Science, Tech, Math › Science All About the Moon Interesting Moon Facts Share Flipboard Email Print Science Astronomy Solar System An Introduction to Astronomy Important Astronomers Stars, Planets, and Galaxies Space Exploration Chemistry Biology Physics Geology Weather & Climate By John P. Millis, Ph.D Professor of Physics and Astronomy Ph.D., Physics and Astronomy, Purdue University B.S., Physics, Purdue University John P. Millis, Ph.D. is a professor of physics and astronomy at Anderson University. He conducts research at the VERITAS gamma-ray observatory in southern Arizona. our editorial process John P. Millis, Ph.D Updated May 06, 2019 The Moon is Earth's large natural satellite. It orbits our planet and has done so since early in solar system history. The Moon is a rocky body that humans have visited and are continuing to explore with remotely operated spacecraft. It's also the subject of much myth and lore. Let's learn more about our nearest neighbor in space. Edited and updated by Carolyn Collins Petersen. 01 of 11 The Moon Likely Formed as a Result of a Collision Early in Solar System History. There have been many theories of how the Moon formed. After the Apollo moon landings and the study of the rocks they returned, the most likely explanation of the Moon's birth is that infant Earth collided with a Mars-sized planetesimal. That sprayed material out to space that eventually coalesced to form what we now call our Moon. 02 of 11 Gravity on the Moon is Much Less than on Earth. A person who weighs 180 pounds on Earth would weigh only 30 pounds on the Moon. It is for this reason that the astronauts could maneuver so easily on the lunar surface, despite all the massive equipment (especially their space suites!) that they toted along. By comparison everything was much lighter. 03 of 11 The Moon Affects Tides on Earth. The gravitational force created by the Moon is significantly less than that of Earth, but that doesn’t mean that it doesn’t have an affect. As the Earth rotates, the water bulge around the Earth is pulled along by the orbiting Moon, creating a high and low tide each day. 04 of 11 We Always See the Same Side of the Moon. The Most people are under the mistaken impression that the Moon doesn’t rotate at all. It actually does rotate, but at the same rate it orbits our planet. That causes us to always see the same side of the Moon facing Earth. If it didn’t at least rotate once, we would see every side of the Moon. 05 of 11 There is No Permanent “Dark Side” of the Moon. This is really a confusion of terms. Many people describe the side of the Moon that we never see as the dark side. It is more appropriate to refer to that side of the Moon as the Far Side, since it is always farther away from us than the side facing us. But the far side isn’t always dark. In fact it is lit up brilliantly when the Moon is between us and the Sun. 06 of 11 The Moon Experiences Extreme Temperature Shifts Every Couple Weeks. Because it has no atmosphere and rotates so slowly, any particular surface patch on the Moon will experience wild temperature extremes, from a low of -272 degrees F (-168 C) to highs approaching 243 degrees F (117.2 C). As the lunar terrain experiences changes in light and darkness about every two weeks, there is no circulation of the heat as there is on Earth (thanks to wind and other atmospheric effects). So, the Moon is at the complete mercy of whether the Sun is overhead or not. 07 of 11 The Coldest Place Known in our Solar System is on the Moon. When discussing the coldest places in the solar system, one immediately thinks of the farthest reaches of our Sun’s rays, like where Pluto inhabits. According to measurements taken by NASA space probes, the coldest place in our little neck of the woods is on our very own Moon. It lies deep inside lunar craters, in places that never experience sunlight. The temperatures in these craters, which lie near the poles, approach 35 kelvin (about -238 C or -396 F). 08 of 11 The Moon has Water. In the last two decades NASA has crashed a series of probes into the lunar surface to measure the amount of water in or beneath the rocks. What they found was surprising, there was much more H2O present than anyone had previously thought. In addition, there's evidence of water ice at the poles, hidden in craters that get no sunlight. In spite of these findings, the Moon’s surface is still dryer than the driest desert on Earth. 09 of 11 The Moon’s Surface Features Formed through Volcanism and Impacts. The Moon's surface has been changed by volcanic flows early in its history. As it cooled, it was bombarded (and continues to be hit) by asteroids and meteoroids. It also turns out that the Moon (along with our own atmosphere) has played an important role in protecting us from the same kinds of impacts that have scarred its surface. 10 of 11 Dark Spots on the Moon were Created as Lava Filled in Craters Left by Asteroids. Early in its formation, lava flowed on the Moon. Asteroids and comets would come crashing down and the craters they dug out penetrated down to molten rock beneath the crust. The lava oozed up to the surface and fill in the craters, leaving behind an even, smooth surface. We now see that cooled lava as relatively smooth spots on the moon, pockmarked with smaller craters from later impacts. 11 of 11 BONUS: The Term Blue Moon Refers to a Month that Sees Two Full Moons. Poll a classroom of undergraduates and you’ll get a variety of suggestions to what the term Blue Moon refers. The simply fact of the matter is that it is simply a reference to when the Moon appears full twice in the same month.