The history of viewing gravity-related phenomena when solar eclipses occur is lengthy, and the narratives surrounding an eclipse’s “totality” are even more substantial.
The moon moving between the earth and the sun represents the occurrence of a solar eclipse, with the moon covering the sun either fully or partially. This happens only during a new moon when the sun and the moon’s orbits are linked. In 2026, it is estimated that five eclipses will occur, but only two of those eclipses will be true total eclipses. Total eclipses are rare in that their totality exists only through the progression of a thin course along the earth’s surface delineated by the moon’s umbra.
The Sun’s Effect
How do we observe a solar eclipse? Even if the sun is under the horizon, the occurrence of atmospheric refraction helps us to view the sun. Atmospheric refraction allows us to glimpse a solar eclipse also. So the question now is, when is totality a possibility?
The answer: ahead of an actual sunrise that you can see or after an actual sunset you can also see, but only in a specific location. Even near totality, or in other words, a partial eclipse, has the same requirements. The sky takes on a darkened hue when a total or partial eclipse occurs, even more so than it would right before the sun rises or after setting.
Also, during total or partial eclipses, one may be able to view a substance close to where the sun is rising or setting. It could be a planet, usually Mercury. It would not be possible to see it without either eclipse.
The Saros Period
Lunations occur every 177 days, in which brief cycles of eclipses reiterate. These temporary cycles are referred to as sets and they persist for three to four years. Where the moon’s orbit rises or falls is where it all happens. If the rise or descent of the moon’s orbit misses the earth, the cycle of eclipses stops, that is the moon’s shadow intersecting with earth close to the north or south pole ends. Every 18 years, there are 5 distinctive sets, and this is called the Saros period.
The Effect of Movement
The moon eclipsing the sun causes the solar corona to become visible. The corona is not as dense as the sun, so it’s only visible when the sun is shielded. An initial photograph that was pretty transparent was taken by Bernard Leon Foucault with physicist Armand Fizeau in 1845.
But there seems to be an enigma regarding a solar eclipse and its consequence on the Focault pendulum, which is an uncomplicated pendulum hanging from an extended wire and placed in motion along a meridian. The motion stratum looks like it is turning clockwise in the Southern Hemisphere and counterclockwise in the Northern Hemisphere, which reveals an axial rotation of the earth.
In 1954 and 1959, Maurice Allais expounded that the Focault pendulum showed strange movements that could not be explained when a solar eclipse occurs. Questions surfaced surrounding whether his hypothesis is true. However, since the movements he hypothesized about did not fall under the Focault phenomenon, they were termed the Allais effect. Additionally, other changes were said to occur when the torsion pendulum moved. These movements are called the Saxl effect.
The rotational rate of the earth causes the length of the day to extend by 2.3 milliseconds per century. It seems small, but over the long term its effects are quite consequential. Each century, the earth gets behind about 40 seconds in its rotational rate. In a millennium, that time increases to 1 hour. Delta-T is the quantity used to define the time difference. Uniformly, the rotational rate.
Several phenomena get in the way of predicting the precise value of delta-T, both in the past and for the future. These are climatic non-tidal effects such as global warming, polar ice caps and ocean depths.
Also, there is no clear pattern or fundamental formula that exists to determine when an eclipse will occur or even tell when a subsequent solar eclipse will take place in the same geographical location. The odds of knowing when eclipses will occur is like tossing a coin. Maybe soon, more precise plotting will be developed to forecast the actual month, year and distinct geographical location.