One: The Universe Started with “the Big Bang”

Nowadays, any ordinary person knows that the sun we rely on to survive is just another ordinary star in the Milky Way, and that Earth is just another planet of the sun. Before the 1920s, however, the horizon of astronomers was confined to the Milky Way, as if the Milky Way was the entire galaxy. The first person to discover galaxies outside of the Milky Way was American astronomer Edwin Hubble. In 1925, he discovered the Andromeda Galaxy near the Milky Way through astronomical observation, marking the first extragalactic galaxy (i.e., a galaxy outside the Milky Way) observed by humans. In later observations, Hubble found that there were far more than one or two galaxies outside the Milky Way. Ten years after the discovery of the first extragalactic galaxy, the scope of astronomical observation expanded to a range of five hundred million light-years; that is the distance light travels (300,000 km per second) in five hundred million years. At the time, this observation distance seemed to be sufficiently large.

After observing numerous extragalactic galaxies, astronomers discovered that almost all of them were moving away from us, and the further those galaxies were, the faster they were moving away. For example, the Virgo Nebula is moving away from us at a rate of 1,000 kilometers per second; to the astronomers then, this was simply incredible. Why are these galaxies moving away from us? Where does our universe come from, and where is it heading? Many scientists have approached these questions from different perspectives. In 1927, Belgian astronomer Georges Lemaître suggested that all material of the universe could be traced back in time to an originating single point; he called this point the “Cosmic Egg.” When the Cosmic Egg suddenly exploded, the explosion material formed the stars. Today, the Big Bang theory of cosmic formation is accepted by most scientists, and this theory is being constantly perfected.

The universe was formed 13.8 billion years ago; of course, this is only a rough estimate. Different scientists have varied understanding of this number, but the differences are not significant.Therefore, it does not prevent our discussion. This time can be confirmed in at least three ways. The first method relies on the observation of galaxy retreat speed. If we rewind 13.8 billion years, the universe can be attributed to one originating point. The second mode focuses on the study of the universe’s oldest stars and the star clusters they form. Upon further inference, their ages are all close to 13.8 billion years. These are the first generation of stars formed in the universe. The third approach is centered around the decay of atoms; it uses the law of the atomic half-life to test the age of the oldest existing atoms.

The most common description humans use to describe cosmic origin states that the universe began with a primitive atom. This atom was much smaller than the atoms we refer to today; it had a diameter of only 10-33 centimeters, a high temperature, and large density. In specific numbers, this atom has a temperature of 1032 K and a density of 1093 grams per cubic centimeter. This primitive atom suddenly exploded 13.8 billion years ago. The space it created through that explosion is the universe; the debris it produced are the galaxies, stars, and various substances in the universe today.

However, the above description is not completely accurate. Our cosmology today is based on general relativity and quantum mechanics. Based on today’s scientific theory, we can trace the formation of the universe to 10-43 seconds after the Big Bang. This period is called the Planck time. The abovementioned figures are the cosmic scale, temperature, and density at this time. Using this state of time as the origin of the universe is actually very arbitrary; since there had to have been a “zero-point” and a singularity point before this time, we are merely unable to describe the universe before Planck time with existing cosmic theory.

It is not easy to truly understand the description of the universe. It first demands that we surrender our observation of the things around us and adopt a completely different way of understanding everything in which we exist and perceive constantly.

From a geometric point of view, a point is zero-dimensional, a line is one dimensional, a surface is two-dimensional, and a cube is three-dimensional. This is something we learn in junior high. We can easily imagine the shape of a point, a line, a surface, or a cube. But space is four-dimensional; we can perceive it, but we cannot imagine what it looks like. Of course, there will be many people who do not agree with this argument. They might ask: Hasn’t time always flowed naturally? Isn’t the universe the area we see? People have these doubts because they are confused by their personal experiences. According to existing understandings of cosmic theory, time and space came into existence at the moment of the Big Bang 13.8 billion years ago, and so time has flowed until the present and the universe has been constantly expanding to this day. Surely someone will ask: Even if there was no matter or life before the Big Bang, there must have been time . . . right? The answer is no. Time started with the Big Bang; there was no time before that. If the Big Bang created the galaxies and matter, surely there was empty space before the Big Bang—how else did the debris from the Big Bang disperse? The answer is once again no. Space came into being at the moment of the Big Bang; the volume of space is determined by the volume of the universe’s expansion. Someone might ask again: What is outside of the universe? What connects to the edges of the universe? The answer is that the universe only has size; it has no edge and does not touch anything. (There are scientists who believe that there are other universes outside of our universe, but we cannot see them since space is four-dimensional.)

When we observe the galaxy through a telescope, we discover that the further away a galaxy is, the faster it is moving away from us—that is not to say that we are the center of the universe. As a matter of fact, we would reach the same conclusion observing the universe from any planet in any galaxy. Just as when we blow balloons we might observe on any point on the balloon that the further away a point is the faster it is moving away. Observations made on any fixed point give the illusion that the observer is at the center. In reality, every point is just an ordinary point.

The explosion 13.8 billion years created the epoch. At the beginning of the Big Bang, the four natural forces we know today (strong interaction, weak interaction, electromagnetism, and gravitation) were unified. As the universe began to cool and expand, these four forces started to separate. At the same time, the asymmetry between matter and antimatter began to appear; matter outweighed antimatter by a tiny portion. These were the “Dark Ages” of the universe; in this dark space, particles and antiparticles annihilated into photons, producing energy. This annihilation included neutron-antineutron annihilation, proton-antiproton annihilation, electron-positron annihilation, and neutrino-antineutrino annihilation. Today, light fills the entire universe mainly as a product of the early Big Bang period, while the matter that remains from this large annihilation is our cosmic galaxy.

Three minutes after the Big Bang, the temperature of the universe fell to one billion K. During this time, protons and neutrons combined to form nuclei; this process lasted about an hour. When the universe’s temperature dropped to one hundred million K, the nuclear synthesis ended. According to theoretical calculations, among the products of the nuclear synthesis, hydrogen accounts for ¾, helium takes up ¼, while tiny amounts of lithium, beryllium, and boron account for less than one millionth of the whole. These theoretical figures have received initial confirmation through astronomical observations today.

During this time, the universe was full of photons, but it was not transparent due to the large number of free electrons also existing in the universe. These electrons blocked the path of photons. About thirty million years later, the temperature of the universe had dropped to 3,000 K, electron movement was less intense, and it was possible for hydrogen nuclei to capture one electron and turn into hydrogen atoms, for helium nuclei to capture two electrons and form helium atoms, and for lithium nuclei, beryllium nuclei, and boron nuclei to all capture corresponding electrons and form atoms. Without the electrons blocking their paths, photons were liberated and lit up the universe, ending the Dark Age. Concurrently, the universe moved from a radiation-based era to a matter-based era.

In the 1960s, while debugging the radio astronomical telescope, two engineers at the Bell Labs—Arno Penzias and Robert Woodrow Wilson— discovered that a very “cold light” occupied the universe sky. This “light” encompassed every star and every galaxy, filling every corner of the universe. It was not visible with optical telescopes but could only be observed through radio telescopes; its corresponding temperature was 3 K. We know that 0 K is absolute zero, measuring -273 C. This is the theoretical minimum temperature, and 3 K is exactly the theoretical calculation of the temperature of waste heat produced by the Big Bang. That cold light that filled the universe is the original light remnant of the Big Bang; it is the remains of the photons from the Dark Age of the universe. Since 13.8 billion years have passed and the universe has undergone a great expansion, the initial photons are now scattered throughout the universe and have become very sparse. Only a few hundred photons exist in every cubic centimeter, which equates to 3 K in temperature. Evenly spread across the entire universe, this light is called “Cosmic Microwave Background Radiation.” These two engineers’ accidental discovery proved to be the most powerful proof for the Big Bang Theory, and the two were awarded the Nobel Prize in Physics in 1978 for that reason.

At the same time the universe was expanding from the massive force of the Big Bang, atoms were being brought together by gravitational force to form huge clouds. Two hundred million years after the Big Bang, these atom clouds had finally been compressed tightly enough so that stars could be born. At this time, the universal temperature—that is, background radiation— had dropped to 30 K. The universe’s sky had changed from the earlier yellow and red to the darkness we see today, with dots of stars twinkling in the distance. Galaxies began to form as well; 13.8 billion years after the Big Bang, the universe is still continuing its outward expansion.


Two: The Universe and the Milky Way

There is no question that the Milky Way is also a product of the Big Bang, yet unlike the cosmic Big Bang theory, there is no consistent view regarding the formation of the Milky Way. The general belief is that a large cloud of atomic gas gathered due to gravitational force and formed a relatively enclosed and independent space shortly after the universe was created. Under gravitational force, a number of smaller enclosed and independent air masses formed within this large enclosed air mass; these smaller air masses became more and more dense, and their internal temperatures rose higher and higher. About two hundred million years after the universe formed, they ignited their own hydrogen nuclei one by one, producing enough heat to set the air masses aflame and form the first generation of stars. That original gas cloud encompassing hundreds of millions of stars evolved into one giant galaxy: the Milky Way.

According to research today, the Milky Way is a barred spiral galaxy comprised of a large number of stars. Some people compare it to the discs athletes throw, since it is also round, thin, and convex in the center. Along the diameter of this “disk,” we call the center the Galactic Center, and the convex part surrounding the center the Galactic Bulge, with the galactic disk and halo ranging around it.  

The Galactic Center of the Milky Way is flat and spherical in shape, measuring 16,000 light-years in diameter and about 13,000 light-years in thickness. It is densely populated by stars and is filled with dense interstellar matter and nebula. According to observation, there is a supermassive black hole in the nucleus area, supported by the existence of strong cosmic ray radiation, which is evidence of black hole phagocytosis.

The area around the center is semi-densely populated by stars and called the galactic disk; it measures 100,000 light-years in diameter, with a thickness of about 3,000–6,000 light-years. It is thicker near the center and thinner around the edge. The spherical shape surrounding the galactic disk is called the halo; it is about 100,000 light-years in diameter and is sparsely populated with stars, most of which are older and mineral-weak. Within the halo, some stars have aged to the last period of their star-life, and some of the larger ones even scatter their heavier elements through supernova explosion. These scattered elements land on the disk and become the “material” that form new star systems.

The galactic disk has a spiral arm structure that extends from the inside out, approximately symmetrical to the Galactic Center. The spiral arm contains more young, bright, metal-rich stars with denser galaxy dust, and it is also where stars are born. The Milky Way galactic disk has four spiral arms: the Norma and Cygnus arm, the Sagittarius arm, the Scutum-Crux arm, and the Perseus arm. At present, our solar system is located in the Orion arm, which is a minor spiral arm. The sun is 27,000 light-years away from the Galactic Center and slants about twenty-six light-years north off the surface plate; it revolves around the Galactic Center at a rate of 220 kilometers per second. Even at such high speed, one full rotation around the Galactic Center takes approximately 250 million years; thus, we call 250 million years one galactic year.

When we observe the sky with the naked eye, we cannot see the spiral nebula of the Milky Way, nor the spiral arm structures. In a clear summer night sky, all we can see is a bright river of stars stretched across the sky. This is because we are situated in the galactic disk and can only observe a side view of the Milky Way, so it will always look ribbon-shaped to us. There is a brighter, denser area near Sagittarius—that is the nucleus of the Milky Way.  

In gross estimation, there are about two hundred billion stars in the Milky Way (some scientists believe the number to be much higher—as much as two thousand billion galaxies) and around 300 billion galaxies in the universe. This is an extremely vast number. With so many stars and galaxies out there, it is humanly impossible to count them one by one. Even if every single person in the world spent their life counting, it would not be enough to tally all the stars in the universe. In fact, the number of stars and galaxies is obtained through “weighing.” It is calculated according to the orbit patterns of stars and galaxies.

Our galaxy is a relatively large galaxy within the universe, and it is not alone—there are about ten smaller galaxies surrounding it. Each of these galaxies has stars ranging in number from billions to tens of billions; there are even some dwarf galaxies with only a few million to hundreds of millions of stars. The Milky Way rules these galaxies through its gravity and dictates their movement. There are also bigger galaxies neighboring the Milky Way. In this lineup, the Milky Way can only claim second, with the Andromeda Galaxy reigning supreme. The Andromeda consists of nearly one hundred billion stars, and it rules more than ten smaller galaxies as well. In addition, there are some galaxies smaller than the Milky Way and Andromeda that are not governed by the two, but rather connected internally to form an independent, giant celestial system. We call this celestial system a “galaxy cluster,” or “galaxy group.”

The independent celestial system in which the Milky Way is located is relatively small, with only thirty galaxies. It does not quite reach the quota for a cluster—only a group. We call it the Local Group. Other galaxy groups near the Local Group include the Sculptor Group, the M81 Group, and the Virgo Cluster.

Galaxy groups (clusters) are all individually independent within the universe. As we know, galaxies are all moving away from each other, but that is not the case for the members in the Local Group. Apart from the ten or so satellite galaxies orbiting the Milky Way, the Andromeda galaxy, two hundred light-years away, is speeding towards us at a rate of 120 kilometers per second. According to this calculation, it will meet with the Milky Way in thirty billion years.  

In our universe, galaxy groups (clusters) are not the real giants; superclusters are celestial systems even larger than galaxy groups (clusters), and they take the throne. Superclusters are also known as second-order clusters and are comprised of smaller galaxy clusters or galaxy groups. The Local Group Galaxy Cluster is part of the Local Supercluster, which encompasses the Sculptor Group, the M81 Group, and the Virgo Cluster. The Local Supercluster contains about fifty galaxy clusters and galaxy groups, totaling thousands of galaxies. It is a flat, giant cluster of galaxy clusters with the Local Group located along its edge. The center of the Local Supercluster lies in the Virgo Cluster, sixty million light-years away. The Milky Way revolves around the center of the Virgo Cluster, completing one orbit about every one hundred billion years.

The two superclusters relatively close to us are the Perseus-Pisces Supercluster, twenty-five million light-years away, and the Hercules Supercluster, five hundred million years away. There is vast empty space between superclusters. In that distance of hundreds of millions of light-years, even the existence of interstellar material is extremely rare, not to mention celestial bodies.

The celestial system one level higher than superclusters is the cosmic universe we can observe today, called the metagalaxy. Because humans are still limited in terms of observation, the universe we can observe today is still far from the entirety of the universe.

In March 2016, the Hubble telescope observed the most distant galaxy we have discovered to date—the GN-z11, also known as the infant galaxy—13.4 billion light-years away from Earth. This is a very exciting record, as it not only conveys a far-off distance, but also a very distant time. As light travels, it not only produces distance, but it also brings information from the past; 13.4 billion light-years is not only the distance between two galaxies, but also the ancient information that a distant galaxy sends us. In other words, the infant galaxy we see today is not its current form, but a galaxy from 13.4 billion years ago. The infant galaxy existing now has far surpassed our current observations. It is important to note that the theoretical history of the universe is 13.8 billion years, which means that we can now observe any galaxy born four hundred million years after the creation of the universe.  

Is it also possible to gain an ultimate panoramic view of the entire universe as we continue to improve our observation techniques? It is theoretically impossible to achieve this ultimate goal. Hubble’s law tells us that the farther away a galaxy is from us, the faster it is moving away from us, since light has the fastest speed in nature. The farthest galaxies we observe today are already speeding away from us at a rate close to the speed of light, and farther-off galaxies are speeding away even faster. On one hand, they are moving away from us at a speed close to that of light, while on the other hand their light travels to us at the speed of light; these two opposing speeds offset each other. Just as we cannot produce actual distance on a treadmill, so the farthest corners of the universe can never be exhausted.

Now that we understand the macro structure of the universe, let us go back to comprehend its microstructure. We are in the stellar period of the universe’s history. According to theoretical calculations, this period should continue for hundreds of billions of years. The main players of the stellar period are naturally stars, and the sun we rely on for survival is one such star. When we peer into the night sky at the sparkling stars, we actually see stars burning in the distance. We can see a limited number of stars with the naked eye—only about 6,000 or so. The actual number of stars is trillions of times more than what we see. Many stars have already died and become white dwarfs, neutron stars, or black holes; they can no longer burn.

Stars are not static. Just as the sun orbits around the Galactic Center, other planets orbit according to certain rules as well. Stars do not exist in isolation either; they have many members in their families. First there are the planets that are gravitationally attracted to the stars—our Earth is one such ordinary planet in the solar system. Celestial bodies that orbit planets are called satellites. Satellites are also members of the stellar family, but they are controlled by the gravitational force of planets. The moon is the earth’s satellite. Satellites are not the smallest celestial bodies in the stellar system; in addition to satellites, there are many asteroids, comets, meteorites, and interstellar media that also react to the star’s gravity. All of these are members of the stellar family.

The space between stars is not necessarily a vacuum either. Interstellar gas and dust, cosmic rays, particle flow, and interstellar magnetic fields all exist in that in-between; they are collectively referred to as “interstellar material.” Interstellar material is extremely thin and unevenly distributed. During astronomical observation, concentrated cloud-like objects, called nebula, are often found in space. These are areas where interstellar material is more concentrated.

Stars are not evenly distributed in the galaxy. They tend to group in denser concentration towards the center of the galaxy and in sparser concentration along the edge. In the Milky Way, the nucleus is densely populated with stars, while the halo is more sparsely populated. This rule does not only apply to spiral galaxies like the Milky Way but holds true in elliptical galaxies, disk galaxies, and irregular galaxies as well. Apart from the distribution patterns mentioned above, some stars also form stellar cluster under the influence of gravity. These clusters have tens of thousands to tens of millions of stars, forming smaller stellar systems of their own. Stellar clusters can be divided into globular clusters and open clusters; they are all members of the galaxy and belong to the stellar family.

In the universe, dark matter and dark energy far outweigh visible matter. It is speculated that visible matter makes up only 5 percent of the universe’s matter, with the vast majority being dark matter and dark energy. With the current levels of science and technology, we know little about dark matter and dark energy, but we can determine their existence. If the actual rotational speed of a rotating galaxy is faster than its theoretical speed, we can deduce that there is non-visible matter accelerating its rotation. Likewise, if the expansion of the universe exceeds its theoretical speed, that means dark energy is playing a role.

Three: The Solar System and Earth

To understand the solar system and the earth, we must first start with their formation. In the Milky Way and in other corners of the cosmos, new stars form constantly. This phenomenon has been confirmed through astronomical observation, and the formation of the solar system can also be inferred from the formation of other stars.

The general belief is that the solar system was a gray cloud cluster before its formation, made up of countless air masses and dust particles. Most people believe that this cloud was a remnant of an exploding star that was tens of times larger than the sun. After the initial explosion, the debris was extremely hot, and it did not start to cool or darken in color until many years later. Due to the inherent gravity of the material, these substances slowly gathered together and became concentrated, with the central part becoming especially condensed. Through the role of gravity, the central area rose in temperature and density, indicating the birth of a new star; such birth processes were commonplace in the universe.

As the center of this air mass became increasingly dense, its core temperature reached ten million degrees. Volatile hydrogen nuclei finally gathered enough momentum to break through the electromagnetic barrier and collide, thereby creating nuclear fusions. The huge amounts of energy and light produced through nuclear fusion radiated out, creating a new star—that was the formation of our sun. Through analysis of the heavy elements in the solar system, we can deduce the sun to be a third- or fourth-generation star. As a star, the sun’s age is calculated from the moment of its nuclear fusion, dating back about five billion years.

As the sun formed as a star, the planets around it were also forming. Initially, there were many asteroids in the outer area of the solar system cloud cluster; the largest measured hundreds of kilometers in diameter while the smallest were only a few hundred meters in diameter. There were hundreds of millions of such small asteroids, and in addition, large amounts of rock fragments and ice existed as well.

Because these asteroids were so large in number, there was constant collision between them. Some such collisions produced comminuted explosions, resulting in numerous minute particles, while some smaller asteroids were absorbed by bigger ones during collision, causing them to grow in size. These collisions continued for many years until one day an asteroid gained enough mass to stand out from the group. The gravitational force of this bigger asteroid caused the surrounding asteroids to collide with it more frequently, making it more powerful at the same time. After many more years of collision, a planet was finally born. Our Earth was one such planet, born 4.6 billion years ago. Thereafter, the collisions lessened in frequency until finally tapering into calmness, and the earth entered a period of stability.

The solar system has eight planets, with Mercury being closest to the sun, and Venus, Earth, Jupiter, Saturn, Uranus, and Neptune following in order.

The moon is Earth’s satellite and is the astronomical body closest to Earth, with an average distance of 380,000 kilometers. Within the solar system, apart from Mercury and Venus, the other six planets all have their own satellites. Jupiter has the most, with sixty-nine confirmed satellites, while Saturn ranks second with sixty-two confirmed satellites. In addition to the eight planets and their respective satellites, dwarf planets, asteroids, and comets also exist in the solar system. Meteorites and interplanetary medium are also essential members of the solar system family.

As the absolute leader of the family, the sun’s mass accounts for 99.85 percent of the total mass of the solar system. The total mass of all eight other planets account for less than 0.135 percent. The planets’ satellites, comets, asteroids, meteorites, and interplanetary medium only account for 0.015 percent of the solar system.

Current scientific capabilities are enough to prove that the earth is the only planet with intelligent life in the solar system. No other planet has the environmental conditions to nurture and support intelligent life. After further studying the conditions required to produce intelligent life, one conclusion is certain: the true miracle of the solar system is the emergence of human beings. Even the formation of the sun pales in comparison, as there are countless stars in the universe, but very few star systems capable of producing intelligent life.


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