23 lines
5.3 KiB
Markdown
23 lines
5.3 KiB
Markdown
---
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title: "Allais effect"
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chunk: 1/2
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source: "https://en.wikipedia.org/wiki/Allais_effect"
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category: "reference"
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tags: "science, encyclopedia"
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date_saved: "2026-05-05T09:14:05.167652+00:00"
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instance: "kb-cron"
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---
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The Allais effect is the alleged anomalous behavior of pendulums or gravimeters which is sometimes purportedly observed during a solar eclipse. The effect was first reported as an anomalous precession of the plane of oscillation of a Foucault pendulum during the solar eclipse of June 30, 1954 by Maurice Allais, a French polymath who later won the Nobel Prize in Economics. Allais reported another observation of the effect during the solar eclipse of October 2, 1959 using the paraconical pendulum he invented. This study earned him the 1959 Galabert Prize of the French Astronautical Society and made him a laureate of the U.S. Gravity Research Foundation for his 1959 memoir on gravity. The veracity of the Allais effect remains controversial among the scientific community, as its testing has frequently met with inconsistent or ambiguous results over more than five decades of observation.
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== Experimental observations ==
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Maurice Allais emphasized the "dynamic character" of the effects he observed:
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The observed effects are only seen when the pendulum is moving. They are not connected with the intensity of weight (gravimetry), but with the variation of weight (or of inertia) in the space swept by the pendulum. Actually, while the movement of the plane of oscillation of the pendulum is inexplicable by the theory of gravitation, the deviations from the vertical are explained perfectly by that theory. The deviations from the vertical […] correspond to a static phenomenon, while my experiments correspond to a dynamic phenomenon.
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Besides Allais's own experiments, related research about a possible effect of the Moon's shielding, absorption or bending of the Sun's gravitational field during a solar eclipse have been conducted by scientists around the world. Some observations have yielded positive results, seemingly confirming that minute but detectable variations in the expected behavior of devices dependent on gravity do indeed occur within the umbra of an eclipse, but others have failed to detect any noticeable effect.
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=== Anomalous results ===
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Romanian physicist Gheorghe Jeverdan et al. observed the Allais effect and the so-called Jeverdan-Rusu-Antonescu effect or Jeverdan effect (i.e. the change in the oscillation period of a pendulum during an eclipse) while monitoring a Foucault pendulum during the solar eclipse of February 15, 1961. The authors made two hypotheses regarding their observation: during an eclipse, the Moon exerts a screening effect on the gravitational attraction of the Sun so that the attraction of the Earth is indirectly increased, a phenomenon that could also be studied with tides. If the hypothesis of the screening effect is wrong, another explanation could be that the variation of the Earth's gravity might be considered as a result of the diffraction of gravitational waves. Erwin Saxl and Mildred Allen similarly reported strong anomalous changes in the period of a torsion pendulum during the solar eclipse of March 7, 1970 and concluded that "gravitational theory needs to be modified".
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Dr. Leonid Savrov of the Sternberg Astronomical Institute built a dedicated paraconical pendulum to test the Allais effect during the solar eclipse of July 11, 1991 in Mexico and the eclipse of November 3, 1994 in Brazil. While he could not observe Allais's claim that there is a diurnal periodicity in the motion of a paraconical pendulum, he did, however, write: "The most interesting result of the Mexico and Brazil experiments is the increase of rotational velocity of the pendulum oscillation plane in the direction of the Foucault effect during the eclipse. It seems that we have some kind of special effect."
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Various other experiments using atomic clocks and gravimeters instead of pendulums also recorded significant anomalous gravitational effects which can neither be caused by a tidal effect or drift of the gravimeters, nor by high-frequency noise which has special patterns. These experiments were set up by different teams during solar eclipses in China in 1992, India in 1995, and China in 1997.
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Results reporting the observation of the Allais and Jeverdan-Rusu-Antonescu effects during the annular solar eclipse of September 22, 2006 were presented the following year by a Romanian team, with a quantization of the behavior of the paraconical pendulum. During the solar eclipse of August 1, 2008, a Ukrainian team and two Romanian teams worked together hundreds of kilometers apart with different apparatuses: five independent miniature torsion balances for the Ukrainian team, two independent short ball-borne pendulums for a Romanian team and a long Foucault pendulum for the third team. All three teams detected unexplained and mutually correlated disturbances. The same teams repeated a dual experiment during the annular solar eclipse of January 26, 2009, this time outside of the umbra, with the same significant correlation between the behavior of light torsion balances and a Foucault pendulum. They also registered similar anomalies using a Foucault pendulum and a very light torsion balance, both located underground in a disused salt mine with minimal interference, during the partial solar eclipse of June 1, 2011. |