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October 6, 1991
GRAV5.ASC
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This file shared with KeelyNet courtesy of Tom Albion.
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Weighty Matters
Could Newton's 300-year-old law of gravity
finally be succumbing to age?
Several recent findings seem to deviate from the theory, and now the
most meticulous test yet--a measurement of the gravitational field
in a mile-deep borehole in the Greenland ice sheet--has turned up
further evidence of a discrepancy.
The implications could be profound. Such small adjustments to
gravity are in fact predicted by all the most promising attempts to
forge a unified theory of the fundamental forces--the ultimate goal
of physics.
These new effects, which some people call a fifth force and even a
sixth force, are expected to compare to gravity in strength, but
they act over perhaps a few hundred or thousands of meters, whereas
gravity has an infinite range.
One possibile consequence of such new effects is that within the
range of the new forces, Newton's inverse-square law (the strength
of gravity falls as the square of the distance between two masses)
may not be true.
Another is that unlike standard gravity, which acts only on mass,
the new effects may depend on some aspect of an object's
composition, such as the total number of baryons (protons and
neutrons).
Nearly a dozen experiments have sought--inconclusively--to detect
one of the effects (see "Force of a Different Color" in "Science and
the Citizen," December, 1987). The Greenland project is the latest
in a series of attempts to detect a violation of the inverse-square
law by measuring local gravitational fields and comparing them to
calculations based on the density of the surrounding terrain.
An earlier experiment done inside an Australian mine found a
repulsive effect of roughly 1 percent of the strength of ordinary
gravity, acting over a range of a few hundred meters.
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A second experiment, carried out on a 600-meter television tower in
North Carolina, found an attractive effect of about 2 percent of the
strength of gravity acting over a distance of 300 meters.
The calculations worked out even better WHEN BOTH AND ATTRACTIVE AND
A REPULSIVE EFFECT WERE PRESUMNED.
Skeptics argue that these apparent effects could result from
anomalies in local mass density, such as a hidden lode of metal ore.
The Greenland group, led by Mark E. Ander of the Los Alamos National
Laboratory and Mark A. Zumberge of the University of California at
San Diego, therefore chose a highly homogeneous site: a borehole
surrounded by a two-kilometer-thick expanse of ice.
The team took elaborate precautions: the bedrock was mapped by
42,000 high-frequency radar scans, and careful surveys determined
the height of the ice surface to within a centimeter.
A gravimeter took more than 100 readings at half a dozen locations,
at depths of between 200 and 1,600 meters.
The researchers assumed the density of the bedrock might range
between 2.7 and three grams per cubic centimeter; densities outside
this range are geologically improbable. Finally, different members
analyzed the data at least three times.
Their preliminary conclusion:
there appears to be a single, attractive effect whose
strength is between 1.7 and 3.9 percent that of gravity.
It is thought to act over a distance of somewhere between 10
meters and slightly more than one kilometer.
The new findings agree with the results from North Carolina but seem
to contradict those from Australia. It may be possible to reconcile
all three results by including both an attractive and a repulsive
effect, but then the theoretical model "gets rather contrived,"
according to Ander's colleague Richard Hughes.
To help determine whether these effects are real or are instead
caused by hidden anomalies in the environment, the group is already
planning future experiments in the Pacific Ocean and in Antarctica,
where the ice is twice as thick as the ice in Greenland.
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See CENTER1 and the GRAV & GRAVITY series on KeelyNet
for other gravity anomalies.
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as this paper covers, please upload to KeelyNet or send to the
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Thank you for your consideration, interest and support.
Jerry W. Decker.........Ron Barker...........Chuck Henderson
Vangard Sciences/KeelyNet
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