Our Moon 4.5 Billion Years Ago The Solar System is still very young, and the Earth is a molten blob orbiting the Sun. An object the size of Mars hits the Earth. Large sections of the planet break away and, pulled by Earth’s gravity, begin to orbit Earth. Their own forces of gravity pull the pieces together to form the Moon.

Our Moon 4.4 Billion Years Ago Parts of the Moon’s surface have cooled enough for molten materials to solidify as rocks. Other debris in the Solar System strike the Moon. The impact cuts wide craters in the Moon’s surface. In some areas, cracks and deep fissures form.

3.9 Billion Years Ago Hot molten rock from the Moon’s interior oozes out on to the surface. Many craters are filled, and the molten hardens creating dark, flat marks on the Moon’s face. The marks are called seas.

Our Moon 3.2 Billion Years Ago The lava stops flowing. Today, the Moon has no air, internal heat or life. It does not produce light; rather, the Moon reflects sunlight. The phases of the Moon occur because the Moon orbits the Earth and the Earth orbits around the Sun.

AAAAlthough small, the Moon impacts the Earth in many ways. For example, the gravitational pull of the Moon produces tides in the Earth’s oceans. How? AAAAs the Earth turns on its axis, different parts of the Earth face the moon. The oceans facing the moon are “pulled” toward the moon…especially at the part of the Earth closest to the moon (i.e., the equator). This creates a “bulge” in the ocean This is only one part of the story…

RRRRecall, the sun’s gravitational pull on the Earth. The Earth spinning and orbiting creates a centrifugal force which would cause the Earth to fly off into space, but the gravitational force exerted by the sun pulls the Earth towards the sun and keeps the Earth in a constant orbit around the sun. TTTThe sun is on the opposite side of the Earth from the moon. Thus, a water bulge occurs in the Earth’s oceans on the side facing the sun…with the largest bulge at the equator.

TTTThe result is two bulges of water caused by the sun: (1) a centrifugal bulge and (2) a gravitational bulge. SSSSo, does the moon’s pull offset the sun’s pull? No. The pulls are not equal. NNNNote: The moon does not orbit the Earth. The Earth and moon orbit each other. TTTThe moon is also smaller than the sun. So, the sun’s impact is greater? No.

TTTThe moon is closer to the Earth than the sun. Size is not important; rather, distance is vital. TTTThe moon exerts the largest influence on tidal motion with the sun exerting the second largest influence. Hence, the ocean tides follow the cycling of the moon modified somewhat by the sun.

TTTTo complicate matters…the Earth is constantly rotating. Thus, the portion of the Earth facing the moon rotates away from the moon’s gravitational pull. The water bulge moves to face the moon’s pull. Thus, a tide is formed. SSSSince the orbiting of the Earth and the moon is slightly more than 24 hours, the timing of the tide appears to move.