OUR BEAUTIFUL
MAGICKAL MOON!
MAGICKAL MOON!
Month after month, the Moon reigns as the most obvious and beautiful thing in the night sky. But how much do you know about the Moon? Can you name even the biggest craters? Have you ever seen a Moon tree? And do you know what gives the Moon its subtle colors?
Avid Moonwatchers say the best time to view it is not just during a full Moon, but also around the time of first quarter or last quarter. For about a week around each of these times, the Sun strikes the Moon's surface at a steep angle, rendering craters in sharp relief. Though it's tempting to use a telescope, your first explorations should be with the naked eye. Become familiar with the Moon's major features. Then use binoculars to study the features more closely. Learn the names of a few craters and plains (called maria, after the Latin word "mare," which means sea). If you use a telescope, zero in on the line where light and shadow meet. Here you'll see the greatest contrast and the most detail.
The Moon has a story to tell. And much of its story is like an open book, born of a violent past, worn on the lunar surface as ancient round pockmarks and streaks of fresh, bright material. It's a story that scientists started piecing together in 1609 when Galileo Galilei first turned a telescope on the Moon. Galileo Galilei did not invent the telescope, but he was the first to realize its importance for astronomy, and he used his great engineering skills to craft improved lenses for the crude devices, which were at first called spyglasses or eyeglasses (a colleague of Galileo's later dubbed them telescopes). When Galileo turned his own handmade device on the Moon in 1609, he turned conventional thinking on its head. Amazed at what he saw, Galileo wrote that the Moon "is like the face of Earth itself," marked with mountains and valleys. The discovery surprised the heck out of his contemporaries, too, most of whom still believed Aristotle's idea that the heavens were made of unearthly matter -- ether or quintessence -- that was immutable and incorruptible, meaning it couldn't have jagged edges. With a small telescope, or even a pair of binoculars, you can share Galileo's thrill as the Moon's mountains and valleys jump out in stark relief.
The book evolved slowly. In the 1800s, people claimed to see settlements on the Moon. And it wasn't until the middle 20th Century that scientists agreed on what caused the Moon's craters. Then beginning in the 1960s, Apollo astronauts added many chapters to the book by bringing back rocks and photographs from the surface. Even if you don't have a telescope or a pair of binoculars, you can go out and look at the Moon and make a discovery. There are two kinds of rock that you can see from Earth, even with the naked eye. When you look up at the Moon you see a bright disk and dark splotches. The bright areas are the ancient crust leftover from the Moon's formation, and the dark areas are relatively newer rock that formed from lava that erupted from the interior. Those are the so-called seas. They are made out of lava rock like we find in Hawaii. Except that in Hawaii, if you pick up a rock, it's likely to be maybe 100 years, or maybe it's a year old, or maybe it formed last week. But on the Moon, it's likely to be 3.5 billion years old. With binoculars, you'll start to see some of the surface features. In particular, you can see some of the Moon's largest craters. The craters tell you that the Moon was the victim of some cosmic target practice. You can see that the Moon was a pretty violent place when the planets were forming. Each one of those craters is the result of an impact that was so violent it dwarfs any atomic weapons we have on Earth.
The next question one might ask is why doesn't the Earth show the same kind of scars. Well, it does have a few, like Meteor Crater in Arizona. But most of the impact craters on the Earth were erased by the forces of wind and rain and the shifting continents, including mountain-building events and volcanism. But the Moon is pretty much untouched for the last 3 billion years, so it's kind of like a museum for that violent era. If you have a good telescope, you can start to look the details of craters. Some of the big craters have walls that look terraced like a staircase, and this is because right after the crater was blasted out of the Moon's crust, the rock that formed the walls of the crater was fractured by the impact and slumped down, or collapsed, to form a series of stair steps. Many of these large craters have flat floors covered with fairly dark rock that look somewhat like seas or ponds. This is actually impact melt, which is material that had been melted by the giant impact and then rained back down into the crater and cooled. If you look in the middle of many of these large craters, you'll see some very large mountains sticking up. It's hard to tell how big these things are when you're looking through a telescope, but you can rest assured that these mountains are thousands of feet high. These are called central peaks, and they formed when the crust rebounded after the impact. There are craters all over the Moon in various stages of preservation. Many are much more beaten up, and have craters on top of craters. But the youngest craters have what look like rays of bright material coming from them. These rays are made of ejecta that were blasted out of the crust when the crater formed and sprayed across the landscape. The best example is the crater Tycho, which is in the southern highlands. It's one of the best-preserved large impact craters on the Moon. You can see its ray pattern across much of the Moon's near side with binoculars, or sometimes even with the naked eye if you've got good eyes. Finally, the dark lava seas are themselves filling in giant impact craters that are called impact basins. These basins can be hundreds of miles (kilometers) across. Mare Imbrium is one such giant impact basin. You can still see its round shape. The basins are places where absolutely gigantic impacts took place. If they had been much bigger, they could have broken the Moon apart. Through a telescope or binoculars, you'll also see that the Moon has a grayish-tan color. It's a very subtle shade. And it is exactly the color that the astronauts described when they went there. So you can actually get a little sense of what they saw by looking at the Moon yourself.
To the unaided eye, the Moon's surface appears mottled with irregular patches of gray amid splashes of white. These darker patches are known as maria, Latin for seas, since that is how they appeared to early skywatchers. We know them now as areas where lava pooled on the lunar surface billions of years ago, probably after an asteroid punched through the thin lunar crust. Together, the light and dark regions arrange themselves into the popular face of the "Man in the Moon." They were interpreted as a "rabbit in the Moon" by the Maya and Aztecs of ancient Mexico, as well as the Mimbres Indians of the southwestern United States. The Moon preserves a record of the pummeling it took 4.1 to 3.8 billion years ago. Earth got nailed by even more space rocks back then, but the planet swallowed the evidence by recycling it into the interior over the eons. As sublime as the Moon appears to the eye, a pair of binoculars turns this marbled world into a breathtaking wonder. One of the best times to look at the Moon with any optical aid is during its crescent and quarter phases. At that time, the low, slanting angle of the rising Sun creates deep dark shadows in valleys and crater floors that contrast sharply with bright mountain ranges and crater rims. When the Moon is full, it is essentially "noontime" there, with the Sun overhead. Though this geometry makes the Moon appear very bright as seen from Earth, it lowers the contrast of the lunar features. With a small telescope, a number of prominent lunar features may be observed at first or last quarter. Some of these may also be seen when the Moon is full, but as mentioned, their contrast will be significantly reduced. Moreover, the Moon is so bright that even at first or last quarter it can dazzle the eye (never mind its glaring appearance at full phase!).
Let's begin by considering the Moon's prominent features at first quarter: Near the upper eastern (right) limb (as the Moon appears to the naked eye and in binoculars), is the round, dark basin known as Mare Crisium. This region can be seen standing in the full glare of the Sun during the early crescent stages. Our perspective of Crisium on the curve of the Moon's limb often gives it an oval appearance. To the west (left) lies Mare Tranquillitatis, the region of the first manned lunar landing. (By the way, none of the Apollo landing bases can be detected in telescopes from Earth.) Above and slightly to its left is another round basin, Mare Serenitatis, which stands partly in shadow. Serenitatis is rimmed on its western (or left) edge by great mountain chains. Along the terminator, which is the dividing line between the lit and unlit regions of the Moon, many craters stand out in sharp light and shadow. Most prominent is the trio Theophilus, Cyrillus, and Catharina, all lying just below center. Theophilus and Cyrillus are actually overlapping and look like a figure 8. Catharina lies a little below them. Another prominent crater, Aristoteles, lies along the upper terminator, near the Moon's North Pole. Near first quarter it has a bright west rim, with the floor in deep shadow. Lined up neatly along the terminator at first quarter, just below the lunar equator, are three prominent walled plains. Ptolemaeus lies furthest north (uppermost) and has a number of craters and pits within it. Adjoined to Ptolemaeus to the south, and slightly smaller, is Alphonsus, site of the robotic Ranger 9 landing in March 1965. Finally, just below Alphonsus, is Arzachel, a very conspicuous crater with terraced clefts along its rim and a prominent central peak.
At last quarter, the western (or left) half of the Moon is lit. One of the more prominent features is Oceanus Procellarum in the upper left quadrant, a sprawling expanse of dark basalt punctuated by the white chalk-like streak of Aristarchus, a very recent impact crater. Observers with telescopes have reported unusual brightness and color changes in this feature, which are considered to be attributable to gas emissions from within the crust. Further east (right) is Mare Imbrium, a large, round basin that makes up one of the "eyes" of the Man in the Moon. Two bright ray craters, Copernicus and Kepler, lie near the equator in this section. The rays are produced by material ejected when an asteroid or comet struck the surface, splashing out bright fresh material from below. Mare Nubium lies directly below, or south, of Imbrium in the Moon's southern hemisphere. Mare Humorum, one of the smallest of the maria, lies to the west, or left. Most of the Moon's southern hemisphere is rugged and pockmarked with craters, including the bright ray crater Tycho. To its south lies Clavius, one of the most dominant walled plains in this sector of the Moon. Its rim and floor are pitted with a variety of craters. You don't have to wait until the Moon is full to appreciate our closest celestial neighbor. As lifeless as it appears in binoculars or a telescope, the shadow show at quarter phase imparts a dynamic quality to the lunar craggy surface. All at once, the Moon ceases to be a beautiful bauble floating over Earth's landscape and becomes a world unto its own.
Avid Moonwatchers say the best time to view it is not just during a full Moon, but also around the time of first quarter or last quarter. For about a week around each of these times, the Sun strikes the Moon's surface at a steep angle, rendering craters in sharp relief. Though it's tempting to use a telescope, your first explorations should be with the naked eye. Become familiar with the Moon's major features. Then use binoculars to study the features more closely. Learn the names of a few craters and plains (called maria, after the Latin word "mare," which means sea). If you use a telescope, zero in on the line where light and shadow meet. Here you'll see the greatest contrast and the most detail.
The Moon has a story to tell. And much of its story is like an open book, born of a violent past, worn on the lunar surface as ancient round pockmarks and streaks of fresh, bright material. It's a story that scientists started piecing together in 1609 when Galileo Galilei first turned a telescope on the Moon. Galileo Galilei did not invent the telescope, but he was the first to realize its importance for astronomy, and he used his great engineering skills to craft improved lenses for the crude devices, which were at first called spyglasses or eyeglasses (a colleague of Galileo's later dubbed them telescopes). When Galileo turned his own handmade device on the Moon in 1609, he turned conventional thinking on its head. Amazed at what he saw, Galileo wrote that the Moon "is like the face of Earth itself," marked with mountains and valleys. The discovery surprised the heck out of his contemporaries, too, most of whom still believed Aristotle's idea that the heavens were made of unearthly matter -- ether or quintessence -- that was immutable and incorruptible, meaning it couldn't have jagged edges. With a small telescope, or even a pair of binoculars, you can share Galileo's thrill as the Moon's mountains and valleys jump out in stark relief.
The book evolved slowly. In the 1800s, people claimed to see settlements on the Moon. And it wasn't until the middle 20th Century that scientists agreed on what caused the Moon's craters. Then beginning in the 1960s, Apollo astronauts added many chapters to the book by bringing back rocks and photographs from the surface. Even if you don't have a telescope or a pair of binoculars, you can go out and look at the Moon and make a discovery. There are two kinds of rock that you can see from Earth, even with the naked eye. When you look up at the Moon you see a bright disk and dark splotches. The bright areas are the ancient crust leftover from the Moon's formation, and the dark areas are relatively newer rock that formed from lava that erupted from the interior. Those are the so-called seas. They are made out of lava rock like we find in Hawaii. Except that in Hawaii, if you pick up a rock, it's likely to be maybe 100 years, or maybe it's a year old, or maybe it formed last week. But on the Moon, it's likely to be 3.5 billion years old. With binoculars, you'll start to see some of the surface features. In particular, you can see some of the Moon's largest craters. The craters tell you that the Moon was the victim of some cosmic target practice. You can see that the Moon was a pretty violent place when the planets were forming. Each one of those craters is the result of an impact that was so violent it dwarfs any atomic weapons we have on Earth.
The next question one might ask is why doesn't the Earth show the same kind of scars. Well, it does have a few, like Meteor Crater in Arizona. But most of the impact craters on the Earth were erased by the forces of wind and rain and the shifting continents, including mountain-building events and volcanism. But the Moon is pretty much untouched for the last 3 billion years, so it's kind of like a museum for that violent era. If you have a good telescope, you can start to look the details of craters. Some of the big craters have walls that look terraced like a staircase, and this is because right after the crater was blasted out of the Moon's crust, the rock that formed the walls of the crater was fractured by the impact and slumped down, or collapsed, to form a series of stair steps. Many of these large craters have flat floors covered with fairly dark rock that look somewhat like seas or ponds. This is actually impact melt, which is material that had been melted by the giant impact and then rained back down into the crater and cooled. If you look in the middle of many of these large craters, you'll see some very large mountains sticking up. It's hard to tell how big these things are when you're looking through a telescope, but you can rest assured that these mountains are thousands of feet high. These are called central peaks, and they formed when the crust rebounded after the impact. There are craters all over the Moon in various stages of preservation. Many are much more beaten up, and have craters on top of craters. But the youngest craters have what look like rays of bright material coming from them. These rays are made of ejecta that were blasted out of the crust when the crater formed and sprayed across the landscape. The best example is the crater Tycho, which is in the southern highlands. It's one of the best-preserved large impact craters on the Moon. You can see its ray pattern across much of the Moon's near side with binoculars, or sometimes even with the naked eye if you've got good eyes. Finally, the dark lava seas are themselves filling in giant impact craters that are called impact basins. These basins can be hundreds of miles (kilometers) across. Mare Imbrium is one such giant impact basin. You can still see its round shape. The basins are places where absolutely gigantic impacts took place. If they had been much bigger, they could have broken the Moon apart. Through a telescope or binoculars, you'll also see that the Moon has a grayish-tan color. It's a very subtle shade. And it is exactly the color that the astronauts described when they went there. So you can actually get a little sense of what they saw by looking at the Moon yourself.
To the unaided eye, the Moon's surface appears mottled with irregular patches of gray amid splashes of white. These darker patches are known as maria, Latin for seas, since that is how they appeared to early skywatchers. We know them now as areas where lava pooled on the lunar surface billions of years ago, probably after an asteroid punched through the thin lunar crust. Together, the light and dark regions arrange themselves into the popular face of the "Man in the Moon." They were interpreted as a "rabbit in the Moon" by the Maya and Aztecs of ancient Mexico, as well as the Mimbres Indians of the southwestern United States. The Moon preserves a record of the pummeling it took 4.1 to 3.8 billion years ago. Earth got nailed by even more space rocks back then, but the planet swallowed the evidence by recycling it into the interior over the eons. As sublime as the Moon appears to the eye, a pair of binoculars turns this marbled world into a breathtaking wonder. One of the best times to look at the Moon with any optical aid is during its crescent and quarter phases. At that time, the low, slanting angle of the rising Sun creates deep dark shadows in valleys and crater floors that contrast sharply with bright mountain ranges and crater rims. When the Moon is full, it is essentially "noontime" there, with the Sun overhead. Though this geometry makes the Moon appear very bright as seen from Earth, it lowers the contrast of the lunar features. With a small telescope, a number of prominent lunar features may be observed at first or last quarter. Some of these may also be seen when the Moon is full, but as mentioned, their contrast will be significantly reduced. Moreover, the Moon is so bright that even at first or last quarter it can dazzle the eye (never mind its glaring appearance at full phase!).
Let's begin by considering the Moon's prominent features at first quarter: Near the upper eastern (right) limb (as the Moon appears to the naked eye and in binoculars), is the round, dark basin known as Mare Crisium. This region can be seen standing in the full glare of the Sun during the early crescent stages. Our perspective of Crisium on the curve of the Moon's limb often gives it an oval appearance. To the west (left) lies Mare Tranquillitatis, the region of the first manned lunar landing. (By the way, none of the Apollo landing bases can be detected in telescopes from Earth.) Above and slightly to its left is another round basin, Mare Serenitatis, which stands partly in shadow. Serenitatis is rimmed on its western (or left) edge by great mountain chains. Along the terminator, which is the dividing line between the lit and unlit regions of the Moon, many craters stand out in sharp light and shadow. Most prominent is the trio Theophilus, Cyrillus, and Catharina, all lying just below center. Theophilus and Cyrillus are actually overlapping and look like a figure 8. Catharina lies a little below them. Another prominent crater, Aristoteles, lies along the upper terminator, near the Moon's North Pole. Near first quarter it has a bright west rim, with the floor in deep shadow. Lined up neatly along the terminator at first quarter, just below the lunar equator, are three prominent walled plains. Ptolemaeus lies furthest north (uppermost) and has a number of craters and pits within it. Adjoined to Ptolemaeus to the south, and slightly smaller, is Alphonsus, site of the robotic Ranger 9 landing in March 1965. Finally, just below Alphonsus, is Arzachel, a very conspicuous crater with terraced clefts along its rim and a prominent central peak.
At last quarter, the western (or left) half of the Moon is lit. One of the more prominent features is Oceanus Procellarum in the upper left quadrant, a sprawling expanse of dark basalt punctuated by the white chalk-like streak of Aristarchus, a very recent impact crater. Observers with telescopes have reported unusual brightness and color changes in this feature, which are considered to be attributable to gas emissions from within the crust. Further east (right) is Mare Imbrium, a large, round basin that makes up one of the "eyes" of the Man in the Moon. Two bright ray craters, Copernicus and Kepler, lie near the equator in this section. The rays are produced by material ejected when an asteroid or comet struck the surface, splashing out bright fresh material from below. Mare Nubium lies directly below, or south, of Imbrium in the Moon's southern hemisphere. Mare Humorum, one of the smallest of the maria, lies to the west, or left. Most of the Moon's southern hemisphere is rugged and pockmarked with craters, including the bright ray crater Tycho. To its south lies Clavius, one of the most dominant walled plains in this sector of the Moon. Its rim and floor are pitted with a variety of craters. You don't have to wait until the Moon is full to appreciate our closest celestial neighbor. As lifeless as it appears in binoculars or a telescope, the shadow show at quarter phase imparts a dynamic quality to the lunar craggy surface. All at once, the Moon ceases to be a beautiful bauble floating over Earth's landscape and becomes a world unto its own.
TOP 10 MOON FACTS
NUMBER 1 - Bye bye Moon: 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.
NUMBER 2 - Ocean tug: Tides on Earth are caused mostly by the Moon (the Sun has a smaller effect). Here's how it works: The Moon's gravity pulls on Earth's oceans. High tide aligns with the Moon as Earth spins underneath. Another high tide occurs on the opposite side of the planet because gravity pulls Earth toward the Moon more than it pulls the water. At full Moon and new Moon, the Sun, Earth and Moon are lined up, producing the higher than normal tides (called spring tides, for the way they spring up). When the Moon is at first or last quarter, smaller neap tides form. The Moon's 29.5-day orbit around Earth is not quite circular. When the Moon is closest to Earth (called its perigee), spring tides are even higher, and they're called perigean spring tides. All this tugging has another interesting effect: Some of Earth's rotational energy is stolen by the Moon, causing our planet to slow down by about 1.5 milliseconds every century.
NUMBER 3 - The Moon is a planet?: Our Moon is bigger than Pluto. And at roughly one-fourth the diameter of Earth, some scientists think the Moon is more like a planet. They refer to the Earth-Moon system as a "double planet." Pluto and its moon Charon are also called a double-planet system by some.
NUMBER 4 - Moonquakes: Apollo astronauts used seismometers during their visits to the Moon and discovered that the gray orb isn't a totally dead place, geologically speaking. Small moonquakes, originating several miles (kilometers) below the surface, are thought to be caused by the gravitational pull of Earth. Sometimes tiny fractures appear at the surface, and gas escapes. Scientists say they think the Moon probably has a core that is hot and perhaps partially molten, as is Earth's core. But data from NASA's Lunar Prospector spacecraft showed in 1999 that the Moon's core is small -- probably between 2 percent and 4 percent of its mass. This is tiny compared with Earth, in which the iron core makes up about 30 percent of the planet's mass
NUMBER 5 - Egghead: The Moon is not round (or spherical). Instead, it's shaped like an egg. If you go outside and look up, one of the small ends is pointing right at you. And the Moon's center of mass is not at the geometric center of the satellite; it's about 1.2 miles (2 kilometers) off-center.
NUMBER 6 - Sister moons: The Moon is Earth's only natural satellite. Right? Maybe not. In 1999, scientists found that a 3-mile- (5-kilometer-) wide asteroid may be caught in Earth's gravitational grip, thereby becoming a satellite of our planet. Cruithne, as it is called, takes 770 years to complete a horseshoe-shaped orbit around Earth, the scientists say, and it will remain in a suspended state around Earth for at least 5,000 years.
NUMBER 7 - Punching bag: The Moon's heavily cratered surface is the result of intense pummeling by space rocks between 4.1 billion and 3.8 billion years ago. The scars of this war, seen as craters, have not eroded much for two main reasons: The Moon is not geologically very active, so earthquakes, volcanoes and mountain-building don't destroy the landscape as they do on Earth; and with virtually no atmosphere there is no wind or rain, so very little surface erosion occurs.
NUMBER 8 - Moon trees: More than 400 trees on Earth came from the Moon. Well, okay: They came from lunar orbit. Okay, the truth: In 1971, Apollo 14 astronaut Stuart Roosa took a bunch of seeds with him and, while Alan Shepard and Edgar Mitchell were busy sauntering around on the surface, Roosa guarded his seeds. Later, the seeds were germinated on Earth, planted at various sites around the country, and came to be called the Moon trees. Most of them are doing just fine.
NUMBER 9 - Locked in orbit: Perhaps the coolest thing about the Moon is that it always shows us the same face. Since both the Earth and Moon are rotating and orbiting, how can this be? Long ago, the Earth's gravitational effects slowed the Moon's rotation about its axis. Once the Moon's rotation slowed enough to match its orbital period (the time it takes the Moon to go around Earth) the effect stabilized. Many of the moons around other planets behave similarly. What about phases? Here's how they work: As the Moon orbits Earth, it spends part of its time between us and the Sun, and the lighted half faces away from us. This is called a new Moon. (So there's no such thing as a "dark side of the Moon," just a side that we never see.) As the Moon swings around on its orbit, a thin sliver of reflected sunlight is seen on Earth as a crescent Moon. Once the Moon is opposite the Sun, it becomes fully lit from our view -- a full Moon.
NUMBER 10 - Making of the Moon: The Moon was created when a rock the size of Mars slammed into Earth, shortly after the solar system began forming about 4.5 billion years ago, according to the leading theory.
NUMBER 2 - Ocean tug: Tides on Earth are caused mostly by the Moon (the Sun has a smaller effect). Here's how it works: The Moon's gravity pulls on Earth's oceans. High tide aligns with the Moon as Earth spins underneath. Another high tide occurs on the opposite side of the planet because gravity pulls Earth toward the Moon more than it pulls the water. At full Moon and new Moon, the Sun, Earth and Moon are lined up, producing the higher than normal tides (called spring tides, for the way they spring up). When the Moon is at first or last quarter, smaller neap tides form. The Moon's 29.5-day orbit around Earth is not quite circular. When the Moon is closest to Earth (called its perigee), spring tides are even higher, and they're called perigean spring tides. All this tugging has another interesting effect: Some of Earth's rotational energy is stolen by the Moon, causing our planet to slow down by about 1.5 milliseconds every century.
NUMBER 3 - The Moon is a planet?: Our Moon is bigger than Pluto. And at roughly one-fourth the diameter of Earth, some scientists think the Moon is more like a planet. They refer to the Earth-Moon system as a "double planet." Pluto and its moon Charon are also called a double-planet system by some.
NUMBER 4 - Moonquakes: Apollo astronauts used seismometers during their visits to the Moon and discovered that the gray orb isn't a totally dead place, geologically speaking. Small moonquakes, originating several miles (kilometers) below the surface, are thought to be caused by the gravitational pull of Earth. Sometimes tiny fractures appear at the surface, and gas escapes. Scientists say they think the Moon probably has a core that is hot and perhaps partially molten, as is Earth's core. But data from NASA's Lunar Prospector spacecraft showed in 1999 that the Moon's core is small -- probably between 2 percent and 4 percent of its mass. This is tiny compared with Earth, in which the iron core makes up about 30 percent of the planet's mass
NUMBER 5 - Egghead: The Moon is not round (or spherical). Instead, it's shaped like an egg. If you go outside and look up, one of the small ends is pointing right at you. And the Moon's center of mass is not at the geometric center of the satellite; it's about 1.2 miles (2 kilometers) off-center.
NUMBER 6 - Sister moons: The Moon is Earth's only natural satellite. Right? Maybe not. In 1999, scientists found that a 3-mile- (5-kilometer-) wide asteroid may be caught in Earth's gravitational grip, thereby becoming a satellite of our planet. Cruithne, as it is called, takes 770 years to complete a horseshoe-shaped orbit around Earth, the scientists say, and it will remain in a suspended state around Earth for at least 5,000 years.
NUMBER 7 - Punching bag: The Moon's heavily cratered surface is the result of intense pummeling by space rocks between 4.1 billion and 3.8 billion years ago. The scars of this war, seen as craters, have not eroded much for two main reasons: The Moon is not geologically very active, so earthquakes, volcanoes and mountain-building don't destroy the landscape as they do on Earth; and with virtually no atmosphere there is no wind or rain, so very little surface erosion occurs.
NUMBER 8 - Moon trees: More than 400 trees on Earth came from the Moon. Well, okay: They came from lunar orbit. Okay, the truth: In 1971, Apollo 14 astronaut Stuart Roosa took a bunch of seeds with him and, while Alan Shepard and Edgar Mitchell were busy sauntering around on the surface, Roosa guarded his seeds. Later, the seeds were germinated on Earth, planted at various sites around the country, and came to be called the Moon trees. Most of them are doing just fine.
NUMBER 9 - Locked in orbit: Perhaps the coolest thing about the Moon is that it always shows us the same face. Since both the Earth and Moon are rotating and orbiting, how can this be? Long ago, the Earth's gravitational effects slowed the Moon's rotation about its axis. Once the Moon's rotation slowed enough to match its orbital period (the time it takes the Moon to go around Earth) the effect stabilized. Many of the moons around other planets behave similarly. What about phases? Here's how they work: As the Moon orbits Earth, it spends part of its time between us and the Sun, and the lighted half faces away from us. This is called a new Moon. (So there's no such thing as a "dark side of the Moon," just a side that we never see.) As the Moon swings around on its orbit, a thin sliver of reflected sunlight is seen on Earth as a crescent Moon. Once the Moon is opposite the Sun, it becomes fully lit from our view -- a full Moon.
NUMBER 10 - Making of the Moon: The Moon was created when a rock the size of Mars slammed into Earth, shortly after the solar system began forming about 4.5 billion years ago, according to the leading theory.
LUNACY AND THE FULL MOON
Do people go crazy on the full moon? It's an enduring bit of folk wisdom, spurred by modern-day rumors that emergency rooms fill up, oddballs act odder, and dogs howl in the streets when the moon beams. Furthermore, there are lots of perfectly rational people who will assure you they just feel a little restless around the time of the full moon. The very word "lunatic" is built on the Latin word for moon, luna. So, is there proof? Biologists, psychologists, even a dentist, have taken a crack at correlating full moons with foolishness. The results have been mixed, and mysterious: A 1983 study of calls to a poison center found that unintentional poisoning increases at the full moon; and that suicide attempts and drug abuse increase with the new moon. A 1980 study, though, couldn't link drug overdose to any lunar phase. A 1991 study found that women in a treatment center who were developmentally delayed misbehaved more often on the full moon. But a 1994 study found no full-moon correlation with admissions to a psychiatric hospital, and a 1997 study said doctors see no increase of depressed and anxious patients. A study of a suburban hospital's emergency room concluded the full moon brought no howling hoards. A study of workplace absenteeism actually found more people at work on the full moon. Another inquiry revealed that people ate 8 percent bigger meals and drank 26 percent less alcohol on full-moon days than on new-moon days.
One man, a dentist at the University of Pittsburgh, took this whole business seriously enough to examine the cosmological underpinnings of the whole debate: What possible excuse would a full moon have for working mental mischief? To understand what a full moon actually is, draw a small circle on a piece of paper, and put Africa in it so you'll know it's the Earth. Draw another circle (the moon's 29.5-day orbit) around the Earth, and make a bead on each compass point. Off to the right, draw a beaming sun. Blacken the left half of each moon-bead and leave the halves facing the sun white. Your right bead is the new moon, its dark back to us. Your left bead is the full moon, its entire, sunny face visible. The upper and lower beads are hatchet-lit half-moons. Frankly, the full moon's most obvious feature doesn't look very incriminating: An extra bit of reflected sunlight is making us cuckoo? Next theory, please. Both the moon and Sun have a gravitational effect on the Earth. When they're both on our right (new moon), their combined forces tug up big ocean tides; when we come between them (full moon), they pull opposite each other. So if it's a gravitational alteration that's making us nuts, we should be looking at the new moon as well as the full moon, says Dr. Daniel Myers, the dentist who has studied the effects of gravity on migraine headaches. "I'm not saying there's no full-moon effect," he says. "It's just not caused by gravity." What else could it be? I found no study that looked closely at moonlight, its potential for disrupting sleep, or its facilitation of night-time misbehavior. It might be interesting to compare cloud-covered full moons to clear full moons, with respect to one loony behavior. And speaking of loony, when the word first appeared in the language, it was used interchangeably with "luny." This suggests that the word evolved from the older word, "lunacy" and the moon, rather than from "loon," the name of the spotted bird with the demented voice. A British study of hospital admissions for self-poisoning found that women make up 60 percent of patients at the new moon; but only 45 percent on the full moon. Hence, the study concludes, "the full moon is protective for women."
ONCE IN A BLUE MOON!
Although a full moon may look like an ordinary full moon, it may actually be a bit extraordinary-because it is a blue moon.
There are actually two definitions for a blue moon. According to the first and more recent definition, a blue moon is the second full moon in a calendar month, a phenomenon that occurred twice in 1999, as there were two full moons in both January and March (and none in February). In 2001 there are two full moons in November, and the full moon of Nov. 30 is the blue moon.
The Other Kind of Blue Moon: An older rule for the blue moon comes from the Maine Farmer's Almanac and dates back to the early 19th century. According to this definition, the blue moon is the third full moon in a season that has four full moons. The last time this type of blue moon occurred was February, 2000.
Occurrences of blue moons are not all that rare, especially given that there are two definitions for the term. Over the next twenty years there will be a total of 17 blue moons, with an almost equal number of both types occurring. No blue moon will occur at all in the years 2003, 2006, 2011, 2014, and 2017.
The more recent phenomenon, where the blue moon is considered to be the second full moon in a calendar month, last occurred in March 1999. It then happened in November 2001 and then not again until July 2004. Two full moons in one month may occur in any month out of the year except for February, which is shorter than the lunar cycle. The other, older blue moon event, which happens when there are four full moons in a season, last occured on February 2001, and will not happen again until November of 2002. Since this type of blue moon is reckoned according to the seasons, it can only occur in February, May, August, or November, about a month before the equinox or the solstice.
Since blue moons seem to occur relatively often, where does the expression once in a blue moon, meaning "rarely," come from? Actually, "blue moon" appears to have been a colloquial expression long before it developed its calendrical senses. According to the Oxford English Dictionary, the first reference to a blue moon comes from a proverb recorded in 1528. Saying the moon was blue was equivalent to saying the moon was made of green (or cream) cheese; it indicated an obvious absurdity. In the 19th century, the phrase until a blue moon developed, meaning "never." At about this point "blue moon" appears to have been used to describe the first lunar phenomenon, which only seldom occurred. It is perhaps through association with the lunar event that the phrase "once in a blue moon" today has come to mean "every now and then" or "rarely."
Do people go crazy on the full moon? It's an enduring bit of folk wisdom, spurred by modern-day rumors that emergency rooms fill up, oddballs act odder, and dogs howl in the streets when the moon beams. Furthermore, there are lots of perfectly rational people who will assure you they just feel a little restless around the time of the full moon. The very word "lunatic" is built on the Latin word for moon, luna. So, is there proof? Biologists, psychologists, even a dentist, have taken a crack at correlating full moons with foolishness. The results have been mixed, and mysterious: A 1983 study of calls to a poison center found that unintentional poisoning increases at the full moon; and that suicide attempts and drug abuse increase with the new moon. A 1980 study, though, couldn't link drug overdose to any lunar phase. A 1991 study found that women in a treatment center who were developmentally delayed misbehaved more often on the full moon. But a 1994 study found no full-moon correlation with admissions to a psychiatric hospital, and a 1997 study said doctors see no increase of depressed and anxious patients. A study of a suburban hospital's emergency room concluded the full moon brought no howling hoards. A study of workplace absenteeism actually found more people at work on the full moon. Another inquiry revealed that people ate 8 percent bigger meals and drank 26 percent less alcohol on full-moon days than on new-moon days.
One man, a dentist at the University of Pittsburgh, took this whole business seriously enough to examine the cosmological underpinnings of the whole debate: What possible excuse would a full moon have for working mental mischief? To understand what a full moon actually is, draw a small circle on a piece of paper, and put Africa in it so you'll know it's the Earth. Draw another circle (the moon's 29.5-day orbit) around the Earth, and make a bead on each compass point. Off to the right, draw a beaming sun. Blacken the left half of each moon-bead and leave the halves facing the sun white. Your right bead is the new moon, its dark back to us. Your left bead is the full moon, its entire, sunny face visible. The upper and lower beads are hatchet-lit half-moons. Frankly, the full moon's most obvious feature doesn't look very incriminating: An extra bit of reflected sunlight is making us cuckoo? Next theory, please. Both the moon and Sun have a gravitational effect on the Earth. When they're both on our right (new moon), their combined forces tug up big ocean tides; when we come between them (full moon), they pull opposite each other. So if it's a gravitational alteration that's making us nuts, we should be looking at the new moon as well as the full moon, says Dr. Daniel Myers, the dentist who has studied the effects of gravity on migraine headaches. "I'm not saying there's no full-moon effect," he says. "It's just not caused by gravity." What else could it be? I found no study that looked closely at moonlight, its potential for disrupting sleep, or its facilitation of night-time misbehavior. It might be interesting to compare cloud-covered full moons to clear full moons, with respect to one loony behavior. And speaking of loony, when the word first appeared in the language, it was used interchangeably with "luny." This suggests that the word evolved from the older word, "lunacy" and the moon, rather than from "loon," the name of the spotted bird with the demented voice. A British study of hospital admissions for self-poisoning found that women make up 60 percent of patients at the new moon; but only 45 percent on the full moon. Hence, the study concludes, "the full moon is protective for women."
Although a full moon may look like an ordinary full moon, it may actually be a bit extraordinary-because it is a blue moon.
There are actually two definitions for a blue moon. According to the first and more recent definition, a blue moon is the second full moon in a calendar month, a phenomenon that occurred twice in 1999, as there were two full moons in both January and March (and none in February). In 2001 there are two full moons in November, and the full moon of Nov. 30 is the blue moon.
The Other Kind of Blue Moon: An older rule for the blue moon comes from the Maine Farmer's Almanac and dates back to the early 19th century. According to this definition, the blue moon is the third full moon in a season that has four full moons. The last time this type of blue moon occurred was February, 2000.
Occurrences of blue moons are not all that rare, especially given that there are two definitions for the term. Over the next twenty years there will be a total of 17 blue moons, with an almost equal number of both types occurring. No blue moon will occur at all in the years 2003, 2006, 2011, 2014, and 2017.
The more recent phenomenon, where the blue moon is considered to be the second full moon in a calendar month, last occurred in March 1999. It then happened in November 2001 and then not again until July 2004. Two full moons in one month may occur in any month out of the year except for February, which is shorter than the lunar cycle. The other, older blue moon event, which happens when there are four full moons in a season, last occured on February 2001, and will not happen again until November of 2002. Since this type of blue moon is reckoned according to the seasons, it can only occur in February, May, August, or November, about a month before the equinox or the solstice.
Since blue moons seem to occur relatively often, where does the expression once in a blue moon, meaning "rarely," come from? Actually, "blue moon" appears to have been a colloquial expression long before it developed its calendrical senses. According to the Oxford English Dictionary, the first reference to a blue moon comes from a proverb recorded in 1528. Saying the moon was blue was equivalent to saying the moon was made of green (or cream) cheese; it indicated an obvious absurdity. In the 19th century, the phrase until a blue moon developed, meaning "never." At about this point "blue moon" appears to have been used to describe the first lunar phenomenon, which only seldom occurred. It is perhaps through association with the lunar event that the phrase "once in a blue moon" today has come to mean "every now and then" or "rarely."
