The history of the moon is tragic! I used to be beaten a lot. 4.6 billion years ago, the moon was composed of gas clouds and dust. When the moon freezes, small space debris is continuously sucked in. During the period from 3.9 billion years ago to 4.2 billion years ago, this big collision period produced the pits on the surface of the moon that we see today. 3.8 billion years ago, the radioactive material in the center of the moon caused internal heating, which turned the moon into a molten state and triggered a volcanic eruption on the surface of the moon. Lava flows to the surface of the moon, and they flow to low-lying basins, forming the Moon Sea. 365.438 billion years ago, the volcanic activity period passed and the lava solidified. Except for the occasional meteor collision, the moon has become what we see today.
The interior of the moon is huge. When the spacecraft was first sent into space to fly around the moon, scientists noticed that the spacecraft unexpectedly slowed down or accelerated at some points. Scientists immediately speculated that the speed change was due to the collision between high-density meteoroids and the moon and their penetration into the molten moon. High density places generate stronger gravity around them, so the spacecraft is accelerated. The careful calculation of the motion of the lunar probe enables scientists to accurately describe the mass distribution of the invisible part of the moon.
The interior of the moon can also be studied by the seismograph left on the moon by Apollo astronauts. The detector recorded nearly 10000 lunar earthquakes. Some of them are caused by the high-speed impact of objects on the moon, but most of them are caused by the internal changes of the moon caused by the tidal force of the earth. Most lunar earthquakes occur at 640 ~ 1200 km below the surface of the moon. Below this depth is the lunar core, which most scientists think is still in a molten state. Above the lunar seismic belt are the lunar cover and the lunar shell. The average thickness of the lunar shell is only 72 kilometers.
A total of 12 astronauts walked on the surface of the moon. They landed on the moon in pairs, a total of six groups, through the Apollo program 1 1 to 17. There would have been more landing plans, but they were cancelled by the National Aeronautics and Space Administration (NASA). The hapless Apollo 13 only circled the moon several times and failed to land successfully, as described in the famous movie of the same name. Some confidential information of the Soviet Union during the Cold War showed that the Soviet Union also tried to send astronauts near the moon, but for various reasons, these plans died before implementation.
Astronauts brought back 38 1 kg (840 pounds) of matter from the moon. These substances vary in size, from heads to dust particles, and come from the vast area of the moon from plains to mountains. Among the rocks brought back, the youngest is only 3 1 100 million years old, while the oldest is 4.42 billion years old, which is close to the age of the solar system itself.
The rocks on the moon are generally older than those on the earth. The moon was geologically inactive 365,438+0 billion years ago, and many areas have been inactive. In contrast, the volcanoes on the earth were still very active at that time, and the crustal movement has never stopped until now. So most of the rocks on the earth are much younger than 3 billion years, and most of the rocks on the moon are 4 billion years or even longer. In this way, studying the rocks on the moon, not on the earth, can help us understand the early history of the solar system.
Geologists are familiar with the types of rocks brought back from the moon. Breccia is a mixture of different types of rocks "welded" together under pressure, which was discovered in valleys and highlands explored by Apollo astronauts. Most rocks found at the bottom of the valley are basalt, a granular rock containing metals and silicates.
Through the analysis of moon rocks, it can be concluded that although the moon rocks contain a large number of rare elements such as uranium and thorium, the earth and the moon are similar in chemical composition, at least on the surface. Maybe one day, mining on the moon is economically feasible.
Because the mass is much less than that of the earth, the acceleration of gravity on the surface of the moon is also much less than that of the earth. It covers one sixth of the earth's surface. A person who weighs 100 kg on the earth will weigh less than 17 kg on the moon, because the pull of the moon on people is 1/6 of the pull of the earth on people. Astronauts use a combination of walking and jumping to make themselves move on the moon as soon as possible. If it weren't for the influence of their spacesuits, they could jump six times higher and six times farther than the earth. Putting athletes in flexible clothes and hosting the Olympic Games on the moon will definitely be recorded in the Guinness Book of World Records!
Drop a hammer and a feather from the same height on the moon, and they will land on the moon at the same time. If you do this little experiment around now, it is obvious that the hammer landed first, because the ratio of feather surface area to weight is much larger than that of the hammer, and the air resistance when falling makes the feather slow down quickly. On the moon, there is no air, and the force on the hammer is greater than that on the feather, but this force just makes the hammer with large inertia and the feather with small inertia have the same acceleration. Inertia depends on the mass of the object, and it is the difficulty to make the object move or stand still. For example, the quality of Cadillac is greater than that of hockey, so it is far more difficult for Cadillac to accelerate from 0 km/s to 60 km/s than hockey, and it is also more difficult to stop. Although the force of the hammer on the moon is greater than that of the feather, it can only have the same acceleration as the feather, so the hammer and the feather will touch the moon at the same time.
Looking at the earth from the moon, you will see a "terrestrial phase" similar to the moon phase change. Just as the reason for seeing the phase change of the moon from the earth, the earth will also have a "phase change" seen from the moon. And the earth is just complementary to the moon. In other words, when we see the full moon, the astronauts on the moon will see the crescent-shaped earth; When we see the dawn of1/April, astronauts will see three-quarters of the earth. Of course, the earth seen from the moon is four times bigger than the moon seen from the earth.
An interesting phenomenon is that the moon is gradually moving away from the earth. Although the moon revolves around the earth, it leaves us at a speed of 30 cm/year.