All celestial bodies move under the action of gravity. The so-called moon goes around the earth and the earth goes around the sun because of the gravity between the moon, the earth and the sun. Actually, gravity is mutual. Newton's law of universal gravitation and Einstein's equation of gravitational field tell us that the magnitude of gravity is determined by the mass of objects and the distance between them. The greater the mass of the object, the greater the gravity, and the farther away from each other, the gravity decreases by the square of the distance.
The formula of the law of universal gravitation is: f = GMM/R2；; Einstein's gravitational field equation is expressed as: r _ uv-1/2 * r * g _ uv = κ * t _ uv (r μ ν-(1/2) g μ ν r = 8g π t μ ν/(c * c). These two formulas seem unrelated, but they both express the same thing, that is, the law of gravitational field.
Application of Einstein Theory and Newton Theory. Newton's law of universal gravitation is defined as a classical mechanical theory, which is based on the absolute concept of time and space. But the fact is that our world is moving, and time and space will change qualitatively and move, so time and space are relative. Einstein's field theory fundamentally solved the problems of gravitational field and different temporal and spatial changes, corrected some mistakes of Newton's classical mechanics, and made people know the world more accurately. It is a higher level theory of Newton's theory of universal gravitation, which has greatly promoted the progress of human civilization.
Einstein's special theory of relativity and general theory of relativity are based on the limit of light speed and the invariability of light speed. It is believed that the movement of an object will lead to the expansion of time and space, and the mass of the object will distort time and space, which will also lead to the expansion of time and space. So time and space are different under different motion systems and different gravitations, so time and space are relative.
But this change is meaningful, especially in the state of high speed or large gravity field. At low speed and low gravity, this change is very small and difficult to be detected. In our world, most observations are made at a very low speed, and the errors caused by Newton's classical theory can be ignored, so the law of gravity has been playing a huge role.
We will not discuss the theoretical problems of the two great men today. What we want to answer is that the sun rotates around it at a low speed, so it can be explained by Newton's theory.
The moon actually revolves around the common center of mass of the earth and the moon. According to Newton's theory of gravity, the moon does not really revolve around the earth, but both the earth and the moon revolve around the common center of mass. Just because the mass of the earth is 8 1 times greater than that of the moon, the gravity is much greater than that of the moon. In this way, the center of gravity between them is definitely biased towards the earth, but not in the core, but at the place where the core connects with the lunar core, 467 1km away from the core. Both the Earth and the Moon revolve around this center of mass, and period of revolution celebrates 27.32 Earth Day.
But because this center of mass is inside the earth's surface, and the moon has been tidal locking by the earth, but the earth is not locked, and the rotation speed is very fast, so it is difficult to see that the earth and the moon revolve around each other. It seems that the moon orbits the earth once every 27.23 days. If we use precision instruments to measure, we can also measure the revolution of the earth around the center of mass of the earth and the moon.
Moreover, the earth is also affected by the tidal force of the moon, and its rotation will slow down by 15 microseconds every year, showing the trend of being tidal locking, but this time will be very long, until the solar system is destroyed, and the earth's rotation will only slow down by 2 1 hour a year. I won't say this. In short, the revolution caused by gravity is mutual.
The revolution of the earth around the sun is actually around the common center of mass of both sides. How big is the earth? Compared with the sun, it is not an order of magnitude at all. The mass of the earth is only one third of that of the sun, so the gravity of the earth is much smaller than that of the sun. The center of gravity of the attraction between the sun and the earth is also inside the sun, only 450 kilometers away from the core of the sun. Compared with the radius of 696 thousand kilometers of the sun, this distance is almost negligible, so it seems that the earth revolves around the sun completely.
But as the center of mass of the solar system, it is different. The total mass of the sun accounts for 99.86% of the whole solar system, and other celestial bodies such as Octavian account for 0. 14%. Although it is still very small, it is only 0.0003% of the mass of the sun, so that the gravity of all celestial bodies in the solar system except the sun can pull the common center of mass of the solar system away from the sun itself. Jupiter alone accounts for 0. 1% of the mass of the sun, which is the mass of all planets.
It is estimated that when all the planets move to the side of the sun and form a line, the center of mass of the solar system is at 1% astronomical unit from the solar core, that is, about 1.5 thousand kilometers from the solar core. The radius of the sun is 696,000 kilometers, so the core of the solar system is about 800,000 kilometers away from the surface of the sun.
Therefore, the earth revolves around the sun, in fact, the sun and the earth revolve around a common center of mass, and the whole solar system is also the sun and all planets, dwarf planets, satellites and other celestial bodies revolve around a common center of mass, and this center of mass is constantly changing, so it is very complicated to accurately describe this movement.
So what does the sun revolve around? The sun is a part of the Milky Way. The Milky Way has a mass of about 2 100 billion solar mass, a diameter of about 200,000 light years and about 400 billion stars. The sun is just one of the yellow dwarfs with a mass of1.9891*1030kg. A yellow dwarf refers to a star whose spectrum is mainly G-shaped and its mass is based on the sun, which is generally between 0.8- 1.4 times the mass of the sun.
The yellow dwarf is not big among all the stars, but a medium-sized star. But from the ratio of the mass of the Milky Way to the number of stars, we can see that the average mass of stars is only about half that of the sun. In this way, we can conclude that stars smaller than the sun account for the vast majority, and observations have proved this.
In the Milky Way and the whole universe, more than 80% of the stars are less than the sun. Stars whose mass is less than 0.8 times that of the sun and more than 0.08 times that of the sun are generally called red dwarfs. This kind of star has a special life span, and the smallest red dwarf can reach 1 trillion years or more.
The sun is about 26,000 light-years away from the center of the Milky Way. It sits on the Orion arm of the spiral galaxy, the Milky Way, and rotates around the center of the Milky Way with all the stars. The center of the Milky Way is the huge gravitational core of the Milky Way, and the center is a black hole with a mass of about 4.3 million times that of the sun. The sun, together with the eight planets and other celestial bodies in the solar system, rotates around the center of the Milky Way at a speed of about 250 kilometers per second, and it takes about 250 million years to make a circle.
Stars have both a general trend of revolution around the center of the Milky Way and a small trend of their own movement. Although all the stars in the galaxy revolve around the center of the galaxy, strictly speaking, the stars do not move around the center of the galaxy in a balanced and synchronous way because of various complex gravitational factors around the stars, so that each star will have its own trajectory and the distance between stars will change. However, because the distance between stars is too far, for example, the nearest star in the solar system is 4.22 light years, the trajectory of stars is extremely small compared with the distance between stars, even hundreds or even hundreds of kilometers per second.
So for our naked eyes, the stars have not changed for thousands of years, such as the Big Dipper, which has been that shape since ancient times. But it will change over time. After 654.38+ million years, the Big Dipper will no longer be in this arrangement, and its shape will change dramatically. Humans have only a few thousand years of records, and there seems to be no change between the stars they see, so they are called "stars".
Where is the center of mass of the Milky Way galaxy in this galaxy group? In the universe, all celestial bodies move under the action of gravity, and the structure of celestial bodies is layered like a Russian doll, getting bigger and bigger, all moving around the center of gravity. For example, the superior celestial structure of the Milky Way is the local galaxy group, covering the sky area of about 1000 light years. This group includes more than 50 galaxies, including Andromeda and the Milky Way. Andromeda is the boss and the Milky Way is the second. Other galaxies are relatively small and most of them belong to dwarf galaxies.
So in this galaxy group, the center of gravity is between Andromeda and the Milky Way, and other small galaxies move around these two large galaxies, becoming the satellite galaxies. The general trend is that Andromeda galaxy and the Milky Way galaxy are approaching at a speed of hundreds of kilometers per second under the action of gravity. It is predicted that three to four billion years later, these two galaxies will collide and merge into a larger elliptical galaxy, and some Pettigrew galaxies may have been eaten by the eldest brother and the second child.
The larger celestial structures in the universe are moving. Our galaxy cluster is a small member of local supercluster. The local supercluster contains hundreds of galaxy clusters, covering an area of about 654.38 billion light years. Many clusters in the local supercluster are much larger than this supercluster. For example, the core Virgo cluster has more than 2,500 galaxies, which is more than 50 times that of this supercluster. Our Milky Way and our local galaxy cluster revolve around the center of gravity of this huge local supercluster, which takes about 654.38+067 billion years.
Above the local supercluster, there is the Rania Kaya supercluster with larger structure, followed by the Pisces whale supercluster, the Si Long Great Wall structure, the Hercules-Corolla Brias Great Wall and so on. These huge structures make up the Hubble volume with a radius of 46.5 billion light years, and there is a larger and incalculable Hubble volume. All objects in the universe move under great gravity.
Besides the four basic forces, dark matter and dark energy are the dominant forces in the universe. Modern astrophysical research believes that besides gravity, there are strong, weak and electromagnetic forces that dominate the movement of the universe, and dark matter and dark energy play a leading role in the movement of the universe. These two invisible substances can account for more than 95% of the total mass energy of the universe. Dark matter dominates the formation of the cosmic structure, which shows that the cohesion of the celestial system is far greater than gravity, keeping the celestial structure from being dispersed; However, dark energy is the driving force behind the expansion of the universe and accelerates the expansion of the universe.
The contest between these two kinds of mass and energy dominates the future direction of the universe. The life span of the universe and the outcome of life and death depend on the game and result of these two forces. This is another topic. If you are interested, please refer to the related articles published in Time and Space Communication in the past. Thank you for reading and welcome to discuss.
The space station gives you a real explanation of the movement track of the solar system!
As we all know, the moon is a satellite of the earth. It goes around the earth day and night, and it can go around the earth once in almost 27 days. Our earth is one of the eight planets in the solar system, and it is also guided by the sun and moves in a spiral motion with the sun. In order to let people know the solar system intuitively, the previous textbooks described the solar system as a plane shape and thought that the eight planets all revolve around the sun. The latest scientific research results have come out. It turns out that everyone's cognition is wrong. The eight planets in the solar system do not revolve around the sun, but spiral forward with the sun under its guidance.
The solar system is at the edge of the Milky Way, at the end of the third spiral arm of the Milky Way, that is, on the spiral arm of Orion, which is a rather remote position. Tell a joke, the solar system is too far away. If aliens from extraterrestrial civilization come to the earth, it is impossible to find the earth by going the wrong way. Because in the Milky Way, there are many star systems that are bigger and brighter than the solar system, and there are only a handful.
In the solar system, its center is the sun. Although the sun is only a medium-sized star, its mass has occupied 99.85% of the total mass of the whole solar system. The rest of the mass includes planets and their satellites, planetary rings, and interplanetary substances such as asteroids, comets, Kuiper Belt objects, outer Neptune objects, theoretical Oort clouds, dust, gas and interplanetary particles, accounting for only 0.05% of the mass of the whole solar system. In the solar system, the sun is like a parent, taking care of the planets around him with its own strength, light and heat.
For this reason, the sun tightly controls all the celestial bodies around itself in the solar system with its strong gravity, making them rotate with itself in an orderly manner. At the same time, the sun and all the members of the solar system orbit around the center of the galaxy.
We usually see the solar system the most, so we all know that the moon goes around the earth and the earth goes around the sun. I would like to add here that strictly speaking, the earth does not revolve around the sun, but around the center of mass of the sun. Because the sun is so big, we seem to go around it. In fact, the center of mass of the sun is slightly shifted.
So to know what the sun goes around, we might as well zoom in, the Milky Way.
The sun is just a very common one in the galaxy. It is estimated that there are1000-400 billion stars in the Milky Way, that is, stars that shine like the sun! No wonder we usually see so many stars.
With the development of astronomy, human beings have simulated the general outline of the above picture according to observation. All the stars in the Milky Way also rotate around the same center. This center is not an ordinary star because it doesn't have such a large mass. At the center of the Milky Way is a supermassive black hole (Sagittarius A)!