The Earth-Moon System

Spheres A sphere can be defined as a three dimensional figure like a ball – The Sun, all planets and moons are spheres

Ellipse An ellipse – very similar to a circle…a little oval shaped Each planet orbits the sun in an elliptical path During certain times of the year…the Earth is closer to the sun than other times of the year. Ellipse Animation

Rotation The planets, the Sun, moons, and the Earth all rotate around their axis, or center. All planets, except Venus and Uranus, rotate counter-clockwise

Revolution The orbit of one body around another…the Earth makes one revolution of the Sun in 365 days. The Moon makes one revolution of the Earth in 28 days All planets orbit the Sun in a counter-clockwise direction

Earth Moon Relationship Earth’s only natural satellite. Size scale – If the Earth was a basketball with a 12” diameter (1 foot) then the moon would be a 3” tennis ball. Distance scale – using the same scale as above – the moon would be 30 feet away. Correct size scale Incorrect distance scale

Other Moons of Importance Four of Jupiter’s many moons Called the Galilean moons (Galileo first found them) Io has a special characteristic…

Jupiter’s Io Only known moon to be volcanically active in the solar system

Saturn’s Many Moons Titan is heavily studied right now – has similarities to Earth

Earth’s Moon - Revolution & Rotation The moon orbits the Earth, roughly once every 28 days. (once a month) The moon spins on its axis once every 28 days. (once a month) Therefore, the rotation and the revolution are the same rate. Most moons in the solar system have the same tendency – phenomenon called tidal lock

The Dark Side of the Moon There actually is a “dark” side of the moon – at least as seen from Earth WE ONLY SEE ONE SIDE OF THE MOON BECAUSE IT ROTATES AND REVOLVES AT THE SAME RATE

Lunar Craters & Maria Mare – Greek for sea - Seas of lava The moon’s surface is covered with craters and maria. Impact craters – from the bombardment of meteors. Craters more visible than craters on Earth - no erosion or vegetative cover on the moon Maria - flat regions made by ancient lava flows. (no volcanic activity on the moon in millions of years) Crater abundance

Apollo Mission Landing Sites

Phases of the Moon Click below for video clip

Phases of the Moon

Phases of the Moon Moon phases are caused by the moon’s orbit around the Earth and its reflection of the sun Waxing indicates the portion of the moon’s surface we see is getting larger Waning indicates the portions of the moon’s surface we see is getting smaller

Phases of the Moon

Solar Eclipses A solar eclipse occurs when the Moon passes between the Sun and the Earth. Occurs during which moon phase? New moon During a solar eclipse the normally transparent corona (outer layer of the sun) can be seen.

Solar Eclipses

- Direct shadow – very small area - Secondary shadow – much larger area

Solar Eclipse

Lunar Eclipses Occurs during which moon phase? Full Occurs when the Moon passes into the shadow cast by the Earth Occurs during which moon phase? Full

Lunar Eclipse

Reason for the seasons What causes Winter, Spring, Summer & Fall?

What does this graph tell you?

What does this graph tell you? Earth’s path around the sun is not a perfect circle The path is in the shape of an ellipse Earth is closer to the sun in January (winter in the northern hemisphere) Distance to the sun has NOTHING to do with Earth’s seasons

What causes Earth’s Seasons? Click below for video clip

The Earth’s Tilt The Earth is tilted on its axis 23.5 degrees. The Earth’s tilt is the reason why we experience different seasons on Earth. As the Earth travels around the sun throughout the year, different parts of the Earth are tilted toward the direct rays of the sun.

Equinox and Solstice Vernal (spring) or autumnal (fall) equinox = equal day and equal night. Winter solstice = shortest day of the year in the NH Summer solstice = longest day of the year in the NH