How does gravity come about? Who has figured out its origin?

Universal gravitation was discovered by Isaac Newton, who published his theory 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 magnitude of gravity, measured in Newtons, with the symbol N; G is the gravitational constant, which is the gravity of a 1 kg object with a center of mass 1 meter apart on Earth, approximately 6.67×10^-11 N·m^2/kg^2; M and m represent the masses of the two objects of different sizes that experience gravity, measured in kilograms, with the symbol kg; r is the distance between the centers of mass of the two objects that experience gravity, measured in meters, with the symbol m.

This formula means that the magnitude 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. In layman's terms, the greater the mass, the greater the gravity; and the greater the distance, the smaller the gravity, and it decays exponentially.

This formula also makes it clear that gravity is caused by mass, that is, everything in the universe, as long as it has mass, will produce gravity. But in Newtonian mechanics, mass is only the inertial mass of an object, an isolated existence unrelated to time and space. Therefore, although it has been discovered that mass produces gravity, it is impossible to explain why mass produces gravity.

Einstein solved this problem. The special theory of relativity he founded solved the problem of the unification of time and space, and proved that movement will change time and space, making time have an expansion effect and space have a contraction effect, subverting Newton's absolute view of time and space; he also proved the equivalent relationship between mass and energy, and obtained the famous mass-energy equation: E=MC^2.

Later, Einstein demonstrated in his general theory of relativity that mass causes the curvature of space-time, and that the essence of gravity is a phenomenon caused by the curvature of space-time. In this way, many mechanical errors caused by Newton's absolute view of space-time were corrected, and the root cause of gravity was found.

So why does mass cause space-time to bend? This is because space-time is like an invisible net. Of course, this net is not flat but three-dimensional. When an object with mass enters this net, it will compress the net and cause it to dent. The greater the mass and kinetic energy, the greater the dent.

Some scientists use a stretched bed sheet to represent time and space. When placing balls of different masses on the bed sheet, people will find that the larger the mass of the ball, the deeper the depression on the bed sheet, while the smaller the mass of the ball, the more it will fall into the depression. Although the bed sheet cannot represent three-dimensional time and space, it vividly illustrates that mass is the source of gravity, and the greater the mass, the greater the gravity.

This is the curvature of space-time. People call this kind of space-time curvature caused by massive celestial bodies a space-time trap or a space-time vortex. When small-mass celestial bodies approach this space-time vortex and enter the sphere of influence of the massive celestial bodies, they will tend to be sucked into the vortex, and the phenomenon that manifests is the phenomenon of mutual attraction and gravity.

Even light traveling at 300,000 kilometers per second will have its path deflected when passing through a massive celestial body. This deflection follows the vortex line of the space-time vortex. For example, when the light from a star behind the sun passes near the sun, it is bent by the sun's gravity and can be observed by us during a solar eclipse.

It was exactly 100 years ago in 1919 that British astronomer Arthur Eddington led an expedition and traveled thousands of miles to the west coast of Africa to chase a total solar eclipse. Observations confirmed the deflection of starlight passing through the sun, which was consistent with Einstein's theory of space-time curvature. He thus announced the correctness of this great theory to the world, caused a sensation in the world scientific community, and ushered in a new stage for human civilization.

Therefore, gravity is a phenomenon, the essence of which is the curvature of space-time, a phenomenon caused by the curvature of space-time caused by mass. The difference between Newton's theory and Einstein's theory is that the former discovered this phenomenon, while the latter found the root cause of this phenomenon.

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