THE MOON

Definitions•Year – time that a planet takes to

go around the sun once.•Revolution – motion of a body

orbiting another body in space•Prograde rotation –

counterclockwise spin of a planet or moon as seen from above the planet’s North Pole (rotates in the same directions as the sun’s rotation), EARTH

• Retrograde rotation – the clockwise spin of a planet or moon as seen from above the planet’s North Pole. Venus, Uranus

• Greenhouse effect – carbon dioxide traps thermal energy from sunlight, causes surface temperatures to increase

• Gas Giants – planets that have deep, massive atmospheres rather than hard rocky surfaces like those of the inner planets

• Satellites – natural or artificial bodies that revolve around larger bodies such as planets. All planets, except MERCURY and VENUS have satellites.

• Phases – change in the sunlit area of one celestial body as seen from another celestial body.

• Eclipse – an event in which the shadow of one celestial body falls on another

Measuring Distance in Space

•Astronomical Unit – the average distance between the Earth and the Sun

• Using the speed of light – light travels at about 300,000 km/s in space

• In 1 second, light travels 300,000 km.• In 1 minute, light travels nearly

18,000,000 km – LIGHT MINUTE• 1 AU = 8.3 light minutes

Astronomical Unit – the average distance between the

Earth and the Sun

Solar System Divided into two main parts

•Inner solar system contains four planets that are closest to the sun (Mercury, Venus, Earth and Mars)

•More closely spaced•Terrestrial planets•Dense and rocky

Inner Planets

•Outer system contains 4 planets farthest from the sun. (Jupiter, Saturn, Uranus, Neptune)

•Composed mostly of gas•GAS GIANTS•Pluto is now considered a

satellite of Neptune – It’s not composed of gas – is small, dense and rocky

The Outer Planets

Why did the Earth have such good fortune?

• It’s just at the right distance from the Sun

• Warm enough to keep most of its water from freezing

• Cool enough to keep its water from boiling away

• Liquid water is a vital part – all living things depend on

The surface of bodies that have no atmosphere preserve a record of almost all of the impacts that the bodies have had.

LUNAR ORIGIN 3 possible explanations for the

moon’s formation:1. Moon was a separate body

captured by Earth’s gravity2. Moon formed at the same time

and from the same materials as the Earth

3. The newly formed Earth was spinning so fast that a piece flew off and became the moon

• When a moon rock was brought back, scientist found that the composition of moon was similar to that of the Earth’s mantle.

•CURRENT THEORY – large, Mars-sized object collided with Earth while Earth was still forming. Collision was so violent that part of the Earth’s mantle was blasted into orbit around Earth to form the moon.

Origin of the moon

IMPACT

EJECTION

FORMATION

Basic Moon Stats• 384,000 Km away• 3476 km in

diameter(1/4 of

Earth)• Density 3.3 g/cc• Mass is 1/80 of

Earth• Gravity is 1/6 of

Earth

Basic Moon Stats •Temp varies from -175 C to

100 C!!!•Age is similar to Earth•No Atmosphere or water•Revolves once every 27.3 days•Rotates once every 27.3 days•Blue Moon – 2 full moons in

one month (1)

Exploration of the Moon

• Apollo Moon Landing Project

• Neil Armstrong walked on moon in 1969

• Ended in 1972• Humans

haven’t been back since

• Perigee-moon is closest to Earth• Apogee-moon is furthest from

Earth

Perigee Apogee356410 km 406700 km

5% Variation in distance from Earth!

PHASES OF THE MOON

•The different phases are due to its changing position

•WAXING – sunlit fraction that we see is getting BIGGER (lit on the RIGHT)

•WANING – sunlit fraction that we see is getting SMALLER (lit on the LEFT)

PHASES OF THE MOON

PHASES OF THE MOON•Total amount of sunlight that the

moon gets remains the same – Half the moon is always in sunlight

•Because the moon’s period of rotation is the same as its period of revolution – on Earth you always see the same side of the moon

PHASES OF THE MOON

Does the Moon Rotate?•We always see

the same side of the Moon – it’s rotation and revolution are equal

•Synchronous Rotation

The Moon and The Tides

Neap Tide

• Neap Tide-A weaker than average tide due to the conflicting gravitational forces of the sun and moon

Spring Tide

• Spring Tide-A stronger than average tide due to the gravitational forces of the sun and moon working together (3)

ECLIPSES

• When the shadow of one celestial body falls on another, an eclipse occurs.

SOLAR ECLIPSE

•SOLAR ECLIPSE – happens when the moon comes between Earth and the sun and the SHADOW OF THE MOON FALLS ON PART OF THE EARTH

•Only occurs during NEW MOON PHASE

SOLAR ECLIPSE - we see some portion of the Sun's disk

covered or 'eclipsed' by the Moon.

Solar Eclipse

Solar Eclipse

•During a total solar eclipse, the disk of the moon completely covers the disk of the sun.

Total Solar Eclipse

LUNAR ECLIPSE

• Happens when earth comes between the sun and the moon and THE SHADOW OF EARTH FALLS ON THE MOON

• Only occurs during FULL MOON PHASE

•Because the moon’s orbit is elliptical, the distance between the moon and the Earth changes

Lunar Eclipse

The shadow of the Earth falls on the moonThe shadow of the Earth falls on the moon

Which gives the moon a Which gives the moon a reddish tintreddish tint

Lunar Eclipse

Annular Eclipse – type of solar eclipse

•During an annular eclipse, the disk of the moon does not completely cover the sun

•During a total solar eclipse the disk of the moon does completely cover the sun – only the corona is visible

annular eclipse

Total Solar Eclipse

Orbit of the Moon

•The moon’s orbit around Earth is tilted about 5º relative to the orbit of Earth.

•This is why there aren’t solar and lunar eclipses every month

Tilt of the Moon’s Orbit

•Tilt is enough to place the moon out of Earth’s shadow for most full moons and Earth out of the moon’s shadow for most new moons.