People always think that the universe has existed in a static state for an infinite time, and will exist in this state for an infinite time. But Edwin Hubble's landmark observation in 1929 ended this concept and brought the exploration of the origin of the universe into the scientific field. Hubble found that no matter which direction you look, distant galaxies are far away from us. In other words, the universe is constantly expanding, so it should shrink to a point at the beginning. This moment is called BIGBANG moment. The density of the universe at this point is infinite, which is mathematically called singularity. All scientific theorems are invalid at this singularity. This means that all the events before this moment can't have any influence on the events after this moment, and the events after this moment can't be deduced from the events before scientific rationality. In other words, there is no causal relationship between the events before and after the Big Bang. In this way, in the physical sense of time, time starts from the BIGBANG singularity.
Second, the end of time-black hole
Stars will contract and collapse toward themselves due to gravity. When the mass of a star is greater than a certain limit, the repulsive force generated by Pauli exclusion principle can't balance the gravity, so the star will continue to collapse and form an infinite dense region which we call a "black hole". The gravity on the surface of a black hole is so strong that nothing, including light, can escape from this area and reach distant observers. This means that if a fearless astronaut collapses inward with the star, he sends a signal to the spacecraft around the star every second. If the star collapses to the critical radius at 1 1 to form a black hole, the companion on the spacecraft will not receive any signal after receiving the last signal from the astronauts on the star at 10: 59. Time is over here. People can appropriately apply the poet Dante's words about the entrance to hell to the black hole: "Those who enter here must abandon all hope."
Third,
god
How did the universe begin? -The origin and destiny of the universe
Loading American astronauts
Although people have a certain understanding of the post-Big Bang evolution, there are still some problems that have been bothering people. For example, why are all places and directions consistent in time and space? Why does the universe begin to expand at a critical expansion rate so close to the collapse and eternal expansion model? Although the universe is so uniform on a large scale, how can there be local irregularities? Or we can ask, at the moment of BIGBANG, who decided that the universe has evolved in this mode so far? In this book, Hawking describes people's difficult steps on the road to the origin of the universe. One is the origin of the universe, which is explained by anthropic principle and called chaotic boundary conditions. Just like a famous group of monkeys knocking on typewriters, most of them will be nonsense, but pure accident may make them knock out a line of Shakespeare's short poems. Similarly, among the various random possibilities of the origin of the universe, it is precisely because we live in such a smooth and consistent area that it is possible to have such a complex human being. Another explanation is called "inflation model", which holds that the universe expands at an acceleration at the beginning, and the radius of the universe increases by 1 0 trillion times (the 30th power of 10) in less than1second. Although these theories can answer some doubts in different programs, they can't determine the fundamental internal order of the universe in the end. Now people are turning to seek a complete and coordinated theory, which combines quantum mechanics with gravity. Under the guidance of this theory, people have found another model to describe the origin and fate of the universe, that is, space-time has only a limited scale, and there is no singularity as its boundary or edge. Space-time is like the earth, with limited surface area and no boundaries, but with two more dimensions. The beginning of the universe once made people imagine a creator to create the world, but if the universe is completely self-sufficient without boundaries and edges, it means that it has neither a beginning nor an end-it is existence. So, is there a place for God?
Saturnian satellite
Fourth, the unity of physics-the ultimate theory.
Humans are seeking to establish a complete and coordinated unified theory applicable to every event in the universe, in which no specific constants need to be selected to conform to the facts. Finding such a theory is called "the unity of physics", which is the primary goal of contemporary physics. Einstein spent most of his later years in this work, but he didn't succeed. People divide the forces into four kinds, namely, gravity, electromagnetic force, weak nuclear force and strong nuclear force, and unify the latter three kinds of forces through the so-called "Great Unity Theory" (GUT), and the work of bringing them into gravity is under way. The difficulty of this work is that general relativity is a "classical" theory, which does not contain the uncertainty principle of quantum theory, while other theories rely on quantum mechanics very basically. So it is necessary to combine general relativity with quantum mechanics. Although there are still some unsolved problems, we have seen the hope of success from the "string theory" that people are studying at present.