The Earth in Space

The Earth’s Gravity ► – force of attraction between all matter. ► Gravity – force of attraction between all matter. ► – the force between two objects depends upon their masses and the distance between them ► Law of Gravitation – the force between two objects depends upon their masses and the distance between them Isaac Newton

► Are weight and mass the same?  No! ► Mass = the amount of matter in an object ► Weight = strength of the pull of gravity ► Weight is measured in NEWTONS ► Weight depends on:  An object’s mass and  The object’s distance from the Earth’s center

► Knowing this, and that the Earth’s true shape is an oblate spheroid, where on Earth would you weigh the MOST…at the Poles or at the Equator?

.3% more at the POLES

Movements of the Earth A. Rotation – the spinning of Earth on its axis  This takes 24 hours

B. Revolution ► Earth’s orbit around the sun. ► This takes days  – Earth is the closest to the sun (January 3 rd )  Perihelion – Earth is the closest to the sun (January 3 rd )  – Earth is the furthest AWAY from the  Aphelion – Earth is the furthest AWAY from the sun (July 4 th ) sun (July 4 th )

► ► What causes Earth’s seasons?

The Seasons 1. Summer Solstice – first day of summer (in the Northern Hemisphere)!  June 21st or 22 nd  Northern hemisphere is tilted TOWARDS the sun  Sun’s rays are directly over the Tropic of Cancer  24 hours of sun at the Arctic Circle  24 hours of darkness at the Antarctic Circle

2. Winter Solstice – first day of winter (in the Northern Hemisphere)  December 21st or 22 nd  Northern Hemisphere is tilted AWAY from the sun  Sun’s rays are directly over Tropic of Capricorn

3. Autumnal Equinox  September 21st or 22nd  Sun is directly over the Equator  Equinox – EQUAL day and night everywhere

4. Vernal Equinox  March 21st or 22 nd  Sun is directly over the Equator  Equinox – EQUAL day and night everywhere