The moon is tidally locked, and the earth can only see one side of it. Will the earth be locked by the sun in the future?
The moon is tidally locked, and the earth can only see one side of it. Will the earth be locked by the sun in the future? Many people have doubts. There is also tidal locking between the earth and the sun. Why doesn’t the earth only face the sun? With so many planets and satellites in the solar system, why is only the moon tidally locked to the earth and only one side can be seen? , is this itself a coincidence?
In fact, it is not a coincidence. To put it imprecisely, all satellites have been tidally locked or gradually locked by the planets they orbit. However, due to the different physical properties of the orbit and the celestial body itself, the time required to be tidally locked varies greatly. Tens of millions of years, sometimes tens of billions of years.
In addition, although the moon has been tidally locked, there is still a "liberation motion", which means that the moon will still swing back and forth. In fact, we can see 59% of the moon's surface, not exactly 50% of the moon's surface. The earth has not been tidally locked by the sun. According to calculations, the earth will be locked by the tidal sun in more than 50 billion years. Of course, the sun will no longer exist before that.
The word "tidal locking" can explain that the earth's rotation slows down and the moon's distance from the earth is related to this. A more intuitive explanation is that over time, the earth and the moon have reached a balance, just like two gears meshing with each other, a large gear turns slowly, and a small gear turns fast.
Earth is tidally locked to the moon, and the moon is also trying to tidally lock the earth. Over billions of years, the rotation speed of the earth has changed from a few hours to the current 24 hours. This energy is transferred to the moon, making the orbit of the moon higher and higher, So far, it is still flying outward at a speed of a few centimeters per year, and the corresponding earth is turning slower and slower. Unfortunately, the result of the game between the two will be that the moon will be thrown out of the earth-moon system, and the earth will rotate at a slower speed than the current speed, so Unlike Charon, which tidally locks Pluto, the Moon's attempts to tidally lock Earth are doomed to failure.
In fact, it is very common for a satellite to be tidally locked in the solar system by a planet, but Mercury is the only case where a planet is tidally locked by the sun (and it is a 3:2 orbital resonance), because only Mercury is close enough to the sun. Between planets and satellites, stars and planets that surround each other, the gravitational effect on one of them is unbalanced. Simply put, the half that is closer to the other side receives a greater gravitational force than the half that is farther away. Affected by the difference, the volume of the side with a smaller mass will change, forming a tidal bulge towards the side with a larger mass. Satellites with a greater mass difference and closer distance will eventually be torn apart by tidal forces, forming Saturn rings, Jupiter rings, etc. wreckage.
A satellite with a suitable relative mass and a suitable distance will lead to two results under the influence of the gravitational field: one is that the rotation speed is faster than the revolution speed, and the rotation decelerates; the other is lower than the revolution speed, and the rotation speeds up, two results Both point to the tidally locked mode, that is, the tidally locked celestial body takes the same time to revolve around its partner to revolve around its own axis, and the tidally locked side can only face the other side with one side.
Tidal locking is affected by distance, mass ratio, and orbital eccentricity. Tidal locking occurs between the two at the same time, and the result is that both sides will change their rotation and revolution time. The extreme examples of this are Pluto and Pluto Because of the small difference in mass, they are tidally locked to each other, that is, Charon can never be seen from the back of Pluto, and Pluto can never be seen from the back of Charon. At the same time, the two also revolve around each other (revolution).
As for our earth, in fact, the tidal locking of the earth, the moon, and the sun is also happening slowly. From 20 hours a day 420 days a year 500 million years ago to now, the speed of the earth's rotation is slowing down (of course the actual impact There are many factors, and the friction between the atmosphere and the ocean also reduces the speed of slowing down), which means that one day in the future, the earth will be completely locked by the sun's tide, and half of the earth will not be able to see the sun.
