The Earth in SpaceThe Earth in Space

The Earth’s GravityThe Earth’s Gravity

►Gravity – force of – force of attraction between attraction between all matter.all matter.

►Law of Gravitation – the force between – the force between two objects depends two objects depends upon their masses upon their masses and the distance and the distance between thembetween them

Isaac Newton

►Are weight and mass the same?Are weight and mass the same? No! No!

►Mass = the amount of matter in an objectMass = the amount of matter in an object►Weight = strength of the pull of gravityWeight = strength of the pull of gravity

►Weight is measured in NEWTONSWeight is measured in NEWTONS►Weight depends on:Weight depends on:

An object’s mass andAn object’s mass and The object’s distance from the Earth’s centerThe object’s distance from the Earth’s center

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

.3% more at the POLES

Movements of the EarthMovements of the Earth

A. A. RotationRotation – the spinning of – the spinning of Earth on its axisEarth on its axis This takes This takes 2424 hours hours

B. B. RevolutionRevolution ►Earth’s orbit around the sun.Earth’s orbit around the sun.►This takes 365.25 daysThis takes 365.25 days

Perihelion – Earth is the closest to – Earth is the closest to the sun (January 3the sun (January 3rdrd))

Aphelion – Earth is the furthest – Earth is the furthest AWAY from the AWAY from the

sun (July 4sun (July 4thth))

►What causes Earth’s seasons?

The SeasonsThe Seasons

1. 1. Summer Solstice Summer Solstice – first day of – first day of summer (in the Northern Hemisphere)! summer (in the Northern Hemisphere)! June 21st or 22June 21st or 22ndnd

Northern hemisphere is tilted Northern hemisphere is tilted TOWARDS the sunTOWARDS the sun

Sun’s rays are directly over the Sun’s rays are directly over the Tropic of CancerTropic of Cancer

24 hours of sun at the Arctic Circle24 hours of sun at the Arctic Circle 24 hours of darkness at the Antarctic 24 hours of darkness at the Antarctic

CircleCircle

2. 2. Winter Solstice Winter Solstice – first day of – first day of winter (in the Northern winter (in the Northern Hemisphere)Hemisphere) December 21st or 22December 21st or 22ndnd

Northern Hemisphere is tilted Northern Hemisphere is tilted AWAY from the sunAWAY from the sun

Sun’s rays are directly over Tropic Sun’s rays are directly over Tropic of Capricornof Capricorn

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

everywhereeverywhere

4. 4. Vernal EquinoxVernal Equinox March 21st or 22March 21st or 22ndnd

Sun is directly over the EquatorSun is directly over the Equator Equinox – EQUAL day and night Equinox – EQUAL day and night

everywhereeverywhere