Question

How are tides, moon phases and eclipses related?

Answer 1

Tides, moon phases and eclipses are all related to the Moon's orbit.

Explanation:

As the Moon orbits the Earth and the Earth spins on its axis, the Moon's gravity pulls the oceans into a towards it. Conservation laws also cause another ocean bulge on the opposite side of the Earth to the Moon. This causes the 12 hour tide cycle as every location will experience a high tide when it is below the Moon and on the opposite side to the Moon.

At a full or new moon when the Sun, Moon and Earth are aligned, tides are larger as the Moon and Sun's gravity combine to create a larger bulge. These are known as Spring Tides. It is nothing to do with the season Spring, it is that the tide springs forward.

We see the Moon by reflected sunlight from the Moon's surface. When the Moon is between the Sun and Earth it is a new moon. There is no reflected sunlight from the near side and we can't see it.

As the Moon continues on its orbit, more and more of the near side surface reflects sunlight. We see this as the moon phases: new moon, waxing crescent, half moon waxing gibbous.

When the Moon is on the opposite side of the Sun to the Earth, all of its near side reflects sunlight and we have a full moon. It then proceeds through its waning phases until it is again a new moon.

An eclipse occurs when the Sun, Earth and Moon are aligned. A lunar eclipse occurs when the Earth casts a shadow on the Moon and can only happen at full moon. A solar eclipse occurs when the Moon casts a shadow on the Earth which can only happen at new moon.

As the Moon's orbit is inclined at an angle of `5^@` to the ecliptic, which is the plane of the Earth's orbit, an eclipse can only occur when the Moon is near one of its nodes which are the points where the Moon's orbit crosses the Earth's orbit.