The Coast News Group
The Sea of Tranquility, where Apollo 11 landed. Photo by Kyle Stock
Coastal Cosmos Columns

Studying the mysterious impact the moon has on Earth

What do you see when you look up at the full moon? A face? A rabbit? A spotted gray, a glowing circle? Or do you see a majestic world, created from the Earth, having an astronomical impact on its development and mass cultural significance?The moon is the Earth’s only natural satellite, orbiting every 29.5 days at a speed of 2,286 miles per hour. The moon is, on average, 240,000 miles from the Earth. Thirty Earths could be lined between the two. The moon has a circumference of 6,786 miles. Fifty moons would fit into the volume of Earth.The moon’s effect on the Earth is almost incalculable. Relative to the size of the planet, the moon is the largest satellite in the solar system. The moon is responsible for about 66 percent of the tidal forces on the Earth’s oceans.

The rest is caused by the sun. Tides are caused by gravity pulling an oblong bulge in the Ocean toward the moon/sun.

The Lunar Eclipse, Dec. 10, 2011, when the Earth passed between the sun and Moon. Photo by Kyle Stock

In San Diego, we experience two high tides and two low tides each day. This is called semi-diurnal. When our coastline is facing the moon and we are inside the bulge, it is high tide. When we are outside the bulge, it is low tide. During a new and full moon, the moon, Earth and sun are in alignment, causing more extreme tide changes, known as a spring tide. The first and third quarter moons are out of alliance and the tide changes are at a minimum, called a neap tide.

Ecology suggests that the changing tides have had a vital role in the evolution of life, as the inter-tidal zone goes from submerged to dry multiple times a day. Early life adapted to the constant change and eventually ventured onto the land. The ever-changing orb in the sky has enthralled, terrified and inspired humans since the beginning.
Mythologies the world over have lunar deities: Luna in Roman, Selene in Greek, Khonsu in Egyptian, Chandra in Hinduism, Lona in Hawaiian/Polynesian and many others.

The moon is the site of the greatest human achievement. Between July 1969 and December 1972, 12 men from NASA’s Apollo program explored the lunar surface. The science that came from these efforts, from the collected rocks to the science equipment left behind, has exponentially increased our understanding of the moon, Earth and solar system.

The prevailing theory for the moon’s formation is called the Giant Impact Hypothesis. As the solar system coalesced around the newly formed sun 4.5 billion years ago, it was a very crowded space.

Dozens of planets contended to find a clear spot in the lineup. The young, molten earth was following its path around the sun, then one day, bang! A Mars-sized object named Theia (Greek mother of Selene), smashed into the Earth. Theia was instantly blown to bits and a large chunk of the Earth was ejected into space. All of this material became a ring around the Earth, like Saturn’s. Within 100 years, gravity caused much of this material to combine into Luna.

At first, the moon was very close to Earth causing enormous 1,000-feet tide swings as the moon pulled the ocean miles inland and back and forth.

The moon is moving away from the Earth at a rate of about 1.5 inches per year. It is a beautiful coincidence of our time that a total solar eclipse is even possible.

Ten thousand years from now, as the moon moves away, it will not cover the entire face of the sun in our sky.
Looking for an invigorating experience? During the next Waxing Gibbous Moon, go surfing! Obviously, the moon does not create its own light, but it does reflect enough light from the sun to provide an exciting opportunity in the ocean.

The sensory deprivation makes a waist high wave feel head high.