Earth Notes Chapter 12

Rotation vs. Revolution Rotation- spinning of earth on its own axis: 24 hours = 1 day = 1 rotation The Earth’s rotation causes night and day.

Revolution Earth’s movement around the sun is a revolution. 1 complete revolution = 1 year = 365.25 days

The Seasons Equator does not experiences difference in temp. and daylight in seasons because it receives the most direct sunlight. Poles = extreme temp. differences. Winter in Alaska = 2 hrs of daylight, in summer = sun never sets. Seasons caused by the tilt of the Earths axis – tilted 23.5 degrees

June in the Northern Hemisphere Axis tilted towards the sun. Summer – longer days, warmer temperatures NOT caused by the distance from the sun, caused by more direct sunlight.

December in the Northern Hemisphere Earth’s axis pointed away from the sun. Winter = shorter days, colder temperatures, due to less direct sunlight and fewer hours of daylight.

Misconception Seasonal differences are NOT caused by changes in the distance from the sun. They are caused by changes in the amount of direct sunlight due to the 23.3* tilt of Earth’s axis.

June and December Solstice June 21st = Summer Solstice Longest day of the year, considered first day of summer. December 21st = Winter Solstice Shortest day of the year, considered first day of winter.

March and September Equinox Equinox is halfway between each solstice. Equinox – neither hemisphere is pointed towards or away from the sun. Equinox (equal night) 12 hrs day/12 hrs night March 21st – spring equinox, September 22nd – fall equinox.

BRAINPOP

Gravity and Motion Recall that gravity is a force that attracts all objects towards each other. Universal Law of Gravitation – every object in the universe attracts every other object.

Gravity and Motion The strength of gravity is dependent on 2 things: the mass of the objects, and the distance between them. If mass increases, gravity increases. If distance increases, gravity decreases. Weight – the force of gravity on an objects mass.

Inertia and Orbital Motion Two factors keep Earth and the moon in their orbits – inertia and gravity. Earth’s gravity pulls the moon toward it, preventing the moon from traveling in a straight line. The moon keeps moving ahead because of its inertia.

Inertia Inertia is the tendency of an object to resist a change in motion.