In his article “Earth’s Wobble Wreaks Havoc on Astronomers—and Astrologers, Too” in the January 12, 2024 issue of
ScientificAmerican.com, professional astronomer and science communicator Phil Plait explains that the Earth has two major motions in and through space—the daily spin it makes around its axis
(diurnal rotation) and its yearly orbit around the Sun
(annual revolution). Other than this, he says, the Earth goes through a third little-known motion called
precession that makes it slightly wobble upon its rotational axis.
IMAGE CREDIT: CLIMATE.NASA.GOVAltogether, the centrifugal force of the Earth’s spin makes its equator bulge, the Sun’s gravity pulls on that misaligned bulge, and the gravity of the Moon that’s orbiting the Earth yanks on that bulge as well. The outcome is that the direction of Earth’s axis slowly wobbles in space, making a complete circle once every 26,000 years or so.
“While the [Earth’s] wobble is pretty big, it takes a long time to play out,” astronomer Plait says. “Over a human lifetime, the effect is so small as to be unnoticeable. But over humanity’s lifetime, the effect has been not only noticeable but profound. Earth’s wobble has affected climate, navigation and our calendar. It’s even had an impact on pop music.”
Plait then dwells in some detail on the impact of this wobble on astronomy and astrology as well as on history and literature.
Read in full Phil Plait’s “Earth’s Wobble Wreaks Havoc on Astronomers—And Astrologers, Too” in ScientificAmerican.com now!
