The reflection of the sun's rays on Earth's surface is what viewers see as the phases. A full moon occurs approximately every 28 days. The moon has several phases. The phases cause the tides. Many think that the phases affect people’s moods.
The moon has eight phases. It starts as a new moon with no light reflecting from the sun. Next, a crescent appears as a thin light. A week later, a half moon appears - the first quarter. The half moon glows fuller with each passing day until the full moon appears. A week after the full moon, less of the moon shows. The phases reverse revealing the third quarter, the crescent and then the new moon.
The moon and Earth rotate on separate axises. The moon rotates about fifty minutes slower. Thus, observers see varying parts of the moon lit, the phases. The moon is Earth’s satellite. They travel the same path around the sun. To fully understand the rotation between the Earth and moon, an experiment helps. Choose two people to represent the moon and the Earth. The moon rotates on its own axis. Similarly, the Earth rotates. But the moon rotates around the Earth, the systems continue, and light reveals different portions of the objects. A flashlight trained on both shows how the phases develop. The light that observers see is light from the sun.
Eclipses reveal that at special times the sun, Earth and moon line up. When the moon is between the sun and Earth, a solar or annular eclipse occurs. If the Earth is between the sun and the moon, a lunar eclipse results. As the light hits the moon, it reveals the different phases.
The exact time that it takes the moon to revolve around the Earth is 28.5 days. The moon rotates slowly. Early calendars used the moon as its guide. Today, most nations use the sun.
Tides reveal that the moon’s movement effects gravity. At different times throughout the month, the tides are either higher, spring tides, or lower, neap tides, than at other times. When the tides are lower, red tides occur which can cause health issues for fishermen and beach-goers.
On the moon, observers see the full Earth, crescent Earth, first and third quarter, Earth. The phases occur because of rotation. Light reflecting from the sun illuminates different parts of the moon.