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The Earth’s precession is a slow, cyclical motion of the rotational axis that causes the position of the celestial poles to change over time. This motion is caused by the gravitational influence of the Moon and Sun on the Earth’s equatorial bulge, and it has a period of about 26,000 years.

Over astronomical time, the Earth’s precession has caused a number of changes in the position of the stars and constellations in the sky. For example, due to precession, the position of the North Star, or Polaris, has shifted over time, and in ancient times, other stars, such as Thuban, were used as celestial markers for navigation. Additionally, precession can cause changes in the length and timing of the seasons over long timescales.

The Earth’s precession is affected by a number of factors, including the gravitational pull of other planets, the shape of the Earth’s orbit around the Sun, and the distribution of mass within the Earth itself. These factors can cause slight variations in the rate and direction of precession over time.

Overall, while the effects of precession on the Earth’s rotation and position in the sky are not easily observable on human timescales, they are an important component of the Earth’s long-term astronomical behavior.

Gallery: Other Ways of Knowing Climate Change