Your Daily Facts about our Moon
How did the moon form? According to the “giant impact” theory, the young Earth had no moon. At some point in Earth’s early history, a rogue planet, larger than Mars, struck the Earth in a great, glancing blow. Instantly, most of the rogue body and a sizable chunk of Earth were vaporized. The cloud rose to above 13,700 miles (22,000 kilometers) altitude, where it condensed into innumerable solid particles that orbited the Earth as they aggregated into ever larger moonlets, which eventually combined to form the moon.
The distance between the Earth and its moon averages about 238,900 miles (384,000 kilometers). The diameter of the moon is 2,160 miles (3,476 kilometers). The moon’s mass—the amount of material that makes up the moon—is about one-eightieth of the Earth’s mass.
As you read this, the Moon is moving away from us. Each year, the Moon steals some of Earth’s rotational energy, and uses it to propel itself about 3.8 centimeters higher in its orbit. Researchers say that when it formed, the Moon was about 14,000 miles (22,530 kilometers) from Earth. It’s now more than 280,000 miles, or 450,000 kilometers away.
Because the force of gravity at the surface of an object is the result of the object’s mass and size, the surface gravity of the moon is only one-sixth that of the Earth. The force gravity exerts on a person determines the person’s weight. Even though your mass would be the same on Earth and the moon, if you weigh 132 pounds (60 kilograms) on Earth, you would weigh about 22 pounds (10 kilograms) on the moon.
The rotation of the moon—the time it takes to spin once around on its own axis—takes the same amount of time as the moon takes to complete one orbit of the Earth, about 27.3 days. This means the moon’s rotation is synchronized in a way that causes the moon to show the same face to the Earth at all times. One hemisphere always faces us, while the other always faces away. The lunar far side (aka the dark side) has been photographed only from spacecraft.
The shape of the moon appears to change in a repeating cycle when viewed from the Earth because the amount of illuminated moon we see varies, depending on the moon’s position in relation to the Earth and the sun. We see the full moon when the sun is directly behind us, illuminating a full hemisphere of the moon when it is directly in front of us. The new moon, when the moon is darkened, occurs when the moon is almost directly between Earth and the sun—the sun’s light illuminates only the far side of the moon (the side we can’t see from Earth).
The moon orbits the Earth at an average speed of 2,300 miles an hour (3,700 kilometers an hour).
The moon’s gravitational pull on the Earth is the main cause of the rise and fall of ocean tides. The moon’s gravitational pull causes two bulges of water on the Earth’s oceans—one where ocean waters face the moon and the pull is strongest and one where ocean waters face away from the moon and the pull is weakest. Both bulges cause high tides. These are high tides. As the Earth rotates, the bulges move around it, one always facing the moon, the other directly opposite. The combined forces of gravity, the Earth’s rotation, and other factors usually cause two high tides and two low tides each day.
The airless lunar surface bakes in the sun at up to 243 degrees Fahrenheit (117 degrees Celsius) for two weeks at a time (the lunar day lasts about a month). Then, for an equal period, the same spot is in the dark. The dark side cools to about -272 degrees Fahrenheit (-169 degrees Celsius).
We all know there was a man on the moon, but did you know that there is one who stayed there? Dr. Eugene Shoemaker, a Geological Surveyor, who educated the Apollo mission astronauts about craters, never made it into space himself, but it had always been one of his dreams. He was rejected as an astronaut because of medical problems. After he died, his ashes were placed on board the Lunar Prospector spacecraft on January 6, 1999, which was crashed into a crater on the moon on July 31, 1999. The mission was to discover if there was water on the moon at the time, but it also served to fulfill Dr Shoemaker’s last wish.
When Neil Armstrong took that historical step of “one small step for man one giant step for mankind” it would not have occurred to anyone that the step he took in the dust of the moon was there to stay. It will be there for at least 10 million years.
When Alan Sheppard was on the moon, he hit a golf ball and drove it 2,400 feet, nearly one half a mile.
In a survey conducted in 1988, 13% of those surveyed believed that the moon is made of cheese.