Peering through a Hole in the Sky
NASA/Marshall scientists will probe an unlikely 50-year
old mystery during the August 11, 1999 total solar eclipse
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
"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
"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.
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"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.
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.
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"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."
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
"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."
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.
The Millennium's Last Solar Eclipse -- from Sky &Telescope
Fred Espenak's Solar Eclipse Home Page -- at the NASA/Goddard Space Flight Center
Autobiography of Maurice Allais -- Copyright ©1999 The Nobel Foundation
The Foucault Pendulum -- a excellent tutorial discussion by by Professor B. Nickel, Physics Department, University of Guelph. This web site also reviews some peculiarities in pendulum motion detected by experiments at the University of Guelph.
M. Allais, Aero/Space Engineering, Sept. 1959, p. 46-52; Aero/Space Engineering, Oct. 1959, p. 51-55; Aero/Space Engineering, Nov. 1959, p. 55; C.R.A.S. (Fr.), 247,1958, p. 1428; ibid, p. 2284; C.R.A.S. (Fr.), 248,1959, p. 764; ibid, p. 359
A partial list of gravity anomaly news and research
Three Spacecraft Reveal Unexplained Motions -- from Newswise
Unexplained sunward deceleration -- Dr. John Anderson, a planetary scientist at NASA's Jet Propulsion Laboratory John D. Anderson, Philip A. Laing, Eunice L. Lau, Anthony S. Liu, Michael Martin Nieto, Slava G. Turyshev, Phys.Rev.Lett. 81 (1998) 2858-2861, reported acceleration residuals ~8(+3)x10-8 cm/s2 directed towards the Sun, or approximately 0.1 nano-g (where g=980 cm/s2 ).
Big Bang Acceleration -- Observations of supernova explosions halfway back to the Big Bang give plausible evidence that the expansion of the universe has been accelerating since that epoch, approximately 8 billion years ago and suggest that energy associated with the vacuum itself may be responsible for the acceleration. R.P. Kirshner, Harvard-Smithsonian Center for Astrophysics, Proc. Natl. Acad. Sci. 96, 4224-4227 (1999).
The Foucault Pendulum
Since its accidental discovery prior to the 1851 Worlds Fair, the Foucault pendulum has become recognized as the first wholly non-astronomical demonstration of the Earths rotation. In brief, when a mass on a wire is set in motion over the course of hours, its azimuthal direction will rotate with the Earths axial spin. An especially clear demonstration would arrange a rim of sand or pegs along the periphery of the pendulums maximum swing--a sort of sand fortress surrounded by a moat of semi-permanent wooden soldiers. As the day progresses, each soldier gets knocked down in the path of one circular turn of the pendulum. Either at the North or South pole particularly, each mark on the full circumference would have been visited exactly once per day--a phenomenon called the Foucault effect. Amazingly, from a closed room with no outside view of any time passage, it is possible to observe the Earths rotation using this classical demonstration of the pendulums inertial interplay with the Earths rotation and gravity. Relative to the stars, the floor under the pendulum turns.
The link, above, will transport you to an excellent web site maintained by the Physics Department at the University of Guelph. It includes a historical and tutorial discussion of Foucault's pendulum and a review of some anomalies in pendulum motion measured at the University of Guelph.
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NASA Official: Ron Koczor