Earth and Moon NotesEarth and Moon Notes

Rotation vs. RevolutionRotation vs. Revolution• Rotation- spinning of

earth on its own axis:• 24 hours = 1 day = 1

rotation• What causes night and

day.

RevolutionRevolution• Earth’s movement around the sun is a

revolution.• One complete revolution = 1 year = 365.25

days.

The SeasonsThe Seasons• Equator does not

experiences difference in temp. and daylight in seasons b/c 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 Northern HemisphereJune in 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 December in the Northern HemisphereHemisphere

• Earth’s axis pointed away from the sun.

• Winter = shorter days, colder temperatures, due to less direct sunlight and fewer hours of daylight.

June and December SolsticeJune and December Solstice• June 21st = longest day

of the year, considered first day of summer.

• December 21st, shortest day of the year, considered first day of winter.

Equinox in March and SeptemberEquinox in March and September• 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.

Gravity and MotionGravity 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 MotionGravity 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 MotionInertia 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 it’s inertia.

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

The MoonThe Moon

• The positions of the moon, Earth, and sun causes the phases of the moon, eclipses, and tides.

Rotation vs. RevolutionRotation vs. Revolution• A “day” and a

“year” are the same length on the moon.

• One day = 1 rotation of the moon= 29.5 earth days

Dark Side of the MoonDark Side of the Moon• The ‘dark side’ is

the side we never see.

• The moons whole set of phases occurs in 29.5 days

Phases of the moonPhases of the moon• Depends on

how much of the sunlit side of the moon faces the Earth

Eclipses occur when….Eclipses occur when….

• The moons shadow hits Earth or Earth’s shadow hits the moon

• There are ‘solar’ eclipses, and ‘lunar’ eclipses

Solar EclipseSolar Eclipse• Occurs when the moons shadow falls on the Earth. • Sun, moon and Earth aligned

• Lunar eclipses occur when the earth’s shadow falls on the moon

View of Solar EclipseView of Solar Eclipse

TidesTides• The tides are caused mainly by differences in how

much the moon’s gravity pulls on different parts of the Earth

High vs. Low TideHigh vs. Low Tide• Tides occur in a daily cycle. • As the Earth rotates on its axis, any point on

Earth goes through a cycle of high tide, low tide, high tide, low tide.

• The moon’s gravity causes high tide on the side closest to the moon,

• Low tide occurs when that part of the Earth is at a 90 degree angle to the moon.

• Tide Schedule