What term describes the wobble of Earth's rotation axis?

What term describes the wobble of Earth's rotation axis?

• A. Precession (wobble of Earth)
• B. Obliquity
• C. Nutation
• D. Ecliptic

Answer: (A)

The wobble of Earth's rotation axis is called precession. It’s the slow, conical motion of where the axis points in the sky, driven by gravitational torques from the Moon and the Sun on Earth's equatorial bulge. This causes the axis to sweep a circle in space over about 26,000 years, so the specific star aligned with the pole changes over millennia. There is also a smaller, quicker wobble called nutation, which rides on top of precession and is due to the Moon’s orbit and other orbital factors, but it’s the long-term, steady precession that best describes the wobble in question. Obliquity is the tilt angle itself, and the ecliptic is the Sun’s apparent path through the sky.

The wobble of Earth's rotation axis is called precession. It’s the slow, conical motion of where the axis points in the sky, driven by gravitational torques from the Moon and the Sun on Earth's equatorial bulge. This causes the axis to sweep a circle in space over about 26,000 years, so the specific star aligned with the pole changes over millennia.

There is also a smaller, quicker wobble called nutation, which rides on top of precession and is due to the Moon’s orbit and other orbital factors, but it’s the long-term, steady precession that best describes the wobble in question. Obliquity is the tilt angle itself, and the ecliptic is the Sun’s apparent path through the sky.