Watch: Earth’s Wobble Creates a Twilight Zone Shadow

A daily photo taken from September 2023 to September 2024 offers an intriguing view of the twilight zone transition caused by the Earth’s 23.5-degree axial tilt during its orbit around the Sun.

Without the Earth’s axial tilt, we wouldn’t experience seasonal changes, and the length of the day would remain constant throughout the year. Instead, we have two equinoxes annually—one in March and one in September—when the Sun is positioned directly above the equator, resulting in nearly equal day and night lengths across the globe.

Winter Solstice and Polar Night in the Northern Hemisphere

In the Northern Hemisphere, the winter solstice occurs three months after the September equinox, when the North Pole is tilted maximally away from the Sun, resulting in the least sunlight received each day and the longest night for those in the north. During this period, regions near the North Pole can experience weeks where the Sun does not rise above the horizon, a phenomenon known as Polar Night.

(Quick editor’s note: The Tweet above states December 2023-September 2024, but it should say September 2023-September 2024.)

The summer solstice in June for the Northern Hemisphere is the exact opposite, as the Earth leans toward the Sun. In areas near the Arctic Circle, such as northern Alaska or Norway, a phenomenon known as the Midnight Sun occurs, where the Sun remains above the horizon and follows an elliptical path across the sky without setting. The further north you go, the higher the Sun will appear during this prolonged daylight. At the North Pole, the Sun does not set for six months, continuously looping around the sky.

The Earth’s Rotational Wobble and Its Impact on Solstices and Equinoxes

The Earth’s rotational axis is not perfectly stable; it has a slight wobble with a cycle of about 26,000 years. This wobble causes the dates of solstices and equinoxes to shift gradually over centuries before returning to their original positions.

Ancient civilizations were aware of the Earth’s rotation around the Sun. Stonehenge, whose builders and construction date remain uncertain, aligns perfectly with the sunrise on the summer solstice.

Similarly, the Great Sphinx of Egypt, constructed around 5,000 years ago, faces the rising Sun during the spring (vernal) and autumn equinoxes. In ancient Egyptian culture, the primary deity was Ra, the sun god, revered as the creator of all things.

El Castillo, built nearly 2,000 years ago by the Mayans in the Yucatán Peninsula, exemplifies their advanced calendrical knowledge. This pyramid was designed so that, during the spring and autumn equinoxes, sunlight casts shadows along its staircases, creating the illusion of Kukulcán, the “Serpent of Light,” descending to meet the stone-carved head at the base. This level of precision is impressive, considering the Mayans utilized multiple calendars, including one—Haab’—that had 365 days, similar to our modern Gregorian calendar.

Observing a time-lapse of the Earth from a geostationary perspective is fascinating, but witnessing it from the International Space Station is equally remarkable.

Read the original article on: New Atlas

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