Everything Everywhere Daily: History, Science, Geography & More - The Moon

Starting point is 00:00:00 Approximately 384,000 kilometers, or 239,000 miles above the surface of the Earth is our planet's only natural satellite, the moon. Every culture and civilization on the planet has had the moon play a role in its legends, and they've also used the moon to keep track of time, plant, and harvest. Scientists have wondered where the moon comes from and how it was formed, and with data gathered over the last several decades, we now have a better understanding of its origin. Learn more about the moon, its origin, composition, and its role in helping develop life on Earth on this episode of Everything Everywhere Daily. What if your perceptions about the past were wrong? ThruLine is a podcast that takes you back in time to uncover the parts of the story that may have gone unnoticed. It effectively turned day into night. And how it shaped the world now.

Starting point is 00:01:07 Time travel with us. every week on the Thulein podcast from NPR. I've done many episodes that reference the moon, including episodes on moon rocks and the Apollo missions, but in this episode, I want to focus on the moon itself. The moon is one of the few universal things that every culture and civilization in history has in common. No matter where you are in the world, regardless of the continent or even the latitude, everyone is familiar with the moon.

Starting point is 00:01:40 As such, almost every culture has a myth. about the moon. In China, Chung-e is the moon goddess living on the moon with her pet rabbit, the jade rabbit. According to the legend, she drank an elixir of immortality and floated up to the moon where she resides eternally. In Hindu mythology, Chandra, also known as Soma is the moon god. He's depicted as a beautiful, youthful deity who rides a chariot across the night sky. In some West African legends, Anansi the spider, a trickster figure, is associated with the moon. One story tells how a Nazi tried to steal the moon and keep it for himself, but he was caught and the moon was placed high in the sky out of his reach to provide light for

Starting point is 00:02:18 everyone. In various Native American cultures, the moon and the sun are often seen as siblings or spouses. For example, in the Inuit tradition, the moon god Ghaluk chases his sister, the sun goddess Molina, across the sky. This chase explains the cyclical nature of night and day. Another story from the Cree involves the moon as a protective figure watching over the earth. Over time, we moved from making stories about the moon to asking serious questions about the moon and making serious measurements and observations. Certain things have been known about the moon

Starting point is 00:02:51 since time immemorial. We know that we only see one side of the moon, that it goes through phases over the course of a month and that it's associated with the tides. In 1609, Galileo Galilei turned a telescope towards the moon for the very first time and made some startling discusses. He saw that the moon's surface was not smooth as people had always assumed. Rather, it was full of mountains and craters. Galileo, like centuries of astronomers after him, assumed that the craters on the moon were formed by volcanoes. In the 1870s, the English astronomer Richard Proctor theorized that the craters on the moon were not volcanic, but were the result of impacts. Knowledge of the moon increased throughout the early 20th century as telescopes improved. We

Starting point is 00:03:38 were able to map the surface better and could identify the major features. Roughly speaking, two types of features on the moon surface can be identified with the naked eye or telescope. The dark parts of the moon are lunar maria, and this comes from the Latin word for sea. The sea of tranquility, for example, the landing site of Apollo 7, is formerly known as the mer tranquilitatus. The light parts of the moon surface are known as highlands. As much information as could be gleaned from direct observation, there were some things about the moon that couldn't be known unless samples could be studied. The only way to truly know the moon's chemical composition would be to collect samples and bring them back to Earth. The Apollo program retrieved the

Starting point is 00:04:23 first moon rock samples, which have been studied extensively for over 50 years, and subsequent Soviet and Chinese unmanned missions have also returned samples to Earth. So with some actual samples available for geologists to study, what have we learned? The first big question that geologists had was, how old is the moon? Using uranium-led dating of zircon minerals found in some of the rocks, researchers concluded that the rocks were between 4.1 and 4.4 billion years old. Approximately the same age as the oldest rocks found on Earth. The rocks are primarily composed of silicate materials such as basalt and anorthosite,

Starting point is 00:05:03 similar to the Earth's crust, but with distinct differences. Notably, the moon lacks volatile. elements like water, which are abundant on Earth. Any water found on the surface of the moon would have been lost billions of years ago through a process known as photo disassociation. The harsh, unfiltered light of the sun and cosmic rays beating down on the surface would have long since split apart water molecules. The oxygen and hydrogen would have then been lost to space. While water isn't commonly found on the surface of the moon, that does not mean that the moon is devoid of water. Over the last several decades, probes sent to orbit the moon by NASA and the Indian Space Agency

Starting point is 00:05:43 have found evidence of frozen water near the polar regions, which is a bit more abundant near the South Pole. Why the poles? Those areas don't get a lot of direct sunlight, and water inside a crater located near the poles would never see any direct sunlight. This water may have been there since the formation of the moon, or it may have been deposited there by a comet that crashed into the surface. This is important because a source of water would be critical if humans ever want to establish a permanent base on the moon. Another discovery is that the moon is mostly geologically inactive today, and it probably hasn't been for at least the last few billion years. However, about four billion years ago, the moon

Starting point is 00:06:25 went through a period known as the late heavy bombardment. This was a period of extensive bombardment of the lunar surface with projectiles from the early solar system, and this would have made the surface of the moon very hot and possibly even molten. There was also a period of intense volcanism which took place about four to three billion years ago. Evidence of this volcanism can be seen in lava tubes which are believed to exist on the moon. As with water, lava tubes might be able to help humans establish a base on the moon by providing a ready-made shelter with protection from the sun and cosmic rays. One of the other discoveries was that some of the moon rocks were weakly magnetic, and this implies that at some point, very soon after the creation of the moon,

Starting point is 00:07:11 there may have been a short period where the moon had a molten core and a weak magnetic field. This is quite a bit of information that's been deciphered from moon rocks, and this really leaves the big question of where the moon comes from and how it was created. Our moon is very different from the moons of other planets in our solar system in one big way. Our moon is relatively huge compared to the planet at orbits, compared to every other moon. The only pair of objects with a greater ratio is Pluto and its moon charon. Our moon is the fifth largest natural satellite in the solar system, but the four others that are larger all orbit Jupiter or Saturn, and are tiny in comparison to their planets. Moreover, Jupiter and Saturn are gas giants, and the Earth is a rocky planet that is more similar in chemical composition,

Starting point is 00:08:03 to the moon. There are several theories as to how the moon might have come into being. One theory is called the capture theory. The capture theory suggests that the moon forms somewhere else in the solar system and then was captured by the Earth's gravity. This theory is less favored because it requires highly specific conditions for a body to be captured by another planet without being destroyed or escaping. Also, the similar chemical composition and age of the Earth and the Moon make this highly improbable. Another theory is the co-formation theory. The co-formation theory proposes that the moon forms simultaneously with the Earth from the primordial accretion disk of the solar system.

Starting point is 00:08:45 However, this theory has its limitations, as it doesn't adequately explain the differences in the composition between the Earth and the Moon. The most widely accepted theory at this point, however, is the giant impact hypothesis. This theory suggests that about 4.5 billion years ago, a Mars-sized body often referred to as Thia collided with the early Earth. This impact was so powerful that it ejected a significant amount of debris into Earth's orbit. This debris eventually coalesced to form the Moon. This hypothesis is supported by several lines of evidence, including the Moon's composition, which is similar to the Earth's mantle, and the angular momentum of the Earth-moon system. Another question that many people have is, why can we only see one half of the moon?

Starting point is 00:09:34 The other side of the moon that we cannot see has been called the dark side of the moon, but it isn't technically dark. It gets just as much light as the other side of the moon does. We can only see one side of the moon because it has become tidally locked. Tidal locking occurs when the time it takes for an object to revolve about its own axis happens to be the same as the time it takes to orbit an object. Everything I've talked about so far in this episode has been about the moon itself. However, many researchers now believe that the moon might have been critical for the development

Starting point is 00:10:09 of life on Earth. For starters, the moon and its relative size serve as a giant shield protecting the planet from asteroid impacts. Every crater on the surface of the moon represents a meteor that could have hit Earth. The presence of the moon also stabilizes the axial tilt of the Earth. Without the Moon, the Earth's tilt could otherwise be very dramatic, leading to extreme changes in climate over very short geological time scales. A stable axial tilt ensures relatively stable seasons, which is beneficial for developing and evolving complex life forms. The Moon's gravity also causes tides in the Earth's ocean. Tides play a crucial role in mixing of ocean waters, which helps distribute nutrients and gases like oxygen and carbon dioxide. This

Starting point is 00:10:58 mixing creates diverse marine environments and may have been essential for the development of early life in tidal pools and coastal areas. The moon's influence on tides also affects the circulation of ocean currents, which helps distribute heat around the planet. This process can mitigate extreme temperatures and create a more hospitable climate for life. Many astronomers now believe that the moon has had such an important part to play in the evolution of life that if we search for exoplanets that might have life, we should start searching for smaller planets with large moons. Our knowledge of the moon is far from over. In fact, we really haven't even gotten started. All of the Apollo and unmanned sample return missions combined have only returned 381 kilograms

Starting point is 00:11:46 or 840 pounds of moon rock, and those samples have only been collected from a small number of sites. There are plans to send humans back to the moon this decade and potentially set up a permanent base on the moon. This would result in an exponential increase in the amount of data we would have on the moon and would increase our understanding of the moon accordingly. The moon has been a global constant for humanity throughout all of history, yet until recently we really didn't know much about it. Now we finally have a glimpse into the moon's secrets and over the course of the rest of the 21st century, we're poised to learn even more.

Starting point is 00:12:29 The executive producer of Everything Everywhere Daily is Charles Daniel. The associate producers are Benji Long and Cameron Kiever. I want to give a big shout out to everyone who supports the show over on Patreon, including the show's producers. Your support helps me put out a show every single day. And also, Patreon is currently the only place where Everything Everywhere Daily merchandise is available to the top tier of supporters. If you'd like to talk to other listeners of the show and members of the Completionist Club,

Starting point is 00:12:55 you can join the Everything Everywhere Daily Facebook group or Discord server. Links to everything are in the show notes. Hello, Carl, I am Ignignock, and this is Er. I am Err. We are Moonenites from the inner core of the Moon. You said it right. Our race is hundreds of years beyond yours. Man, do you hear he's saying?

Starting point is 00:13:19 Some would say that the Earth is our Moon. We're the Moon. But that would be little the name of our Moon, which is the Moon. The point is we're at the center, not you.

Everything Everywhere Daily: History, Science, Geography & More - The Moon

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