When you look up at the starry sky and look at the starry sky and the boundless universe[1], have you ever thought about how the universe we live in was born, whether space has boundaries, and whether time is always there, through this article will take you to do an in-depth understanding.
Based on Hubble's law and the theory of the expansion of the universe [2], the cosmic microwave background radiation [3], and the abundance of elements in the universe [4], scientists speculate that the universe was born in the big **. Before the big **, the universe was a small ball of matter with infinite density and intensity, which we called the singularity.
The singularity is the starting point of the origin and evolution of the universe, and is also considered the starting point of time and space, the beginning of all matter and energy in the grand model. At the singularity, the universe has no time, the radius of the universe approaches zero, the curvature of space-time [5], heat, temperature, pressure, etc., all reach infinity, and the volume is infinitely small.
About 138200 million years ago, the singularity produced a large **, which continued to expand in a very short period of time. As the universe expands, the heat cools and the temperature drops, and energy begins to be converted into fine subatomic particles [6], which are the first substances in the universe into which energy is converted. Matter and antimatter[7] engaged in a fierce confrontation, and in the end matter won by a narrow margin. As the temperature continues to drop, the activity of the original ions slows down and begins to combine into the first atoms, first composed of hydrogen, then helium and lithium, a manufacturing process that lasted for 380,000 years, and after 380,000 years the universe cooled and electrons began to slow down and begin to combine with the newborn atoms.
About 200 million years after the Great **, hydrogen and helium atoms continued to coalesce to form nebulae under the influence of gravitational interactions [8], and then collapsed to form the first stars [9]. Stars are able to forge heavier elements through nuclear fusion [10] reactions, followed by supernova explosions [11]. Supernova explosions not only gave birth to elements heavier than iron, but also threw them into space, making a qualitative leap in the complexity of the universe and making chemical reactions possible. These changes formed the universe as we see it today.
Due to the presence of dark energy[12], the expansion of the universe is accelerating.
According to the conformal cyclic universe theory, the continuous expansion of the universe will eventually lead to all matter becoming diluted energy, and then there will be only ubiquitous black holes in the universe [13], when the cosmic microwave background temperature [14] drops to infinitely close to absolute zero [15], the temperature of these black holes will also be higher than the cosmic microwave background temperature at a certain time, and thus begin to release Hawking radiation to the cosmic microwave background [16], which will make the black hole smaller and smaller. Eventually, the black hole will be completely evaporated, and the universe will only be left with pure energy, turning back to the origin of the universe - the singularity, and the universe will start a new round of big **. Our universe is in this singularity-big-expansion-singularity that loops indefinitely. **10,000 Fans Incentive Plan
But when did this infinite loop of singularity begin, it's like an old philosophical question, is it the chicken that came first or the egg that came first?
Exegesis. 1] Universe: The corpse of the Warring States period (jiǎo) once said in his writings that the upper and lower four directions are called the universe, and the past and the present are called the universe. The universe does not depend on human consciousness and exists objectively. The universe is in constant motion and evolving. It is boundless in space and has no beginning and no end in time. The universe is a space-time continuum, the sum total of the physical world in which we exist, including all matter, energy, space, and time.
2] Hubble's Law and the Theory of Expansion of the Universe: In the early 20th century, astronomer Hubble and others discovered that galaxies in the universe are moving away from each other, and the farther away galaxies are, the faster they move away. This phenomenon is known as Hubble's Law and is direct evidence of the expansion of the universe. The expansion of the universe suggests that the universe must have had a starting point in the past, from which it began to expand to its present state.
3] Cosmic microwave background radiation: In the 60s of the 20th century, astronomers discovered cosmic microwave background radiation, which is the thermal radiation left over from the universe. The existence of cosmic microwave background radiation suggests that the universe was once in an extremely hot, dense state.
4] Abundance of elements in the universe: According to the grand theory, conditions at the beginning of the universe make it easier for light elements (such as hydrogen and helium) to form, while heavy elements are gradually produced during the subsequent stellar combustion. Astronomers have observed elemental abundances consistent with this theory**.
5] Curvature of space-time: A physical term that describes how the properties of space-time in a gravitational field are determined by the mass distribution of an object. Specifically, the distribution of the mass of an object can make the properties of space-time uneven, causing the curvature of space-time. Roughly speaking, the denser the matter, the greater the curvature of space-time. This also means that the curvature of space-time creates a gravitational pull. The object needs to follow the indication of curvature for motion. For example, the mass of the Sun determines the curvature of space-time in its vicinity, and the Earth orbits the Sun in an almost elliptical orbit due to this curvature.
6] Subatomic particles: Also known as subatomic particles, they refer to particles that are smaller in structure than atoms. All atoms are made up of smaller "subatomic" particles, including electrons, protons, and neutrons. Overall, subatomic particles may be electrons, neutrons, protons, mesons, quarks, gluons, photons, and many more.
7] Antimatter: Antimatter is the anti-state of normal matter, when the positive and antimatter meet, the two sides will annihilate each other and cancel each other, occurring ** and generating huge energy. It is made up of antiparticles, which are usually called electrons and protons, which have the same amount of electricity but opposite electricity.
8] Nebula: A nebula is one of the thin bodies made of gas or dust, containing almost all of the malleable objects except planets and comets. Their main component is hydrogen, followed by helium, and also contains a certain proportion of metallic and non-metallic elements. Nebulae provide a place for the birth of stars.
9] Stars: The formation of stars begins with a huge molecular cloud. These molecular clouds are mainly composed of atoms such as hydrogen, helium, and dust. In some areas, the gravitational pull gradually increases due to the increased density, which attracts more gas to accumulate towards it. When the mass of the gas gathered reaches a certain level, gravity compresses it into a spherical shape, forming the so-called "protostellar nebula".
In the interior of the protostellar nebula, hydrogen nuclei begin to collide with each other due to gravity and pressure, triggering nuclear fusion reactions. The energy produced by these reactions radiates outward through the layer of gas surrounding the star, maintaining the star's steady state. When the temperature and pressure of the star are high enough, the nuclear fusion reaction of hydrogen continues until the hydrogen is almost completely depleted.
10] Nuclear fusion: refers to the polymerization of atoms with small masses, mainly deuterium, under certain conditions (such as ultra-high temperature and high pressure) to form new nuclei with heavier masses (such as helium). Although the neutron is relatively large, because the neutron is not charged, it can also escape from the bondage of the atomic nucleus and be released during this collision, and the release of a large number of electrons and neutrons is a huge energy release.
11] Supernova Explosions: Supernova explosions usually occur only in very massive stars, which are usually 8 to 15 times the mass of the Sun or more. Before the explosion, the star could undergo millions of years of nuclear fusion, consuming most of the hydrogen fuel in its core. When hydrogen fuel is almost exhausted, the core of the star begins to contract and heat up, eventually triggering the nuclear fusion reaction of helium and other heavy elements. These reactions release a huge amount of energy, causing the outer layers of the star to be violently pushed into space, forming a supernova explosion.
12] Dark energy: Dark energy is an energy that drives the movement of the universe and acts as a repulsive force in the universe. Neither it nor dark matter absorbs, reflects, or radiates light. Dark energy is the conjecture of some people, referring to a kind of energy that fills space and has a negative pressure. According to the theory of relativity, this negative pressure resembles an anti-gravitational force over long distances. This conjecture is one of the most popular solutions to explain the accelerating expansion of the universe and the loss of matter in the universe.
13] Black hole: A black hole is a very special celestial body, with an extremely strong gravitational field, and even light cannot escape its attraction, so it is called a "black hole". It is formed during the evolution of stars, and when the star burns out the hydrogen inside the core and starts burning heavier elements, if the fuel inside the core is depleted, the star will lose energy support and the core will collapse. When the core collapses to a certain extent, the star's gravitational field becomes very strong, forming a black hole.
14] Cosmic microwave background temperature: refers to the blackbody temperature corresponding to the cosmic microwave background radiation (cmb), and its value is about 2725k。This temperature is the temperature of the electromagnetic radiation that pervades the entire universe after deducting all foreground radiation (including radiation from galaxies within the Milky Way and galaxies) in the entire sky, regardless of which direction it is measured. This radiation was produced 300,000 years after the Great **. The theory of the great universe believes that when the great universe occurs, the temperature of the universe is extremely high, and then it slowly cools down, and there is still about 3k residual thermal radiation.
15] Absolute Zero: is a theoretical limit temperature, representing the lowest possible value of temperature, about -27315 (or 0k). It is the zero point of the thermodynamic temperature scale, and according to the third law of thermodynamics, absolute zero is defined as the temperature at which the entropy of a thermodynamic system reaches its minimum in the ground state of its pure crystal. At absolute zero, the movement of molecules and atoms almost stops and no longer produces heat. When the temperature of a substance reaches absolute zero, it is considered to be completely heatless.
16] Hawking radiation: It is a kind of thermal radiation emitted by black holes, which is inferred from the theory of quantum effects. Because Hawking radiation can cause black holes to lose mass, when the black hole loses more mass than it gains, it shrinks and eventually disappears.