5.7 Earth’s Motion and the Atmosphere

As you should know… The Earth rotates around its geologic axis.

It also revolves around the Sun.

The Earth - along with the rest of our Solar System - revolves around the center of our Milky Way galaxy.

The Solar System with Earth, of course, also moves with the galaxy out from the original point of the Big Bang.

The Earth also precesses!

Precession The direction that the Earth’s north axis points to changes gradually in a circle every 26,000 years.

It precesses like a top.

It takes about 26,000 years to make one rotation. Currently the North Pole points toward Polaris. In 14,000 AD it will point to Vega! (It pointed to Thuban in 3,000 BC.)

Remember Earth’s Rotation… All parts rotate once in 23 hrs 56 min, but the Tangential Velocity varies with latitude. It is about… •1000 mph at the Equator. •800 mph here in Culver City. •0 mph at the Poles.

The Coriolis Effect Due to Earth’s rotation, an object trying to go directly from Pole to Equator will be deflected to the West. One going from Equator to Pole will be deflected East.

Ocean Currents to circle clockwise in the Northern Hemisphere, and counterclockwise in the Southern.

Storms circle counterclockwise in the Northern Hemisphere, and clockwise in the Southern.

This storm is circling counter-clockwise This storm is circling counter-clockwise. Is it occuring in the Northern Hemisphere or the Southern?

Atmospheric convection currents are deflected into prevailing winds, which divide the atmosphere into bands moving in alternate directions.

Jupiter has many opposing wind bands, with jet streams between them.