2023-10-20 23:34:08
Everyone on earth knows 24 hours a day. But what you don’t know is that a long, long, long time ago, there were only 5 hours in a day on earth (not enough to get a good night’s sleep). At that time, the moon was very close to the earth, like a huge silver sphere hanging in the sky. It all starts with a series of violent planet collisions. According to current academic opinion, like many galaxies in our solar system, Earth and its neighbors have survived a series of collisions. Each planet has its own collision history, resulting in unique chemical makeup and orbital characteristics. For example, Mercury is likely to have had a collision with another star, which is regarding 1/5 the size of Mercury. Most of the rock layers on the surface of Mercury were stripped away, leaving only a seemingly huge core. The violent wobble of Mars’ axis (tilt from 0° to 60° over the course of millions of years) was also caused by collisions, as was Venus’ anomalous reverse rotation. Even the outer planets—the gas giants like Saturn and Jupiter and the icy giants like Uranus and Neptune—have a history of showing signs of violence. This “marble play” caused the planet to shake and rotate violently, and the Earth’s axis was tilted due to the collision. Unlike other planets, the Earth’s tilt is both suitable and stable. A long time ago, the earth had a twin brother-scientists named it “Theia”. Theia is estimated to be regarding half the diameter of Earth (regarding the same size as Mars), and for millions of years the two planets appeared to orbit the sun in the same orbit. However, the distance between the two giant planets is too close, which means a collision is inevitable. So, regarding 4.4 billion years ago, their orbits intersected, and it was a fight between the planets: Theia was destroyed, and most of its fragments were swallowed up by the Earth. The remaining powdery debris swirled in space, mixing with fragments stripped off the Earth’s surface to form clouds that eventually condensed to form today’s moon. The birth of the moon is perhaps the most important event in the history of the earth. The collision that formed the Moon was not the last big collision that the Earth would experience, but it seems certain that it would be the last collision between the Earth and a planet. Currently, the Earth is essentially fully formed. The large amount of debris from Theia caused the Earth to expand rapidly, increasing the volume of the Earth’s core by regarding 20%. The gravity of the entire Earth was enough to attract a thick atmosphere. Most of the rocky planets in the solar system are still unable to attract atmospheres, and only Earth has gained this right. There are other significant effects. In its early stages of formation, the Moon was very close to the Earth, like a huge silver sphere hanging in the sky. Its gravitational pull caused the Earth to spin faster, making the Earth’s day last only five hours. As a result, the tilt of the Earth’s axis is more stable than before, because the increased number of rotations at the top of the spin axis prevents the planet from tilting too much. If it were not for the Moon, the pull of the solar system’s giant planets would cause the Earth’s ecliptic tilt to vary from 0 to 80°, occasionally tilting the Earth enough to make the poles warmer than the tropics. If such a drastic climate change occurs, the earth will be uninhabitable by humans, just like its two brothers-Mars and Venus. The moon has become Earth’s climate regulator. Without the moon’s stabilizing influence and tidal gravity, life might not even exist on Earth. Still, these life-making forces are waning as our planetary neighbor drifts farther and farther away. Over billions of years, the moon has been getting further and further away from the earth, and is still receding at a rate of regarding 3.8 centimeters per year. This means that the Earth’s early erratic tilt will slowly reappear, but it will only take a long enough time to exceed most people’s imagination. I wonder how long a day will be by then? How are people on earth doing? 【references】[1]P. Daniels & H. Schneider. Rediscovering the Solar System: National Geographic’s Ultimate Exploration Guide[M].Nanjing: Jiangsu Phoenix Science and Technology Press, 2022:176.[2]Wu Weiren, Gong Zizheng, Tang Yuhua, etc. Research on risk response strategies for near-Earth asteroid impact[J].Chinese Engineering Science, 2022,24(02):140-151.[3]The Moon: Earth’s satellite full of mysteries[J].China Science and Technology Awards, 2016 (09): 76.[4] https：//www. sohu. com/a/631236520_100146324
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