Looking to the end of the universe

　　When looking up at the stars, many people probably think: What is the end of the universe?
　　Maybe after not too long, you might know what it is.
　　At 8:15 p.m. Beijing time on December 25, 2021, at the Kourou Space Base in French Guiana, South America, the Ariane 5 carrier rocket successfully lifted off with the Webb Space Telescope. The most advanced telescope to date will reach the Lagrangian L2 point, which is 1.5 million kilometers away from Earth, within a month. After another 6 months of adjustment, it will be possible to see images 13.5 billion light-years away, close to Origin of the universe.
　　That could be the end of the universe.
　　Of course, this is all based on our current Big Bang theory, which is correct.
　　According to the Big Bang Theory, the universe we are currently living in and known to is 13.8 billion years ago, when a group of extremely high temperature, extremely high density, and extremely high pressure substances suddenly changed, and in a very short period of time Formed by rapid expansion and cooling. In just a few seconds, explosion-like expansion and cooling takes matter from elementary particle forms such as electrons, photons, and neutrinos, to atoms, nuclei, molecules, and composites into the usual gas. The gas gradually condensed into nebulae, which further formed into the various stars and galaxies that eventually formed the universe today.
　　The beginning of the universe was 13.8 billion years ago. If you want to explore the origin of the universe, you need to go back to the original time, 13.8 billion light-years away, where there is the original light of the Big Bang, which is theoretically the pole that we can perceive. It can be said that all human exploration of space and universe so far is to get as close as possible to there.
　　How to see it? The best way is to detect electromagnetic waves. Any object above the absolute temperature of zero will release electromagnetic waves. The higher the temperature, the higher the frequency and the shorter the wavelength of the electromagnetic waves released. Most electromagnetic waves are black body radiation, which cannot be seen by the naked eye. Only electromagnetic radiation with a frequency of 385-750 terahertz and a wavelength of 780-400 nanometers can be seen by us, that is, visible light that is divided into seven colors in daily life. Using such principles, humans have created a range of detection and transmission devices, from invisible radar detection, radio wave transmission, to visible optical telescopes, microscopes, and more.
　　The same is true for perceiving the universe. We have radio telescopes and optical telescopes. In terms of human perception, optical displays are more intuitive and clearer. The optical display shows that in addition to the visible light of the seven-color spectrum, there is infrared light with a longer wavelength outside the red end, and ultraviolet light with a shorter wavelength outside the purple end. Although infrared and ultraviolet cannot be directly visible, they can be recorded and recorded by instruments. The display greatly enhances the human vision. For example, through infrared searchlights, you can see a clear scene in the dark night where you can’t reach your fingers.
　　Optical telescopes used for cosmic exploration, the most famous before is the Hubble telescope, which is mainly used for visible light and ultraviolet light detection. However, the dust caused by the movement of celestial bodies in the universe will absorb a large amount of visible light and block a large number of stars and planets. Therefore, the newly launched Webb telescope adopts infrared detection, hoping to penetrate the dust, perceive farther, and see the fainter objects in the deeper part of the universe. Heat sources and hidden secrets.
　　Hubble has a diameter of 2.4 meters, and Webb’s main mirror has a diameter of 6.5 meters and an area of ​​25.4 square meters, which is 6 times that of Hubble. 6.5 meters is more than the diameter of the Ariane rocket, so Weber’s lens is subdivided into 18 hexagonal mirrors, which are folded and opened in space. Because the lens will work in an environment below minus 220 degrees Celsius, it is made of alkaline earth metal beryllium, which has strong rigidity, high thermal stability and conductivity, and low density. The processing accuracy is controlled within 10 nanometers, only dozens of beryllium atoms. length. The surface is sprayed with a layer of 120 nanometer thick gold by vapor deposition to improve the conduction effect, that is, the sensitivity. A very thin layer of silicon dioxide is sprayed outside the gold layer to protect the soft gold layer.
　　At the Lagrangian L2 point, Weber and the Earth and the sun form a straight line and have the same gravitational force, and the relative position remains unchanged. However, sunlight will cause Weber to heat up, which is not conducive to infrared observation. For this reason, on the side facing away from the sun, a 300-square-meter area of ​​five layers of solar shields are set up to protect the sun’s heat. Each layer is composed of a silicon film and an aluminum film formed by electroplating, and the thickness is between 25 microns and 50 microns. Each layer can reduce the heat by 90%, and is supplemented by liquid helium refrigeration technology, which can finally reduce the temperature by 300 degrees Celsius. Make sure the Webb telescope is always working around -230 degrees Celsius.
　　In January 2020, Hubble discovered a triplet group of galaxies EGS77, which was born about 680 million years after the Big Bang and is the most distant and oldest galaxy group ever discovered. According to predictions, the Webb telescope will be able to observe galaxies more than 13.5 billion years ago, when the Big Bang was only more than 200 million years away, very close to the origin of the universe, and it is very possible to observe the formation and evolution of the first celestial bodies in the universe.
　　Perhaps, that is the far end of the universe.