Isaac Newton discovered universal gravitation. His theory was published in his book”Mathematical Principles of Natural Philosophy” in 1687. The law of universal gravitation is expressed as: F=GMm/r ^ 2.
Here, F is the size of gravity, in newtons, and the symbol is N; G is the gravitational constant, which is the gravitational force of 1 kilogram object on the earth with its center of mass separated by 1 meter, about 6.67 × 10^-11 N·m^2/kg^2； M and m refer to the mass of two objects of the size of gravity, with the unit of kg and the symbol of kg; R is the distance between the centroids of two objects where gravity occurs, in meters, and the symbol is m.
The meaning of this formula is that the size of gravity is proportional to the mass of the object and inversely proportional to the square of the distance between the two objects where gravity occurs. Generally speaking, the greater the mass, the greater the gravity; The farther the distance is, the smaller the gravity is, and the attenuation is exponential.
This formula also makes it clear that gravity is caused by mass, that is, everything in the universe. As long as there is mass, gravity will be generated. But in Newtonian mechanics, mass is only the inertial mass of an object, and it is an isolated existence independent of time and space. So although it is found that mass can produce gravity, it cannot explain why mass can produce gravity.
Einstein solved this problem. The special theory of relativity he founded solved the problem of the unity of time and space, and demonstrated that sports can change time and space, making time have the expansion effect, and space has the scaling effect, overturning Newton’s absolute space-time view; Moreover, the equivalence relationship between mass and energy is demonstrated, and the famous mass and energy equation is obtained: E=MC ^ 2.
Later, Einstein demonstrated in the general theory of relativity that mass will lead to the bending of space-time, and the essence of gravity is the phenomenon caused by the bending of space-time. In this way, we not only corrected many mechanical errors caused by Newton’s absolute space-time view, but also found the origin of gravity.
So why does mass lead to space-time bending? This is because space-time is like an invisible big net. Of course, this net is not planar but three-dimensional. When a mass object enters the big net, it will press the big net to sag. The greater the mass and movement energy, the bigger the sag.
Some scientists use a stretched sheet to represent time and space. Put various balls of different mass and size on the sheet, and people will find that the larger the ball will press deeper depression on the sheet, while the smaller the ball will fall close to the depression. Although the bed sheet cannot show three-dimensional space-time, it vividly shows that mass is the source of gravity, and the greater the mass, the greater the gravity.
This is the space-time warp. People call the space-time warp caused by the massive celestial body as the space-time trap or the space-time vortex. When the low-mass celestial body approaches the space-time vortex and enters the sphere of influence of the massive celestial body, there will be a tendency to be sucked into the vortex. The manifestation is the universal gravitation phenomenon of mutual attraction.
Even the light of 300000 kilometers per second will deflect when it passes through a massive celestial body. This deflection is just along the vortex loop of the space-time vortex. For example, when the light of the star behind the sun passes near the sun, it will be bent by the sun’s gravity, and will be observed by us during the solar eclipse.
This is exactly 100 years ago, in 1919, the British astronomer Arthur Eddington led an expedition to the west coast of Africa to pursue a total solar eclipse. The observation confirmed that the deflection of starlight through the sun was consistent with Einstein’s theory of space-time bending, thus announcing the correctness of this great theory to the world, causing a sensation in the world’s scientific community, and allowing human civilization to enter a new stage.
Therefore, gravity is a phenomenon, which is the bending of space-time in essence, and is a phenomenon formed by the bending of space-time caused by mass. The difference between Newton’s theory and Einstein’s theory is that the former discovered this phenomenon, and the latter found the root of this phenomenon.
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