The Moon: Formation, Structure, and Exploration, Exams of Italian

Download The Moon: Formation, Structure, and Exploration and more Exams Italian in PDF only on Docsity! Earth’s Moon Introduction Would you want to take a vacation on the moon? Before you answer, think about these facts. There is no air or liquid water on the moon. Temperatures on the moon’s surface range from 100°C, the boiling point of water, to −170°C, well below freezing. To stay at a comfortable temperature and carry an air supply, the astronauts who landed on the moon had to wear bulky spacesuits. Each spacesuit had a mass of 90 kilograms, about as much as the astronaut himself! Because the moon’s gravity is only about one-sixth as strong as Earth’s, however, the astronauts were able to leap about like basketball stars despite their heavy spacesuits. What do you think now? Do you still want to go? Astronaut John W. Young jumps up from the moon’s surface as he salutes the flag on April 21, 1972. The machine on the left is the Apollo 16 lunar lander. The Structure and Origin of the Moon The moon is 3,476 kilometers in diameter, a little less than the distance across the United States. This diameter is only one-fourth Earth’s diameter. However, the moon containss only one-eightieth as much mass as Earth. Though Earth has a very dense core, the outer layers are less dense. The moon’s average density is about the same as the density of Earth’s outer layers. People have long wondered how the moon formed. Scientists have suggested many possible hypotheses. For example, did Earth at one time spin so fast that the material the moon is made of was thrown off? Was the moon formed elsewhere in the solar system and captured by Earth’s gravitational pull as it came near? Was the moon formed near Earth at the same time that Earth formed? Scientists have found reasons to reject all of these ideas. The theory of the moon’s origin that best fits the evidence is called the collision theory. About 4.5 billion years ago, when Earth was very young, an object at least as large as Mars collided with Earth. Material from the object and Earth’s outer layers was thrown into orbit around Earth. Eventually, this material combined to form the moon. The Size of the Moon The diameter of the moon is a little less than the distance across the United States. Looking at the Moon From Earth For thousands of years, people could see shapes on the surface of the moon, but didn’t know what caused them. The ancient Greeks thought that the moon was perfectly smooth. It was not until about 400 years ago that scientists could study the moon more closely. In 1609, the Italian astronomer Galileo Galilei heard about a device that made distant objects appear closer. Galileo soon made his own telescope by putting two lenses in a wooden tube. The lenses focused the light coming through the tube, making distant objects seem closer. When Galileo pointed his telescope at the moon, he was able to see much more detail than anyone had ever seen before. Features on the moon’s surface include craters, highlands, and Maria. Galileo saw that much of the moon’s surface is covered with round pits called craters. Some craters are hundreds of kilometers across. For 300 years, scientists thought that volcanoes had made the craters on the moon. But about 50 years ago, scientists concluded that the craters on the moon were caused by the impacts of meteoroids, rocks from space. Galileo inferred that some of the other features he saw were highlands, or mountains. The peaks of the highlands and the rims of the craters cast dark shadows, which Galileo could see. The moon’s surface also has dark, flat areas, which Galileo called Maria (mah ree uh), the Latin word for “seas.” Each one is a “mare” (mah ray). Galileo thought that the Maria might be oceans. Scientists now know that there are no oceans on the moon. The Maria are low, dry areas that were flooded with molten material billions of years ago. Since you always see the same Maria from Earth, you can tell that the moon always shows the same face to Earth. Missions to the Moon “I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the moon and returning him safely to Earth.” With these words from a May 1961 speech, President John F. Kennedy launched an enormous program of space exploration and scientific research. Exploring the Moon Between 1964 and 1972, the United States and the Soviet Union sent dozens of rockets to explore the moon. Until spacecraft went to the moon, no one knew what its surface was like. Would spacecraft landing on the moon sink deep into thick dust and be lost? When Surveyor spacecraft landed on the moon, they didn’t sink in, thus showing that the surface was solid. Lunar orbiters then photographed the moon’s surface, so scientists could find a flat, safe spot for a rocket to land.