​Objectives

- identify the difference between rotation and revolution

- explain how the tilt in Earth's axis causes the seasons

​Speeding Through Space

Everything in the universe moves!

Earth travels 584 million miles per year. It moves 66,637 miles per hour.

Earth also spins - 1037 mph at the equator and 0 mph at the poles.

Rotation

Rotation - Earth spins on an axis (an imaginary line running through the poles). This is why we have day and night.

Earth's rotation causes day and night and the shape of the planet.

Revolution

Revolution - the Earth's movement around the sun. This is why we have seasons.

As Earth orbits the sun, the direction in which Earth's axis points changes. This is why the Northern and Southern hemispheres experience opposite seasons.

Solstices and Equinoxes

Summer solstice - greatest number of daylight hours

Winter solstice - fewest number of daylight hours

Spring & Autumnal equinoxes - same number of daylight and nighttime hours

These happen the same time every year.

Predicting the Seasons

In ancient societies, predicting the seasons was a matter of survival, and some people learned that most constellations could only be viewed during certain seasons.

They built earthen, wooden, and stone devices that aligned with the Sun and stars. These acted as calendars.

The Tilting Planets

The way the Earth is tilted on its axis creates the seasons. Summers are more extreme in the Southern Hemisphere because the Earth is closest to the Sun in January.

Great Job!

Today, you learned:

- about the difference between rotation and revolution;

- how the tilt in Earth's axis causes the seasons