The imprint of the universe and the return of all things

The following content is popular science content. If the reader is not interested in this, you can skip this section.

(Note: The"Big Bang Cosmology" believes that 13.7 billion years ago, before the birth of the universe, there was a point with infinitely small volume, infinite density, infinitely high temperature, and infinite space-time curvature. This point is called"Singularity". Point". All known physical laws fail at the singularity. The universe was formed by the expansion after a big explosion at this singularity, and the universe is still expanding. The Hubble expansion observed at the current galaxy redshift , precise measurements of the cosmic microwave background radiation, and observational data such as the abundance of light elements in the universe all support the Big Bang theory and are important evidence to confirm the theory.

"Inflation theory is a patch on the Big Bang theory""The"inflation theory" believes that at the beginning of the birth of the universe, the space of the universe expanded exponentially. This rapid expansion process is called"inflation", that is, the universe grew at an astonishing rate in a very short period of time. Inflation. According to this theory, the inflation process occurred between 10^-36 seconds and 10^-32 seconds after the Big Bang. After the end of inflation, the universe continued to expand, but the expansion rate was much smaller.

Due to space explosion Inflation makes the universe very flat, the curvature of space is close to zero, and the temperature of the entire universe becomes uniform. The quantum fluctuations that occur during inflation cause subtle differences in the temperature of the universe, which provide the basis for the formation of stars and galaxies in the future universe. Create conditions. In addition, inflation can also reduce the number density of massive exotic particles, such as the magnetic monopoles predicted by many derivative theories of the standard model of particle physics. Therefore, the"inflation theory" can explain the"large There are three difficulties in"Explosion Cosmology": it is difficult to make space isotropic, it is difficult to find that the observable universe is flat, and it is difficult to disappear magnetic monopoles.

""Big Bang Cosmology" and"Inflation Theory" jointly describe the birth and formation process of the universe. According to these two theories, the birth and formation process of the universe has gone through several stages, which are: (

1) Planck time (10^-43 seconds after the Big Bang): The earliest period after the birth of the universe was a period of very high temperature, which was high enough to allow the four fundamental forces (gravity, electromagnetism, weak force, and strong force) to All are unified into one basic force - super force. All known physical and mathematical laws are invalid. There is no matter and radiation in the universe.

(2) The period of great unification (from 10^-43 seconds after the big bang to 10^-36 seconds): As the universe cools (although the temperature of the universe is still very high at this time), gravity begins to separate from the other forces (electromagnetism, weak force, strong force). During this period, matter and energy are free

(3) Inflation period (10^-36 seconds to 10^-32 seconds after the Big Bang): The size of the universe expanded by 10 to the 26th power, which is equivalent to the expansion of a grain of sand into the observable universe. Large. As the universe further cooled, the strong force began to separate from other forces (electromagnetic force, weak force). After the universe experienced a brief period of inflation, the energy inherent in the space itself was gradually converted into various positive and negative particles and radiation.

(4) Quark period (10^-32 seconds to 10^-12 seconds after the Big Bang): The universe becomes a pot of particle soup, and a large number of quark-antiquark particles emerge from energy and are annihilated into energy again. Gluons, Particles such as gravitons and Higgs bosons also appeared during this period.

(5) Particle period (10-12 seconds to 1 second after the Big Bang): The universe becomes cold enough and the electroweak interaction breaks down into electromagnetic interaction And the weak interaction, that is, the electromagnetic force and the weak force are separated from each other. All four basic forces appear. The forces and physical laws in the universe are the same as today. Quarks (antiquarks) gather under the strong interaction force Together, protons and neutrons (antiprotons and antineutrons) are born. Bosons, neutrinos, electrons, quarks, and gluons stabilize.

Subsequently, positive particles (protons, neutrons, etc.) and antiparticles ( Antiprotons, antineutrons, etc.) collide with each other and then annihilate. Since positive matter has a slight advantage compared with antimatter, the antimatter (antiparticles) are almost annihilated, while a small part of positive matter (positive particles) remains. And provided the origin for most of the matter that makes up our universe today.

(6) Nuclear Period (1 second to three minutes after the Big Bang): After the temperature of the universe continues to decrease, the nuclear force (strong force) has been able to bind protons and neutrons, Stable nuclei of hydrogen and helium are formed (nucleosynthesis). However, the energy of electrons is still too high to combine with the nucleus, so neutral atoms cannot yet be formed.

(7) Atomic period (300,000 years after the Big Bang): As the universe As the temperature drops further, protons and atomic nuclei begin to capture electrons, forming the original neutral atoms. The electrons are bound in the nucleus and can no longer scatter photons. Matter and radiation are then"decoupled". Photons begin to propagate in the universe in the form of radiation, The universe has since become transparent. The universe dominated by radiation has transformed into a universe dominated by matter.

(8) Stellar period (200 million to 3 billion years after the Big Bang): A large number of hydrogen atoms gather together under the influence of gravity. The more hydrogen atoms, the greater the mass and the greater the gravitational force, which in turn attracts more hydrogen atoms. Finally, at a certain moment, nuclear fusion of hydrogen occurred under the huge pressure brought by gravity, thus stars were born, and the universe was lit up. After the star is born, the surrounding material slowly gathers to form planets or satellites, which together form a star system. Later, many star systems converge to form a galaxy.

(9) Dark energy period (about 5 billion years ago): As the universe continues to expand, the density of dark matter and matter continues to decrease, and dark energy begins to replace dark matter and matter to occupy the dominant position in the universe. The expansion of space stopped slowing down and started accelerating instead. Neither dark matter nor dark energy absorbs, reflects, or radiates light, so humans cannot directly observe it using existing technologies. Dark matter produces gravitational force, while dark energy produces repulsive force. The larger the space of the universe, the more obvious the dark energy is, and the greater the repulsive force generated. This repulsive force drives the continued expansion of the universe.

Some knowledge about black holes: Black holes are a type of celestial body existing in the universe in the modern general theory of relativity. The gravity of a black hole is so strong that the curvature of space-time is so great that not even light can escape from its event horizon. According to Einstein's general theory of relativity, when a dying star collapses, it will collapse toward the center and eventually become a black hole, swallowing all light and any matter (including planets, satellites, and other celestial bodies) in the nearby universe.

Usually stars initially contain only hydrogen, and the hydrogen nuclei inside the star collide with each other all the time and fuse. Although the star is very massive, the energy generated by fusion can compete with the star's gravity and maintain the stability of the star's structure. When a star ages, its thermonuclear reactions have exhausted the fuel in the center, and there is not much energy produced by the center. In this way, it no longer has enough strength to bear the huge weight of the shell. Therefore, under the heavy pressure of the outer shell, the core begins to collapse, and matter will march unstoppably toward the center until it finally forms a star with an almost infinitely small volume and an almost infinite density. And once its radius shrinks to a certain extent, the distortion of space-time caused by its mass will prevent even light from being emitted outwards.——""Black hole" is born.

Hawking's black hole radiation theory believes that although a black hole is like a monster, it will continue to swallow the material around it, causing its own mass to continue to increase, and the increasing mass will cause the boundary (event horizon) to expand. This will cause it to swallow more matter, but the expansion and swallowing of black holes is not infinite. In fact, black holes will lose mass due to Hawking radiation, and eventually completely evaporate and die. The so-called

"Hawking radiation" is speculated based on the theory of quantum effects A kind of thermal radiation emitted by a black hole. According to the Heisenberg uncertainty theory of quantum mechanics, absolute vacuum does not exist, and the energy of the vacuum field cannot always be 0. Therefore, what we think of as vacuum is actually Pairs of virtual particles are constantly and randomly generated. The two virtual particles quickly disappear and annihilate after collision. This will neither violate quantum mechanics nor energy conservation. This phenomenon is called"quantum fluctuation".

When When vacuum quantum fluctuations are applied to extremely curved space-time, such as near the event horizon of a black hole, something magical happens. Randomly generated pairs of virtual particles may be separated far enough by the powerful tidal force of the black hole before they are annihilated. When they are separated by When the wavelength of the virtual particle is reached, the virtual particle will transform into a real particle. However, when two virtual particles transform into real particles at the same time, based on energy conservation, one of them will have positive energy and the other will have negative energy to ensure The total energy is always 0. The normal space-time outside the event horizon does not allow the existence of negative energy real particles. Therefore, the real particles produced outside the black hole event horizon must be positive energy real particles, and the real particles swallowed by the black hole into the event horizon must be negative energy. Yes. After the black hole swallows the negative energy particles, its mass decreases, and the positive energy real particles outside the event horizon escape the black hole in the form of radiation. This radiation is"Hawking radiation". Under such a mechanism, the black hole will Constantly"evaporating", the mass will become smaller and smaller, the temperature will become higher and higher, the radiation intensity will become greater and greater, and eventually it will be wiped out in a violent radiation burst. This is the end of the black hole.

The theory of no boundary conditions, It was the physicist Hawking who proposed a boundaryless cosmology that is both self-consistent and self-sufficient. This theory believes that the boundary condition of the universe is that it has no boundaries, and everything in the universe can in principle be predicted by physical laws alone. The universe itself is created out of nothing (in the quantum sense) or has no origin (in the classical sense). If the no-boundary condition is true, it means that the universe is self-sufficient, which means that the universe does not need a creator God or does not exist. A push.

Hawking uses Euclidean quantum gravity to describe the origin of the universe. In this model, the real time that we are familiar with and can perceive (real time) is replaced by a virtual time like the fourth dimension of space. Instead, according to Euclidean methodology, the virtual time universe history is a four-dimensional sphere like the surface of the earth (but it has two more dimensions than the surface of the earth). That is, Euclidean space-time is an endless closure like the surface of the earth. Curved surface. In this model, the singularity of the universe is equivalent to the South Pole of the Earth. Therefore, just as"there is nothing south of the South Pole of the Earth", there is nothing before the singularity of the universe..

Conformal cyclic cosmology was proposed by physicist Penrose. This theory holds that the universe does not have just one big bang, but cycles through"aeons" from the big bang to death. The so-called"eternity" (aeon) is the"life cycle" between the creation of the universe from the Big Bang to the next Big Bang. After the creation of the Big Bang, the universe will not expand forever. When all the black holes in the universe evaporate through"Hawking radiation", all the mass in the universe will decay into radiation (that is, all matter will be converted into energy). The state of the universe will look almost exactly like the state at the time of the Big Bang. Through a mathematical transformation called"conformal transformation", the infinite future of the universe can be connected to the infinitesimal Big Bang singularity. In this way, the universe continues to cycle from one"eternity" to the next"eternity".

Penrose believes that the universe has always followed the second law of thermodynamics - the law of entropy. Before the Big Bang at the singularity, the entropy of the universe was at its lowest. When the Big Bang occurred, the entropy value began to increase continuously. As entropy increases, the universe becomes increasingly unstable. When the entropy value of the universe reaches a maximum value and approaches infinity, celestial bodies begin to gradually destroy, and black holes continue to grow, swallowing up all matter and converting it into energy. The entropy value slowly decreases along with this process. In the end, the black hole evaporates, the entire universe becomes a space of pure energy, and the entropy is completely cleared. Then, the energy space collapsed to a singularity state, a new big bang occurred again, and the new universe began to expand and evolve.

Quantum creation theory (quantum creation) was proposed by cosmologist Vilenkin. This theory holds that the universe can be born automatically based on quantum mechanisms. In quantum theory, there is a certain principle that pairs of particles can spontaneously and briefly emerge from empty space (the phenomenon of"quantum fluctuation"). Based on this phenomenon of vacuum quantum fluctuations, Wilenkin proposed a quantum mechanism that can produce an expanding universe from a state with no time, no space, and no matter. (The principle of this mechanism is to use quantum rules to create a micro-bubble space with momentum in the void, and the momentum will cause it to expand to the scale of the universe.) Therefore, Velenkin believes that before the singularity big bang, there was nothingness, and the universe It is produced from nothingness by quantum fluctuations. )

Feilu’s 18th anniversary brand upgrade gives back to readers! Recharge 100 and get 500 VIP points!

Grab a deposit now (activity time: August 10th to August 20th)