The Moon(Earth’s natural satellite)

Phases, Eclipses & Tides

Vocabulary

satellite lunar phase eclipse lunar eclipse solar eclipse umbra penumbra tide spring tide neap tide

Formation of the Moon

Scientists think that the Moon formed when another large object collided with Earth.

A large amount of matter was ejected into space in the collision.

Formation of the Moon (cont’d)

The material eventually formed the Moon.

Motion of the Moon

Gravitational force between Earth and the Moon causes the Moon to orbit the Earth.

The “near side” of the moon always faces Earth, the “far side” always faces away.

Motion of the Moon (cont’d)

The moon rotates on its own axis once every 28*

days. Because the moon also revolves around Earth every 28 days, a “day” and a “year” on the moon are the same length.

*anywhere from 27.3 to 29.5 days.

Motion of the Moon (cont’d)

Phases of the Moon

The sun is shining from the right. The outside ring of photos shows the different amounts of the sunlit side of the moon that an observer on Earth sees as the moon revolves around Earth.

Phases of the Moon (cont’d)

Phases are caused by changes in the relative positions of the moon, Earth and the sun.

The phase of the moon you see depends on how much of the sunlit side of the moon faces Earth.

Phases of the Moon (cont’d)

As the moon revolves around Earth, you see more and more of the lighted side of the moon every day, until the side of the moon you see is fully lit.

As the moon continues in its orbit, you see less and less of the lighted side of the moon. About 29.5 days after the last new moon, the cycle is complete, and you see a new moon again.

Eclipses

An eclipse occurs when an object in space comes between the sun and a third object, and casts a shadow on that object.

There are two types of eclipses:solar eclipselunar eclipse

Solar Eclipse

A solar eclipse occurs when the moon passes between Earth and the sun, blocking the sunlight from reaching Earth.

This can only occur during a new moon, but not every month because of the tilt of the moon’s orbit.

umbra

penumbra

Total Solar Eclipse

A Total Solar Eclipse is only experienced by the part of Earth that is in the umbra. Here the sky appears dark, you can see the stars and the solar corona.

corona

Partial Solar Eclipse

A partial solar eclipse is experienced by the part of the Earth in the penumbra.

Part of the sun remains visible.

Lunar Eclipse

A lunar eclipse occurs at a full moon when Earth is directly between the moon and the sun.

umbra

penumbra

Total Lunar Eclipse

A total lunar eclipse occurs when the moon is completely in Earth’s umbra.

It can be seen anywhere on Earth that the moon is visible.

Partial Lunar Eclipse

A partial lunar eclipse occurs when the moon passes partly into the umbra of Earth’s shadow.

The edge of the umbra appears blurry, and you can watch it pass across the moon for two or three hours.

Tides

Tides are the rise and fall of water, every 12.5 hours or so.

Tides occur mainly because of differences in how much the moon pulls on different parts of Earth.

High tides occur at the point on Earth closest to the moon and on the exact opposite side of Earth. Low tides are in between.

Spring Tide vs. Neap Tide

Spring tide occurs when the sun, Earth and moon are in nearly a straight line. (During the new moon)

The gravity of the sun and moon pull in the same direction.

The combined forces produce the greatest difference between high and low tide.

Spring Tide vs. Neap Tide (cont’d)

Neap tides occur when the line between Earth, sun and moon are in a right angle. (During the moon’s 1st & 3rd quarter.)

This produces a tide with the least difference between low and high tide.