the strong and weak nuclear
forces, also have finite ranges, although the range of these
forces is more on the order of the diameter of the atomic
nucleus, Saulsan said.
Fischbach also quoted the results of more recent experiments
which seem to support the existence of hypercharge, Saulsan
Experiments conducted as far as one kilometer underground by
Frank D. Stacey of the University of Queensland in Australia
indicate that the force of gravity varies by as much as
seven-tenths of one percent at different depths in the earth.
Other scientists have reported the apparent effects of another
elementary force in experiments conducted at the Fermi National
Accelerator Laboratory in Batavia, Illinois, according to a Jan.
8 article in the New York Times.
The theory of hypercharge could still face some problems,
Saulsan claimed. For instance, Eotvos' "systematic trend" of
error is greater than Stacey's reported gravitometric anomaly by
a factor of more than 20.
Reasonable explanations for this disagreement exist, Saulsan
suggested. He elaborated on the difficulty of Eotvos' original
experiment, which involved the use of a torsion balance which
would respond to gravity while taking the rotation of the earth
Interpreting data from a 60-year-old experiment is also rather
difficult, Saulsan said. In addition, Stacey's work required him
to estimate the density of the rock above him as he conducted
his experiments. These estimates could easily have been in
error, he continued.
Four elementary forces have already been identified. In order
from weakest to strongest, they are: gravity, electromagnetic,
the weak nuclear force, and the strong nuclear force. Scientists
believe that these forces can explain any phenomenon, including
the creation of the universe.
If hypercharge actually does exist, it would be a step away
from physicists' attempts to mathematically unify the elementary
forces of nature, Saulsan said. But widespread acceptance of the
theory would not threaten any physicist's "dearly-cherished
notions," he added.
The theory would still be a "first-rate" discovery if verified,
Tuesday, Jun. 21, 2005
A Fifth Force?
In the famous anecdote, Galileo Galilei clambered to the top of
the Leaning Tower of Pisa, simultaneously dropped cannonballs of
different sizes and found that they all hit the ground at the
same time. He thus convinced the world -- and in the years to
come, Sir Isaac Newton and Albert Einstein as well -- that in a
vacuum all objects, regardless of mass, fall at the same speed.
Galileo's work went unchallenged until last week, when Purdue
University Physics Professor Ephraim Fischbach, three of his
graduate students and S.H. Aronson, a physicist at Brookhaven
National Laboratory in New York, reported discerning a
previously unknown force that causes objects of different masses
to fall at different rates.
If Fischbach is proved right, his hypothetical force, which he
calls hypercharge, would be the fifth known basic force. (Four
forces are known to exist: gravity; electromagnetism; the strong
force, which binds the atomic nucleus; and the weak force, which
is responsible for certain types of radioactivity.) Hypercharge,
Fischbach reports in Physical Review Letters, is an extremely
weak repulsive force that acts between objects no more than
about 600 feet apart and varies in strength from element to
element. It is strongest in iron and weakest in hydrogen. Thus,
the physicists contend, if an iron ball and, say, a feather were
released simultaneously in a vacuum, the iron's repulsive
hypercharge would act more strongly than the feather's to
counteract the earth's gravity--and the feather would hit first.
The team began looking for evidence of hypercharge after
perceiving what Fischbach calls "funny results" in two
contemporary experiments, one involving gravity tests in a deep
mine, the other the behavior of subatomic particles. "We felt
the results could be explained with an additional force," says
Fischbach, "so we went back to the data published by Baron
Roland von Eötvös in Hungary in 1922 to see if we could find
evidence." Eötvös had indirectly measured the speeds at which
objects fall and found small discrepancies, which he attributed
to limitations in his equipment. Re-examining the data, the team
decided that the aberrations were caused by hypercharge. But
other physicists caution that more experiments are necessary
before a firm conclusion can be reached. Says Harvard
University's Sheldon Glashow: "The work suggests an interesting
direction, but by no means should be taken as a real discovery."
Phys. Rev. Lett. 56, 2347 - 2349 (1986)
Hypercharge Fields and Eötvös-Type
Department of Physics, Brookhaven National Laboratory, Upton,
New York 11973
It is shown that Eötvös-type torsion-balance experiments
performed in the vicinity of a large cliff may be used as
sensitive tests for the recently postulated existence of a
medium-range hypercharge force. The residual nonzero effect
found in the original Eötvös results could be mainly due to
terrain irregularities and thus be larger than, but still
correlated to, the effects expected from the Earth's rotation
and the hypercharge hypothesis.
Phys. Rev. Lett. 56, 3 - 6 (1986)
Reanalysis of the Eoumltvös experiment
Institute for Nuclear Theory, Department of Physics,
University of Washington, Seattle, Washington 98195
Daniel Sudarsky, Aaron Szafer, and Carrick Talmadge
Physics Department, Purdue University, West Lafayette, Indiana
S. H. Aronson
Physics Department, Brookhaven National Laboratory, Upton, New
We have carefully reexamined the results of the experiment of
Eötvös, Pekár, and Fekete, which compared the accelerations of
various materials to the Earth. We find that the
Eötvös-Pekár-Fekete data are sensitive to the composition of the
materials used, and that their results support the existence of
an intermediate-range coupling to baryon number or hypercharge.
Antigravity II: A Fifth Force?
John G. Cramer
Sometimes physics moves surprisingly fast, sometimes
dismayingly slowly. In mid-December I wrote my AV column
(Analog, 7/86) on antigravity, a familiar SF concept. That
column was based on a 1957 paper by Bondi on negative mass.
Almost nothing had been published on gravitational repulsion in
the almost 30 years since the appearance of Bondi's paper. The
scientific "field" of antigravity research was essentially
Then, as soon as my column was safely submitted, hot new
results on antigravity appeared. The lead article in the January
6, 1986 issue of Physical Review Letters had the unassuming
title: "A Reanalysis of the Eötvös Experiment" by E. Fischbach,
et al. Two days later the New York Times ran an article with the
headline: "Hints of Fifth Force in Universe Challenge Galileo's
Findings" describing the importance of Fischbach's work.
Peculiar experimental results from terrestrial gravity
measurements and from the behavior of "strange" K-mesons (kaons)
had been explained by a new theory proposing a "hypercharge"
force, a new fifth force of nature which is gravity-like but
which repels rather than attracting nearby masses. This new
antigravity force is the subject of this AV column.
The first thread of this story goes back two centuries to Sir
Isaac Newton. Newton discovered the famous gravitational
"inverse square-law" relation, F12 = Gm1m2/r2, which proved
equally useful in predicting the orbit of the Moon and the force
of gravity at the surface of the Earth. In Newton's equation G
is a fundamental quantity called the universal gravitational
constant. Among the physical constants of nature, G stands out
as being the most uncertain. Fundamental constants (the velocity
of light, the electron charge) are usually known to a few parts
per million, but G, with a value of 6.673 × 10-11 m3/kg-s2, is
known to only about 1 part in 2000.
In a way, it is surprising that G is so poorly known. The
orbits of planets in our solar system depend directly on G and
are both observed and calculated to parts per billion. The
problem is that to obtain G from these data we must have a
completely independent knowledge of the masses involved in the
gravitational attraction. Unfortunately, we have no way,
independent of orbital dynamics, of measuring the masses of the
Earth, Moon, Sun, Jupiter, etc. Therefore, our imprecise
knowledge of G must come from the very weak force of
gravitational attraction observed in the laboratory between two
masses, for example two large lead spheres placed close
But there is another way of measuring G. The oil industry has
developed extremely precise devices for measuring g, the
acceleration due to gravity, both on and beneath the Earth's
surface. The dependence of the acceleration g on depth can be
used to determine the gravity constant G. When the densities of
the rock strata have been well mapped, this determination has an
accuracy comparable to laboratory measurements of G. One would
expect both methods to give the same value of the "constant". It
is a big surprise, therefore, that the geological technique
gives a value of 6.734 × 10-11 m3/kg-s2 (instead of 6.673 ×
10-11). It would appear that this "universal constant" has
significantly different values below the Earth's surface and in
a surface laboratory.
The second thread of the story comes from modern particle
physics. The species of particles called K-mesons or kaons are
unusual among mesons in having a characteristic called
hypercharge, a conserved property of certain particles. The
neutral "matter" kaon is the Ko theoretically a system composed
of a "down" quark and an "anti-strange" quark, has a hypercharge
of +1. Its antimatter twin, the Kő, a strange quark and an
anti-down quark, has a hypercharge of -1. Both Ko's have the
same electrical charge (Q=0), the same spin (s=0), and the same
mass (about half that of a proton). From all external clues
these two theoretical particles are indistinguishable except in
their hypercharge, which is not directly observable.
In this situation where two states of matter cannot be
distinguished externally, quantum mechanics tells us that a very
interesting thing happens. The two indistinguishable states are
"mixed" to make two new states of matter which are
distinguishable. This mixing produces from the combination
(Ko-Kő) the particle KS which decays in about 10-10 seconds (and
so is called K-short). And it produces from the combination (Ko+
Kő) the particle KL which decays 581 times more slowly (and
therefore is called K-long). The KL particle has been found to
be very peculiar in its decay into other particles, showing a
favoritism for one direction of time over another and for matter
over antimatter. These violations of symmetry principles of
nature (time-reversal and charge invariance) are not understood
in any fundamental way.
But more recently another peculiarity of the kaon system has
been discovered which is even more of a puzzle. Detailed studies
of the KL and KS mesons have been made at a number of
accelerator laboratories under a variety of experimental
circumstances. When these experiments are reduced to the few
basic "constants" of the kaon system, for example the KL-KS mass
difference and the KS half-life, these "constants" are found to
depend on the velocity of the kaons with respect to the
laboratory frame of reference. This is not a special relativity
effect; those are already included in the data analysis. In
fact, this velocity dependence cannot be readily accounted for
by any of the four known forces or by any known physical
Prof. Ephriam Fischbach and his colleagues, in the paper
mentioned above, have sought to explain both of these curious
results, the variation of G and the velocity dependence of the
kaon system, with a single theory. They start with the fact that
kaons, neutrons, and protons all have hypercharge. Perhaps, the
paper speculates, there is new and very weak force associated
with hypercharge which is responsible for the anomalies in both
the gravitational and the kaon measurements. Starting from this
point, they calculate the properties which such a "fifth" force
must have to be consistent with these observations. They
conclude that this new force would be very much like gravity,
but with four important differences: (1) it depends on
hypercharge rather than mass; (2) it is a repulsive force, in
that objects with the same hypercharge are repelled from each
other; (3) it has a strength only 0.7% that of gravity; and (4)
it is a "short range" force which cuts off exponentially at
distances on the order of 200 meters.
This last point requires some explanation. Two of the four
known forces of nature, gravity and electromagnetism, are "long
range" forces which fall off as 1/r2 with the distance from a
massive or charged object but otherwise extend to infinity. The
other two known forces, the weak and strong interactions, are
"short range" and cut off to zero at distances on the order of
the size of a nucleus. These differences in range are attributed
to the masses of the "mediating particles" which produce the
forces. Electromagnetism is mediated by the photon and gravity
by the graviton, both particles with zero rest-mass which give
their corresponding forces infinite range. The strong
interaction is mediated by the gluon and the weak interaction by
the Z and W particles, all of which have masses on the order of
that of the proton and give their corresponding forces very
short ranges. According to the "fifth force" hypothesis, the
range of the force which would account for the G measurements
and the kaon anomalies would have to be about 200 meters. This
corresponds to a very light mediating particle (the
"hyper-photon") with a mass about 10-14 that of the electron.
This hypothesis can explain the G difference. Gravitating
objects within a few hundred meters of each other, for example,
the lead spheres in a laboratory measurement of G, feel a 0.7%
repulsion from the hypercharge force which reduces the
attraction slightly and leads to a slightly low measured value
for G. The geological measurements of g, however, record the
gravitational attraction of masses which are typically much more
distant than a few hundred meters and give a value of G
unmodified by hypercharge repulsion.
The hypothesis can also explain the kaon energy dependence. The
Ko and Kő, with opposite hypercharges, are mixed in slightly
different proportions at different velocities because the extra
hypercharge force from the nearby neutrons and protons of nuclei
in the laboratory acts oppositely on them. Thus their invariant
properties become variables. The "true" properties of the kaons,
according to the hypercharge theory, would be obtained if
measurements were made in empty space with no hypercharge field
from nearby matter to modify the Ko+ Kő mixing.
Like any theory, this one need testing. And one "test" has
already been done and seems to agree with the predictions of the
theory. This test was not a new experiment but a re-analysis of
the Eötvös Experiment, the famous experimental comparison of
inertial and gravitational mass performed by a Hungarian count
in the early decades of this century and published only after
his death in 1922. Fischbach and his collaborators realized that
Eötvös should have seen some evidence for the hypercharge force.
The reason is that the hypercharge of a nucleus depends strictly
on the number of neutrons and protons in the nucleus, while the
mass of a nucleus depends also on the binding energy of the
system. Thus an iron nucleus with large binding energy has a
larger hypercharge-to-mass ratio than does a hydrogen nucleus.
To put it another way, a kilogram sphere of water contains fewer
neutrons and protons and has a smaller hypercharge than a
kilogram sphere of iron. Therefore the sphere of water should
fall slightly faster in vacuum than the iron sphere because
there would be a smaller hypercharge force acting on the water
than on the iron. The Eötvös experiment should have shown the
effects of these small modifications of the force of gravity.
And Fischbach's re-examination of the Eötvös data reveals that
indeed the predicted effect does seem to be present in the old
This new theory has had its first experimental confirmation.
Much more work in testing for the hypercharge force needs to be
done, of course, before it can be considered as established.
This is a "hot" topic and many experimental groups, including
one in my own laboratory, are swinging into action to do the
But in the nature of this column, let's assume for the moment
that the hypercharge force is real and consider its science
fiction implications. First, by damn, we have antigravity! But
no dancing in the streets just yet, please! For use in the
"normal" antigravity way in science fiction, the hypercharge
force does have a few problems: (1) it's too weak, and (2) it
only works over a few hundred meters of distance. So we need
some hypercharge "amplifier", some way for getting more
hypercharge without getting more mass. That might be possible if
there were massless particles (maybe hyper-photons or
neutrinos), that had hypercharge without having a proton-size
mass, but none-such are known. Or perhaps there are
"hyper-magnetic" effects when a hypercharged object is moved at
a goodly velocity.
Anyhow, suppose we can overcome this obstacle and produce
vehicles using hyper-repulsion. How might they work? Well, first
of all the range is a problem. At 600 meters above the ground,
the range effect will cut down the hyper-repulsion to only 5% of
what it is at the surface. So the vehicle would be most
effective at distances of 50 meters or less above the surface.
It would resemble the "floaters" and "grav sleds" which are
common SF techno-props, but it would not be directly useful in
space travel or propulsion.
It's worth considering also that in the process of repelling
the ground, the hyper-force on our hypothetical floater would
also tend to repel the passengers. This unpleasant side effect
might be avoided by placing the repulsion sources for minimum
effect on the passengers, perhaps at many points which lie on
the same spherical surface. But passenger-repulsion might also
be turned into an advantage by using it to reduce or nullify the
forces of acceleration. With a suitable hyperfield system
high-performance spacecraft or aircraft might might, by
balancing inertial forces with hyper-repulsion, be able to
accelerate at many g's without squashing pilot and passengers.
Free-fall space habitats might produce simulated gravity with
hyperfield units mounted in the ceilings, with hyper-repulsion
pushing the occupants toward the floor.
Anyhow, stay tuned to this column for further developments on
the hypercharge force. The definitive tests of the theory will
be well in progress by the time you read this column.
G Measurement Anomaly:
S. C. Holding and G. J. Tuck, Nature 307, 714 (1984).
S. H. Aronson, G. J. Bock, H. Y. Cheng, and E. Fischbach,
Physical Review D28, 476 (1983).
Fifth Force Theory:
E. Fischbach, D. Sudarsky, A. Szafer, C. Talmage, and S. H.
Aronson, Physical Review Letters 56, 3 (1986).
R. von Eötvös, D. Pekár, and E. Fekete, Ann. Phys. (Leipzig) 68,
Was a fifth force felt? - Hypercharge or
Baryon Number Theory
Dietrick E. Thomsen
Was a fifth force felt?
Physicists have divided all the motions in the universe into
the domains of four kinds of force: gravity, electromagnetism,
the weak subatomic force and the strong subatomic force or color
force. Each of these has its source in a different property of
material objects --for example, the source of gravity is mass,
while that of electromagnetic forces is electric charge. Now, a
fifth force is suggested.
Such proposals tend to arise from experimental anomalies that
suggest an unknown force may be acting. In the Jan. 6 PHYSICAL
REVIEW LETTERS, Ephraim Fischbach (temporarily at the University
of Washington in Seattle), Daniel Sudarsky, Aaron Szafer and
Carrick Talmadge of Purdue University in West Lafayette, Ind.,
and S. H. Aronson of Brookhaven National Laboratory in Upton,
N.Y., propose that a fifth force was operating in a famous
experiment done in Hungary in 1922 by Roland von Eotvos, D.
Pekar and E. Fekete. The Eotvos experiment, as it is called,
tested the law of gravity by measuring the gravitational
attraction between the earth and various materials, including
metals, woods and even grease or suet. Fischbach and his
co-workers suggest that, unbeknownst to Eotvos and colleagues,
slight differences in the responses of different materials
indicate that in addition to gravity, a small, repulsive force
Fischbach and his co-workers relate this suggested force to a
quality of matter called phpercharge or baryon number. The
baryon number is related to the number of neutrons and protons,
and therefore to the chemical composition of a material--thus
explaining the difference in force for different materials. The
researchers propose a formal similarity between this hypercharge
force and electromagnetism. Just as electromagnetic forces are
carried from object to object by intermediary particles called
photons, so this hypercharge force would be carried by
"hyperphotons.' A number of experiments could test for the
existence of the hypercharge force, including a direct search
for the hyperphotons themselves.
Astrophysics and Space Science, Volume 126,
Number 2 / October, 1986
A Scalar-Tensor Theory and the New
Luis O. Pimentel and Octavio Obregón
[ Department of Physics, Universidad Autónoma
Metropolitana-Iztapalapa, P.O. Box 55-534, CP 09340 Mexico,
D.F., Mexico ]
Abstract --- We present a scalar-tensor theory whose
weak field limit gives exactly the potential proposed by
Fischbach et al. (1986). The three experimental constants G
infin, agr, and lambda are related to three parameters in our
theory. At the level of the theory we have obtained the field
produced by a source. The way this field should couple with a
massive and lsquochargedrsquo particle (baryonic hypercharge) is
a matter beyond the scope of this work.
The Search for Non-Newtonian Gravity
Ephraim Fischbach & Carrick L. Talmadge
Newton's inverse-square law of gravitation has been one of the
cornerstones of physics ever since it was proposed 300 years
ago. One of its most well known features is the prediction that
all objects fall in a gravitational field with the same
acceleration. This observation, in the form of the Equivalence
Principle, is a fundamental assumption of Einstein's General
Relativity Theory. This book traces the history of attempts to
test the predictions of Newtonian Gravity, and describes in
detail recent experimental efforts to verify both the
inverse-square law and the Equivalence Principle. Interest in
these questions have increased in recent years, as it has become
recognized that deviations from Newtonian gravity could be a
signal for a new fundamental force in nature. This is the first
book devoted entirely to this subject, and will be useful to
both graduate students and researchers interested in this field.
This book describes in detail the ideas that underlie searches
for deviations from the predictions of Newtonian gravity,
focusing on macroscopic tests, since the question of
gravitational effects in quantum systems would warrant a
separate work. A historical development is combined with
detailed technical discussions of the theoretical ideas and
experimental results. A comprehensive bibliography with
approximately 450 entries is provided.
Monday, Aug. 15, 1988
Was Sir Isaac All Wet?
By John Langone
As every physics student learns, there are four known forces of
nature: gravity, electromagnetism, a "strong" force that binds
atomic nuclei and a "weak" one that governs certain types of
radioactive decay. Last week researchers at the Los Alamos
National Laboratory announced that they may have found the best
evidence yet for a hypothetical, elusive "fifth force." If
confirmed, their findings could mean that Sir Isaac Newton's
famous inverse- square law of gravity* is in danger of losing
the exalted position it has held for three centuries. "It's like
saying Mom and apple pie's no good anymore," admits the leader
of the gravity project, Geophysicist Mark Ander. "You just don't
do that lightly."
The physicists reached their conclusion as the result of an
experiment conducted in Greenland last summer. They lowered a
supersensitive gravity meter into a mile-deep hole bored in
glacial ice -- chosen because its density is more uniform than
that of rock -- and monitored the gravitational pull as the
meter descended. What occurred was startling: the expected
increase in gravitational force predicted by Newton was there,
but it got stronger faster than expected. Either something was
enhancing the force of gravity or the researchers had come upon
a heretofore unknown, far more complex working of gravity
itself. Or, just possibly, they had made a mistake.
The fifth force, if that is what it is, has been a source of
debate among physicists since its existence was suggested in
1981 by Australian mineshaft experiments. Five years later,
Purdue University Physics Professor Ephraim Fischbach measured a
weak force he called "hypercharge" and theorized that it caused
objects of different composition to fall at different rates.
Since Fischbach's finding, as many as 45 experiments have sprung
up in search of the mystery force, and so far each has served
only to confound rather than clarify the issue.
In some, for example, gravity appears to be enhanced, while in
others it seems to be counteracted. Moreover, findings from a
U.S. Air Force gravity study were even interpreted by some
scientists as evidence of a "sixth force." But if the existence
of an additional force was proved, scientists would have to
readjust their calculations of gravitational force. "It's like
something completely out of left field," notes Los Alamos
Physicist Terry Goldman. "You don't know quite what to do with
Jim Thomas, a physicist at the California Institute of
Technology, praises the technical precision of Ander's
experiment, but cautions that measuring gravity in holes is
inexact at best. He points out, for example, that an aberration
in the earth's crust might have caused the unusual measurements.
"What we're really talking about is the possible modification of
gravity, which is the fourth force," adds Thomas. Even Ander
stresses that rigorous confirmation is needed before he accepts
the results of his Greenland experiment. Says he: "You keep
saying to yourself, 'Gee, I've gotta be wrong -- Newton
certainly can't be wrong.' "
FOOTNOTE: *Newton's law holds that gravitational pull increases
in inverse proportion to the square of the distance between two
Energy Citations Database
( 1986 Mar 31 )
Experimental signals for hyperphotons
Aronson, S.H. ; Cheng, H. ; Fischbach, E. ; Haxton, W.
We discuss experiments for detecting hyperphotons
(..gamma../sub Y/), which are the real quanta of a hypercharge
field whose existence has been suggested by a recent reanalysis
of the Eoetvoes experiment.^It is shown that ..gamma../sub Y/ is
best detected as an unobserved neutral in the decays K/sup +
-/..--> pi../sup + -/..gamma../sub Y/ and K/sub S//sup
0/..--> pi../sup 0/..gamma../sub Y/, and that existing
experimental limits provide nontrivial constraints on the
strength and range of possible hypercharge couplings.
REANALYSIS OF THE EOTVOS EXPERIMENT
By Fischbach, Ephraim Sudarsky,
Daniel Szafer, Aaron
Talmadge, Carrick Aronson, S. H.
LONG RANGE FORCES AND THE EOTVOS EXPERIMENT
By Fischbach, Ephraim Sudarsky,
Daniel Szafer, Aaron
Talmadge, Carrick Aronson, S. H.
ON THE USE OF EOTVOS TYPE EXPERIMENTS TO DETECT MEDIUM RANGE
By Milgrom, Mordehai
EXPERIMENTAL EVIDENCE FOR QUANTUM GRAVITY?
By Goldman, T. Hughes, Richard
J. Nieto, MichaelMartin
A NEW LONG RANGE FORCE?
By Fayet, P.
EFFECTS OF LOCAL MASS ANOMALIES IN EOTVOS LIKE EXPERIMENTS
By Talmadge, Carrick Aronson, S.
H. Fischbach, Ephraim
THE FIFTH FORCE
By Glashow, S. L.
EOTVOS TESTS OF THE NONSYMMETRIC GRAVITATION THEORY AND THE
By Moffat, J. W. Savaria, P.
ABOUT THE EOTVOS EXPERIMENT AND THE HYPERCHARGE THEORY
By Elizalde, E.
REMNANTS OF THE FIFTH FORCE
By De Rujula, A.
A NEW FORCE IN NATURE?
By Fischbach, Ephraim Sudarsky,
Daniel Szafer, Aaron
Talmadge, Carrick Aronson, S. H.
THE FIFTH FORCE
By Fischbach, Ephraim Sudarsky,
Daniel Szafer, Aaron
Talmadge, Carrick Aronson, S. H.
MULTICOMPONENT MODELS OF THE FIFTH FORCE
By Talmadge, Carrick Fischbach,
Ephraim Aronson, S. H.
SEARCHING FOR THE SOURCE OF THE FIFTH FORCE
By Talmadge, Carrick Fischbach, Ephraim
THE FIFTH FORCE: AN INTRODUCTION TO CURRENT RESEARCH
By Fischbach, Ephraim Talmadge, Carrick
PHENOMENOLOGICAL DESCRIPTION OF THE FIFTH FORCE
By Talmadge, Carrick Fischbach, Ephraim
TEN YEARS OF THE FIFTH FORCE
By Fischbach, Ephraim Talmadge, Carrick
Isis, Vol. 86, No. 2 (Jun., 1995), pp. 355-356
Book Review: R. Corby Hovis
The Rise and Fall of the Fifth Force: Discovery,
Pursuit, and Justification in Modern Physics
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