The Allais effect refers to something that is usually deviated from its normal occurrence. It can be seen in the abnormal behavior of the pendulum (a ball like material hanged on a wire to move back and forth) or gravimeters (it measures gravity) which are sometimes said to be observed usually during a solar eclipse. This effect was for the first time reported as unusual slow changes in an astronomical body’s rotational in the plane of oscillation of a Foucault pendulum (a Foucault pendulum is a simple device that is said to be named after a French physicist) during the solar eclipse that took place on June 30, 1954, by Maurice Allais, a French person who won the Nobel Prize in Economics. This effect is named after him.


Allais again reported another such similar observation of the effect during the solar eclipse which took place on October 2 in the year 1959 using the para-conical pendulum which was invented by him. This study made him renowned and hence he won the famous Galabert Prize of the French Astronautical Society in the year 1950’s and this also gave him the honor of the U.S. Gravity Research Foundation for his excellent and a memorable work which he did on gravity. The existence and truth of the Allais effect remain a topic of huge controversy among the scientists of various communities, as this effect when tested has met with inconsistent and irrelevant results for many years and even decades.

Unfortunately, no theory that has come up had ever been able to explain why some solar (and lunar) eclipses show a disturbing behavior and also show different kinds of pendulums and why it only happens sometimes and why the effect is sometimes delayed and failed to explain that why sometimes this happens to before the eclipse this also did not explain why different pendulums are sometimes able to measure the effect and gravimeters. These questions that were once in darkness are now tried to being solved. A decade ago, a few theories and researches suggested various causes to solve the strange Allais effect phenomena.


The very first component of the Allais effect is that during a Solar eclipse the plane of rotation of the pendulum rotates much faster and thus rapidly than as expected naturally during the eclipse. It rotates back and forth more than the normal rotation of the pendulum. The second effect was that during the eclipse, the period of the pendulum decreases; which means the time period of the pendulum decreases. The third effect says that gravity reduces and then increases means it fluctuates more than the normal pendulum does all these behavior were an important clue to the unusual behavior during an eclipse.

Various other experiments as done by other scientists using atomic clocks and gravimeters (used to measure gravity) instead of pendulums also tend to show significant abnormal gravitational effects which as seen can neither be caused by a tidal effect or drift of the gravity measuring devices nor by high-frequency noise which has special patterns. These effects also showed that there was something that causes unusual behavior of different elements during the eclipse.

A famous dutch physicist Chris Duif, who used to survey the field of unusual gravitational behavior in general, concluded that the question remains the same because Allais observations do not completely satisfy all the conventional explanations of these behaviors and that such investigations should still be performed in near future also to see and have a correct explanation of the whole view and its causes.


Findings say that the phenomenon stated above is due to the rotation of the earth, and also according to the traditional physics, the rate of rotation should be the same during an eclipse like any other time when measured. But when Allais did his experiment, he found something different, he found that there was a rate of shift during the eclipse. This was unexpected, and it also gained a lot of criticism because it failed to answer any questions. One of the main arguments that his theory faced was that Allais was not an experimental scientist. Although the experiment that he performed seems simple, if taken into consideration it could be influenced by things such as atmospheric changes of temperature, pressure, and humidity which are normal to occur and can occur during an eclipse.

Eliminating these factors is quite risky, even for an experienced experimentalist because these are natural environmental phenomenon. A second criticism was that there is no clear mechanism for such anomaly that he stated. Even Allais didn’t have a correct explanation for this mechanism beyond some non-traditional effect. Allais again repeated the same effect in 1959, and found to no surprise he found the very same effect with the same observation all over again. In another year again an experiment was performed using a more accurate gravimeter device but it found no such effect, while when a pendulum experiment was held in 1970 some effect was observed still the cause and all other explanations remain unclear for this effect.

However important the Allais effect may be or however controversial this effect maybe it will always remain as an interesting finding and will have various other stories to explain, some explained and some unexplained.

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