Aug 6, 1999: UPDATE - Decrypting
the Eclipse: A
Solar Eclipse, Global Measurements, and a Mystery: On August
11, scientists around the world will attempt to solve a 45 year
mystery: Does a solar eclipse somehow affect the Foucault pendulum?
Read the follow-on story, at
http://science.nasa.gov/newhome/headlines/ast06aug99_1.htm |
"Despite its omnipresence, gravity remains the least
well tested of all the fundamental forces."
Task
Group On Gravity Probe B, National Research Council, Washington,
D.C. 1995
June 17, 1999: On August 11,
1999, millions of people in the Northern Hemisphere will have
one last chance in this millennium to marvel at a total solar
eclipse. The 50 mile wide path of totality will extend from the
western Atlantic ocean, through Europe and Turkey, all the way
across India into the Indian Ocean. At the instant of totality
viewers situated along this narrow path can glimpse some of Nature's
rarest wonders -- "Bailey's Beads," diffraction bands,
and, of course, the Sun's ephemeral corona.
"No matter how many total eclipses you see," says one
veteran eclipse watcher, "every single one is mind-blowing."
Above: The February 16, 1999 annular
solar eclipse as viewed from Western Australia. Based on images
captured by Oliver
Staiger. See also Links
to more eclipse images.
But for at least two NASA researchers, it's not the visual fireworks
that might make August 11 memorable, instead, it's the prospect
of probing a 50 year old mystery. David Noever and Ron Koczor
of the Marshall Space Flight Center have recently been tasked
with checking some hard-to-believe measurements reported 50 years
ago by Nobel laureate Maurice Allais.
In 1959, at the enthusiastic urging of rocket pioneer
Werner von Braun, a peculiar set of physics experiments first
appeared in English as a four-part series in the journal Aero/Space
Engineering. The author, Maurice Allais, was a skilled physicist
with an interest in the behavior of Foucault's
Pendulum. From 1954 to 1960 he made careful observations
of the motion of glass and metallic pendulums with the hope he
would discover some connection between gravity and magnetism.
Despite years of careful work, he never succeeded in finding
a link between those disparate forces, but he did observe something
extraordinary. During the total eclipses of June 30, 1954, and
October 22, 1959, he detected "anomalies in the movement
of the ... pendulum" during the time when the Earth, the
Moon, and the Sun were aligned.
"A remarkable disturbance has been observed at the
time of the total solar eclipse--June 30, 1954. ..[which] cannot
be considered as due to the disturbances of an aleatory order
[chance]. "Neither can it be considered as produced by an
indirect influence of known factors (temperature, pressure, magnetism,
etc.). Finally, it cannot be identified with periodic lunisolar
effects resulting from the actual theory of gravitation."
Maurice
Allais, 1959, from the abstract of his articles in Aero/Space
Engineering
When Allais won the Nobel Prize in 1988 he revisited his experiments
in his acceptance speech and again noted that the phenomena he
observed was "quite inexplicable within the framework of
currently accepted theories" of gravity.
Indeed, Allais
unsettling measurements have received little credence, despite
the fact that he is a Nobel laureate. That may be because his
1988 Nobel prize is in economics, not physics! Nevertheless,
he was well-known to be a skilled physicist. For his careful
experiments in gravitation he won the 1959 Galabert Prize of
the French Astronautical Society and the 1959 annual award from
the United States Gravity Research Foundation.
Left: The August 11, 1999 solar
eclipse will be visible throughout much of Europe, Pakistan,
India, northeast North America and parts of Asia in the Northern
Hemisphere. The path of totality is indicated by the yellow and
blue line. Credit: F.
Espenak, GSFC/ NASA
Allais solar eclipse results are hard to understand, but
he was undoubtedly a meticulous scientist. His experiments were
well-conceived and he repeated his measurements during two solar
eclipses.
"If something strange is happening to Foucault
pendulums during solar eclipses, then it's a real mystery,"
says Noever. "Is it some gravitational effect, a peculiar
manifestation of tides, or something else entirely? The idea
that some unexplained aspect of gravity is at work seems nonsensical
when you consider that it would seem to imply planets spinning
out of their orbits over very long time scales (among other things).
Also, why would the effect show up only during a solar eclipse?
The Sun, the Moon, and the Earth are nearly aligned about once
a month near the time of the new moon. A solar eclipse takes
place when they are precisely aligned. If something is
happening to gravity once a month, wouldn't we have noticed by
now?"
"The bottom line," said Noever, "is this: It's
unlikely, but Allais could have stumbled on to something important.
So, rather than debate a set of 50 year old measurements we're
going to roll up our sleeves and try to detect Allais signal
directly."
The NASA/Marshall
team plans to observe the August 11, 1999, solar eclipse in an
unusual way, with a high precision gravitometer located at the
Marshall Space Flight Center in Huntsville, AL. The gravitometer
is a state-of-the-art gravity sensor tested as part of a Marshall
project entitled "Ultra-high precision gravity measurements".
Noever and Koczor are using this extraordinary device to carry
out sensitive experiments in gravity physics at the Marshall
Space Flight Center. They are also exploring the history of peer-reviewed
gravity research and repeating or recasting experiments that
would benefit from the high precision afforded by the gravitometer.
Allais work falls in this group.
Above: Cutaway view of gravitometer,
with magnetic, thermal and pressure shielding. The instrument
reports very small changes in the gravitational force acting
on a mechanical spring-mass. Gravitational changes are expressed
as the electrical force (measured as voltage) required to maintain
the spring-mass system at a predetermined position (the null
point). The modified LaCoste-Romberg gravitometer (Edcon, Inc.
Denver, CO) measures relative gravity until calibrated against
a reference. The instrument is routinely calibrated along the
10-station Rocky Mountain Calibration range established by NOAA,
Edcon and the Colorado School of Mines. The calibration is validated
by comparing the measure of absolute gravity in Huntsville Alabama
with reference values from the USAF gravity disk.
"If Allais disturbance is real, and if it has something
to do with gravity, then we will be able to measure it to 10
significant digits," says Noever.
Routinely, Noever and Koczor have recorded the gravitational
disturbance of relatively small masses moving in a terrestrial
laboratory--akin to a variation of one part in a billion in the
local gravity field in response to the movements of a nearby
automobile. These sensitivities in mass detection are traditionally
considered appropriate subjects only for studying the kinds of
enormous mass flows found in stars, not the subject for thoughtful
laboratory research. If Allais pendulum experiments prove
correct, then the Marshall experiments may reveal a disturbance
as high as one-thousand on their measurement scale for the instrument--a
relative siren amidst the otherwise quiet background of solar
and lunar influence on Earth.
Above: A typical gravitometer calibration
curve showing the minute variation in relative gravity measured
at two different heights, both separated by less distance than
the average 1 m from floor to table top (or the equivalent altitude
variation in gravity approximately 300 parts per billion in background
gravity per meter of height). Reprinted from Noever, et al. Physica
C, 1997.
"What we will do is what we do most weekdays,"
explains Noever, "that is, we'll measure the gravitational
field in our lab with a precision of about 1 part in 10 billion.
Our eclipse observations will be coordinated with a another research
team in Denver - separated by 1500 miles and 8,000 feet in altitude.
Afterwards we'll compare records and see if we detected anything
unusual."
Noever and his colleagues also
hope to enlist the aid of other scientists around the world with
access to Foucault pendulums, to exactly reproduce Allais
experiments on August 11. There are more than 60 Foucault pendulums
located in museums and entrance halls, and thousands of amateur
versions around the globe. Near the path of totality there are
major Foucault pendulums at the Hall of Justice in Brussels,
St Isaac's Cathedral in Leningrad, the Pantheon in Paris, and
the UN Building in NY. Each one represents an opportunity to
check Allais results.
Above: The pushpin symbols show
some of the major museum and educational locations having large,
publicly viewable Foucault pendulum on display in the United
States.
"The most likely result of our work on August 11 is that
nothing extraordinary will happen," says Noever, "but
you never know. Von Braun himself and certainly Allais would
have smiled to see us revisiting this mystery after 50 years."
As the famous physicist Max Planck once said, "For a theoretician
really worthy of the name, it may be said in passing that nothing
could be more interesting than a fact which runs counter to a
theory .... for him [or her], the real work begins at that point."
Gravitometer research at the Marshall Space
Flight Center is funded by the Marshall Center Director's Discretionary
Fund. |