What is Cosmology?

Cosmology is the study of the universe. It also studies the position of humans in the universe.

Cosmology

History

The word was originally coined by Germany

In the past, Greek philosophers believed that the sky is a celestial sphere, and the mechanical principles in it have become

Big bang theory

different

Cosmology is a discipline that studies the large-scale structure and evolution of the universe. When we look at the depths of space, we are going back in time. The farthest galaxies we've seen, it's a long, long time ago when the light they emitted began their long space travel. Since huge galaxies were once young,

Only 20 years ago, people had little confidence to answer cosmology and

To begin, we will introduce some of the principles that form the basis of any scientific universe theory.

Hubble's Law of Cosmology

The Big Bang Cosmology holds that the universe was formed by a dense and hot singularity expanding after a big bang 15 billion years ago. In 1929, the American astronomer Hubble proposed the Hubble's law that the redshift of galaxies is proportional to the distance between galaxies, and derived the theory that galaxies are expanding away from each other. The idea that the universe is not eternal but created from nothingness can be said to be deeply ingrained in Western culture. Although Greek philosophers have considered the possibility of the eternal universe, all major Western religions have consistently maintained that the universe was created by God at a specific time in the past. Like historians, cosmologists realize that the key to the future lies in the past.

Back in 1929, Edwin Hubble made a landmark discovery that no matter which direction you look, galaxies in the distance are rushing away from us. In other words, the universe is expanding. This means that earlier stars were closer to each other. In fact, it seemed that at some point between about 10 billion and 20 billion years ago, they happened to be in the same place, so Hubble's discovery hinted at a moment called the Big Bang, when the universe was infinitely close.

Around 1950, Gamow was the first to establish the idea of the Big Bang. This big bang of the creation universe is not the kind of explosion that occurred at a certain point on the earth and then spread to the surrounding air, but a kind of explosion that occurred simultaneously everywhere and filled the entire space from the beginning. That kind of explosion, every particle in the explosion leaves every other particle and rushes. In fact, it should be understood as the rapid expansion of space. "Entire space" can refer to the entire infinite universe, or a finite universe that can bend back to its original position like a sphere. According to the Big Bang Cosmology, the very early universe was a large uniform gas composed of microscopic particles, with extremely high temperature, high density, and expanding at a great rate. These gases have a uniform temperature under thermal equilibrium. This uniform temperature was an important sign of the state of the universe at that time, so it was called the temperature of the universe. The adiabatic expansion of the gas will reduce the temperature, allowing the nucleus, the atom and even the star system to appear one after another.

Cosmological universe history

Since Gamov established the concept of the Big Bang in 1948, through decades of hard work, cosmologists have sketched out such a history of the universe for us:

At the beginning of the big bang:

15-20 billion years ago, extremely small volume, extremely high density, extremely high temperature.

After the big bang:

10-43 seconds the universe emerges from the quantum background.

10-35 seconds the same field is broken down into strong, weak and gravitational.

At 10 trillion degrees in 10-5 seconds, protons and neutrons are formed.

At 100 billion degrees in 0.01 second, photons, electrons and neutrinos predominate. Proton neutrons account for only one billionth of a billion. Thermal equilibrium state, the system expands rapidly, and the temperature and density continue to decrease.

After 0.1 second, 30 billion degrees, the neutron-proton ratio decreased from 1.0 to 0.61.

Ten seconds later, 10 billion degrees, the neutrinos escaped outward, an annihilation reaction of positrons and electrons appeared, and the nuclear force was not enough to restrain neutrons and protons.

3 billion degrees after 13.8 seconds, deuterium and helium-like stable nuclei (chemical elements) were formed.

At 300 million degrees after 35 minutes, the nuclear process stopped and neutral atoms were not formed.

After 300,000 years after the Big Bang, 3,000 degrees later, chemical bonding caused neutral atoms to form. The main component of the universe was gaseous matter, and gradually condensed into denser gas clouds under the action of gravity, until the stars and the star system.

Cosmological theoretical significance

The Big Bang theory reveals a magnificent picture of the evolution of the universe. The expansion of the universe began about 20 billion years ago. This initial moment and its previous conditions are purely speculative. The early universe was very hot, dense, and perhaps very irregular. This irregularity and anisotropy gradually disappeared. Some nuclear reactions occurred within minutes of the Big Bang, and almost all of the helium in the universe was synthesized at that time. As the expansion progresses, the universe gradually cools, just as hot air expands and cools. Cosmic background radiation is a relic of this early age. It has been properly termed the residual radiation of the original fireball. According to a scheme of universe evolution, as matter in the universe cools, it will eventually condense into a proto-galaxy. The proto-galaxy split into stars and gathered together into a vast and vast group. With the birth and death of the first generations of stars, heavy elements such as carbon, oxygen, silicon, and iron were gradually synthesized. When stars evolve into red giants, they throw out matter that condenses into dust particles. A new generation of stars has formed from clouds of gas and dust. In at least one such nebula, the cold dust collapsed into a thin disk surrounding the star. The dust particles attach to each other and accumulate into larger objects. These objects grow under the attraction of each other's gravity, forming a variety of celestial bodies from asteroids to large planets, which constitute the solar system.

The Big Bang theory guides us to trace the evolution of the entire universe, from the first few milliseconds of time to the formation of the earth and the emergence of life, and then to a potentially infinite future.