THE MOON

The Moon formed about 4 billion years ago, when another small planet hit Earth. The collision destroyed the smaller planet, and broke off pieces of Earth. The pieces were thrown into space, forming a ring around the damaged Earth The ring debris eventually came together to form the Moon.

After the collision, the moon was very close to Earth but has since drifted over 260,000 miles away.

Sidereal Month time to complete one full orbit of Earth = true orbital period = 27.3 days.

Lunar Month time to complete one cycle of phases (i.e. full moon to full moon) = ~ 29.5 days. Our monthly calendar is based on this

27.3 days +2.2 days Lunar Month – 29.5 days =29.5 days

Opposition- That time during the moon's orbit when the moon is on the opposite side of Earth from the sun.

Conjunction- time during the moon's orbit when the moon is on the same side of Earth as the sun..

Gravitational Lock Due to gravity, the moon’s rotation equals the moon’s orbital period around Earth Resulting in the same side of the moon always facing Earth Several other moons in the solar system also exhibit it

Phases of the Moon caused by sunlight on moon as seen from Earth

New Moon

Waxing Crescent Moon

1st Quarter Moon

Waxing Gibbous Moon

Full Moon

Waning Gibbous Moon

3 rd Quarter Moon

Waning Crescent Moon

New Moon

SOLAR ECLIPSE The moon comes between Earth and sun, blocking the sun TOTAL SOLAR ECLIPSE - moon blocks all of the sun Partial SOLAR ECLIPSE – a corner of the sun peaks through Annular SOLAR ECLIPSE – moon doesn’t quite cover the sun

Total Eclipse

The moon actually casts its shadow on Earth

How does it work? Eclipses are rare coincidence. The size of the moon as seen in space, is almost exactly the size of the sun as seen in space. Thus, the moon’s disk is almost a perfect fit in front of the sun’s disk. There is a slight difference, so the moon does block out the sun’s disk for a few minutes.

Umbra Penumbra There are two distinct shadows … the Umbra and Penumbra

Umbra Penumbra The Umbra is the tiny inner shadow. Here, the sun is totally blocked and it gets dark outside – a total eclipse.

Umbra Penumbra The Penumbra is the big outer shadow. Here, the sun is partially blocked out. It is like a cloudy day out – a partial eclipse.

A starry Night Pro Demo of solar eclipses

Earth comes between the moon and the sun, blocking the moon TOTAL LUNAR ECLIPSE - Earth blocks all of the sun from hitting the moon PARTIAL LUNAR ECLIPSE - a bit of the sun still shines on the moon Lunar Eclipse

The Earth casts its shadow on the moon

Umbra Penumbra There are also two distinct shadows the Umbra and Penumbra

During a lunar total eclipse, the moon may turn blood red

The Earth’s shadow is large. When the moon enters it, a total eclipse can last for almost an hour

A Starry Night Pro Demo of lunar eclipses

Solar Eclipse – Relative positions of sun, earth and moon New moon

Lunar Eclipse – Relative positions of sun, earth and moon full moon

Tides Tides are changes in ocean height, due to the gravity of the Moon High Tide Opposing High Tide Low Tide

There are two high and two low tides per day High Tide Opposing High Tide Low Tide

The typical high tide bulge is about 6- 8 ft. on the moon side 6’ – 8’ High Tide Opposing High Tide Low Tide

Spring Tide - a 10’ high tide caused by moon and Sun both lined up and pulling on Earth - once/month 10’ Spring High Tide

Neap Tide - a 4’ high tide caused by moon and Sun pulling on Earth at right angles - occurs twice/month 4’ Neap High Tide