Study Guide for Gravity, Day / Night, and Seasons
Gravity:
Mass: the amount of matter than an object has. Remains unchanged from place to place
Weight: an effect of the gravity on an object: will change from place to place
Gravity: an attraction between two masses
Depends on two things: mass and distance
Mass:
the greater the mass b/t two objects the greater the gravity
Distance: the greater the distance b/t two objects the less the gravity
Minimum speed required to stay in orbit is 8000 m/s.
if you go much slower than this you will fall back to Earth: not enough inertia, too much gravity
if you go much faster than this you will leave Earth’s orbit: not enough gravity, too much inertia
Day / Night and Seasons:
Rotataion – Spinning of Earth on it’s axis – takes 24 hours = 1 day
The earth Rotates from the west to the east
Revolution – Earth moving around the sun – takes 364 ¼ days = 1 year
Spring Equinox –
● Time of year when day and night are of equal length.
● Date at which the axis is pointed neither towards nor away from the sun. March 21st.
Fall Equinox ● Time of year when day and night are of equal length.
● Date at which the axis is pointed neither towards nor away from the sun. September 23rd.
Summer Solstice –
● Time of year when the NH has its longest day.
● Date at which the northern hemisphere is pointed towards the sun. June 21st.
Winter Solstice –
● Time of year when the NH has its shortest day.
● Date at which the northern hemisphere is pointed away from the sun. December 21st
tilt- 23 ½ degrees
Axis – imaginary vertical line running through the center of the Earth around which the Earth rotates, or spins.
Tropic of Cancer:
● Located at 23.5 degrees north.
● On the summer solstice, direct rays of the sun strike this point.
Tropic of Capricorn:
● Located at 23.5 degrees south.
● On the winter solstice, direct rays of the sun strike this point.
Arctic Circle:
● located at 66.5 degrees north.
● On the summer solstice, any location above the arctic circle will experience 24 hours of daylight.
Antarctic Circle:
● located at 66.5 degrees south.
● On the winter solstice, any location above the arctic circle will experience 24 hours of daylight.