Eclipses result from the interplay of the rhythms of the Earth, the Moon, and the Sun. Because these rhythms do not align perfectly, eclipses are surprising events.
The plane of the Moon’s orbit is inclined about 5 degrees relative to the ecliptic (the plane of the Earth’s orbit around the Sun.) Therefore, during a new moon—when the Moon moves between the Earth and Sun—the Moon’s shadow usually passes either above or below the Earth. The Moon intersects the plane formed by the Earth and the Sun at two points in its orbit called the “nodes.” Like a fish leaping out of the water, the Moon rises above the ecliptic at the ascending node and plunges back below the ecliptic at the opposite descending node. Only if the new moon occurs when the Moon is at a nodal point does its shadow fall on Earth. Thus, the new moon phase and the Moon’s position at the node must coincide for a solar eclipse to occur during which, from Earth, we see the Moon cover the Sun.
It’s a bit more nuanced than that: Because the Earth is larger than the Moon’s umbra (the deepest part of its shadow), the Moon does not have to be exactly at the node. It can be up to 12 degrees along its orbit before or after the node. These 12 degrees happen to represent the range of the Moon’s movement along its orbit in a day. This means that the Moon’s passage through its node and the new moon must occur within one day of each other for a total solar eclipse to occur.
For the upcoming solar eclipse, the new moon occurs on August 12 and the Moon reaches its descending node 16 hours later, on August 13 [in Europe.] At the time of the new moon the Moon is thus still above the ecliptic, so the Moon’s umbra strikes the Earth at northern latitudes. It will be 18 years, 11 days, and 8 hours, before similar conditions will occur again—when the new moon and the Moon’s passage through its node (the draconic month) will coincide once more in this position.
As with all cosmic alignments, no two rhythms coincide exactly. There’s a small gap—musically speaking, a beat. There are 223 new moon positions in 6,585.32 days, and 242 lunar node transits in 6,585.36 days. The difference is 0.04 days, or one hour. This means that every time a new moon and a node passage coincide, the node is reached one hour later. Consequently, at each new moon, the Moon is slightly higher in the sky. So, with each subsequent eclipse, the eclipse path shifts correspondingly farther north across the Earth until it eventually only grazes the Earth as a partial eclipse.
In the 17th century, the astronomer Edmond Halley studied these 18 year-11 day-8 hour cycles. He called them “Saros Cycles” based on Babylonian terminology, as this pattern was already known in ancient times. There are roughly 42 different Saros Cycles running in parallel which result in approximately 63 total solar eclipses per century.
Left: During a solar eclipse, a distinction is made between the Moon’s umbra and penumbra. If you are located where the Moon’s umbra reaches Earth, you will see the entire disk of the Sun covered by the Moon. If you are located where the penumbra reaches Earth, you will still see a crescent of the Sun. Interesting fact: even if you can see only one percent of the Sun, it’s still quite bright. A minuscule amount of sunlight is enough to create the impression of “daytime” on Earth.
Center: If you are within the path of totality, it gets so dark for two minutes that you can see the planets and bright stars during the day. This map shows what can be seen for the upcoming eclipse: Mercury and Jupiter shine to the right below the darkened sun, and Venus to the left above it. A reddish hue is visible across the entire horizon, similar to that of a sunset. The night-blue of the sky is just as enigmatic as the mustard-colored hue in the landscape. Towering above it all is the Sun’s corona. It consists of infinitely fine veils that remind us of what is otherwise invisible: the Sun’s periphery, whose solar wind encompasses the entire solar system as its interior.
Right: The illustration shows the percentage of the Sun that is obscured, depending on the observation location. Further east, the shadow ends because the Sun will have already set there. Barcelona, for example, is just outside the path of totality. From a Swiss perspective, about 90 percent of the Sun will be obscured, and in Germany, between 82 and 90 percent. The further east you are, the lower the Sun will be on the horizon.
The Sun’s Night Journey
On August 2, 2027, another total solar eclipse will occur in Spain and Egypt. With a duration of over 6 minutes, this eclipse will be the longest of the 21st century. It will hold another mystery: the peak of this solar eclipse will occur right near Luxor, Egypt. There, in the burial chambers of the Valley of the Kings, lies the comprehensive record of Egyptian solar theology. In his book Die Nachtfahrt der Sonne [The night journey of the Sun],1 egyptologist Erik Hornung deciphered this infinitely complex description of the sun’s fate during the night.
Significantly, during this remarkable solar eclipse on August 2, 2027, the astronomical night journey of the sun will complement the spiritual night journey of the sun in Egyptian solar doctrine. This eclipse is part of Saros Cycle No. 136, which—after another three cycles of 18 years, 11 days, and 8 hours—will pass over Switzerland and southern Germany on September 3, 2081. For Switzerland, it has been a long wait: the moon’s shadow last swept across this Alpine country in 1724.
Illustrations taken from Wolfgang Held, Sternkalender Ostern 2026 bis Ostern 2027. Die totale Sonnenfinsternis im Jahr des Löwen [Star Calendar: Easter 2026 to Easter 2027. The total solar eclipse in the year of the lion.] Verlag am Goetheanum, Dornach 2025.
Translation Laura Liska
Title image The foliage of a tree provides thousands of lenses through which the sunlight is refracted. The street becomes a canvas for these crescents of the eclipsed sun.
