The universe is a vast and boundless space, which contains countless galaxies, stars, planets and other celestial bodies. The formation and evolution of the universe is a complex and magical process, which involves the knowledge of physics, astronomy, chemistry and other disciplines. In this article, we will introduce the composition and structure of the universe from the basic elements, basic forces, elements and matter of the universe. We will then introduce the most widely accepted theory of the origin and evolution of the universe in the scientific community, the Big Bang theory, and the key stages in the evolution of the universe described by this theory. Finally, we will point out that there are still many unknowns about the origin and evolution of the universe that we need to continue to explore and study.
First, let's look at what the universe is made of. According to Einstein's theory of relativity, energy and matter can be converted into each other, so it can also be said that there are three basic elements in the universe, namely time, space, and energy (or matter). Time refers to the sequence in which events occur, space refers to the location and scope of the existence of an object, and energy refers to the ability of an object to move or change. Matter refers to an entity composed of atoms or molecules. In the universe, there are close connections and influences between time, space, and energy (or matter).
Second, let's look at the fundamental forces at work in the universe. The basic force refers to the four most basic forces that exist in nature, which are gravity, electromagnetism, strong force and weak force. Gravity refers to the force that attracts each other between two objects with mass, electromagnetic force refers to the force that interacts between charged particles, strong force refers to the force that combines particles inside the nucleus, and weak force refers to the force that acts during the decay of some particles. These four basic forces determine the interactions and changes between substances.
Again, let's look at how many elements there are in the universe. An element is a substance composed of the same atom. Atoms are tiny particles made up of nuclei and electrons. The nucleus is made up of protons and neutrons, which in turn are made up of smaller particles, quarks. There are currently 118 known elements, of which 94 exist in nature and the remaining 24 are synthetic. Elements are arranged in a table according to their atomic number (i.e. the number of protons within the nucleus), called the periodic table.
Finally, let's look at how matter formed and evolved. Matter is made up of molecules, molecules are made up of atoms, atoms have nuclei and electrons, atomic nuclei have protons and neutrons, and protons and neutrons are made up of quarks. These particles combine or separate from each other through fundamental forces, resulting in substances of different types and states. In the process of the evolution of the universe, matter has undergone many changes from simple to complex, from disorder to order, from uniform to inhomogeneous.
Next, we will introduce the mainstream theory about the origin and evolution of the universe - the Big Bang theory. The Big Bang theory holds that the universe was originally a "primordial fireball" with extremely high temperature, high density, and high pressure, followed by an explosion that formed the universe. This theory is supported by a large amount of experimental evidence, such as the existence of cosmic microwave background radiation (CMB) and Hubble's law.
So, how did the universe evolve after the Big Bang? According to the Big Bang theory, we can divide the evolution of the universe into the following stages:
- Planck Period: This is a very brief period that occurred about 13.8 billion years ago within 10-43 seconds of the Big Bang. During this period, time begins, space appears, energy is released, and it expands at a very rapid rate. This period is very mysterious, during which the temperature reached more than 1032 kelvin (100 billion times higher than the surface temperature of the sun), the density reached more than 1096 kg/cubic meter (1077 times higher than the density of water), and the pressure reached more than 10113 Pa (10108 times higher than the pressure on the Earth's surface). During this period, all four fundamental forces were unified into a single force, and a variety of energetic particles were produced.
- Inflation: This is a very brief period of 10-35 seconds to 10-32 seconds after the Planck period about 13.8 billion years ago. During this period, a mysterious and powerful force arose under some unknown mechanism - the skyrocketing field. The inflationary field has negative pressure and can produce anti-gravity effects, causing the universe to expand rapidly about 1078 times faster than the speed of light. This process makes the space of the universe flat, uniform, and smooth, and leaves tiny density fluctuations in the universe. These density fluctuations later became the seeds for the formation of the structure of matter. During this period, gravity separates from a single force and begins to act on matter.
- Radiation-dominated period: This is a period of tens of thousands of years that occurred between 10-32 seconds and 38,000 years after the inflationary period about 13.8 billion years ago. During this period, the decay of the inflationary field into other particles and radiation led to an equilibrium between matter and radiation. During this period, the universe was in a state of high temperature, high density, high pressure, and the density of matter was very large, even exceeding the density of nucleons. During this period, the interaction between matter was very strong due to very high temperatures (up to 1032 Kelvin), resulting in various elementary particles and force fields. During this period, several important phase transitions and symmetry breaking phenomena occurred, such as strong interaction separation, electroweak interaction separation, etc.
- Material-dominated period: This is a period of hundreds of millions of years that occurred about 13.8 billion years ago between 38,000 and 370 million years after the radiation-dominated period. During this period, the equilibrium between matter and radiation was lost due to a gradual decrease in temperature (down to 109 Kelvin). During this period, matter began to dominate and began to condense into more complex structures. During this period, several important events and processes took place, such as nucleosynthesis, antimatter annihilation, recombination, re-clutch, etc.
Structural Formative Period: This is a period that occurred about 13.8 billion years ago and is still ongoing 370 million years after the period of material domination. During this period, due to a further decrease in temperature (down to 3000 Kelvin), matter and radiation are completely separated. During this period, matter began to gather under gravitational action, and various celestial bodies and structures were formed. During this period, several important events and processes took place, such as primordial star formation, galaxy formation, galaxy cluster formation, supercluster formation, etc.
Through the above combing of the evolution process of the universe, we can see that after the Big Bang, the universe has undergone countless changes and evolutions, and gradually developed from simple to complex, from disorder to orderly. Although we already know and understand a lot about the universe, there are still many unknowns that we need to explore and answer. For example:
- What was there before the Big Bang?
- What is a skyrocketing market? Why did it happen?
- How many elementary particles and force fields exist in the universe?
- How much ordinary matter, dark matter, and dark energy are in the universe?
- Does the universe have boundaries? Are there multiple worlds?
In short, exploring and understanding the universe is the eternal pursuit and dream of human beings. Only through continuous learning and research can we better understand the world we live in and enjoy it better.