"To my surprise, we are not interested today in physics, space, the universe, the philosophy of existence, or the final destination discussion. It's a crazy world, and you have to keep a curiosity at all times. —Stephen Hawking
Every curious person has asked the question of the origins of existentialism: Where do we come from? We humans naturally like to trace the origins, and the most common phrase we say every day is "Why?" Curiosity about the unknown and an adventurous spirit of exploration are the potential driving forces for the progress of human society! So no matter what you're doing now, what kind of career you're pursuing, be passionate about life and always be curious!
Today we will review the entire history of the universe in just 10 sentences and answer the question "What caused our existence".
<h1>1, soaring</h1>
We generally think that the universe began at 10^-36 seconds, when the universe is composed of empty space-time and a large amount of inner energy, and is in a state of exponential expansion, that is, the cosmic inflation stage, which ends in 10^-33 seconds! So there will be a question, many people think that the universe began to expand from a point, there must be a center, the central region is not free of matter? In fact, no, you can imagine that the inflation of the universe starts from countless tiny regions, bubbling everywhere like boiling soup, and the quantum fluctuations will also be stretched to the entire universe with the surges everywhere, and these quantum fluctuations also create the "seeds" of all the structures in the future! That's what we think about the origin of the universe at the moment.
<h1>2. Reheat</h1>
About 13.8 billion years ago, a certain region of space-time contained our entire observable universe today. After the inflation ends, the vacuum energy in space-time is converted into matter, antimatter, and radiation. This period is known as the reheating phase of the universe. That is to say, inflation was the beginning of the Big Bang, because inflation created a dense, hot, material- and radiation-filled universe.
<h1>3. Antimatter disappears</h1>
As the universe expands and cools, the energy of the universe is not enough to continuously produce the pairs of matter and antimatter, and the positive and negative matter that existed before will be annihilated, but the universe seems to prefer matter, because the basic asymmetry between matter and antimatter has led to a weak advantage of one billionth of matter over antimatter. At present, this asymmetry is also the biggest unsolved mystery of cosmology, according to the particles that already exist in the Standard Model, it is not enough to explain why such an anomaly occurred, so we think that in the extreme environment of the early universe, there must have been high-energy particles that we have not yet discovered.
<h1>4. Neutral atoms</h1>
As the universe continues to cool and expand, excess matter is annihilated along with antimatter, leaving only a small amount of matter, while radiation is gradually transferred to lower energies, and protons and neutrons are combined to form stable nuclei, eventually forming neutral and stable atoms. This is the first nuclear fusion in the universe since the Big Bang! It contains a large number of hydrogen atoms (a single proton) and a small amount of helium, as well as extremely trace amounts of lithium.
<h1>5. Bright stars</h1>
As neutral atoms formed, the universe also began to become transparent, and from all directions emitted the first rays of light in its history, which we call microwave radiation. At this time, the composition of the universe is dominated by the density of matter, so the universe is dominated by matter, that is to say, at this time, matter can form a huge network structure under the action of gravitational collapse, and the first stars are ignited by gravity after 50 million to 75 million years.
<h1>6. Reionization</h1>
We know that thick neutral clouds are also opaque to visible light, because the wavelength of light absorbable by neutral hydrogen atoms falls in the visible light band. But as the first stars formed, their fiery radiation could re-ionize the central atoms, making the universe transparent to visible light, a phase we call the "cosmic reionization period," so we can now see light from distant galaxies. At this time, the universe also formed clusters of stars, galaxies, and galaxy clusters in layers, and tried to form superclusters at the largest scales.
<h1>7. Heavy elements</h1>
Over time, the most massive stars ran out of core fuel and died in a supernova explosion that triggered the formation of the next generation of stars, which alternated the lives and deaths of stars, enriching the surrounding interstellar medium with heavier and heavier elements.
<h1>8. Organic molecules</h1>
After generations of stars were born, existed, consumed fuel, and died, the interstellar medium contained enough complex chemical elements that all new stars and star systems that formed would contain large numbers of elements and organic molecules that were essential materials for life. According to the observations of astronomers now, organic molecules are not unique to Earth, and it is likely that they were not produced after the formation of The Earth, because we have found a large number of organic molecules in the active star-forming nebula! The new discovery also opened up a new field called astrochemistry.
The combination of cosmology and astrochemistry can explain the universality of life in the universe, so why are there so many organic molecules in the nebula after the death of stars, and under what mechanism are these organic molecules formed? You can search through the headline APP for "The elements in the universe come from stars, where did the large number of organic molecules come from?"
<h1>9. Solar System</h1>
About 9.2 billion years after the Big Bang, an inconspicuous small region 25,000 light-years from the center of the Milky Way formed a new cluster of about 1,000 stars, one of which was born at the center of a protoplanetary disk that collapsed into 8 planets, 4 of which were internal worlds made of rocks, and the other 4 were outer giant planets made up of gas.
<h1>10, you and me</h1>
Hundreds of millions of years later, complex life dominated by chemistry took off in the first three worlds of the solar system, and over billions of years, a variety of life forms evolved, eventually clumping together 10^28 atoms to form us.
That's why the universe came from nothing and created us in just 10 sentences! It may seem coherent, but not all of the ways in which events occur are fully understood.
<h1>Summary: There are still issues that we need to explore</h1>
Regarding the inflationary phase before the Big Bang, it is unclear how the universe entered a state of exponential expansion, whether this state has always existed in the past or ..... And it's not clear how the universe existed in the first place. This is indeed a big problem, and it is estimated that it is not a problem that we can solve casually!
Details of how the cosmic inflation ended (the "graceful exit" question) and how energy was transferred to matter, antimatter, and radiation (the "cosmic reheating" problem) have yet to be universally agreed upon. These are the questions we are more concerned about!
We do not yet know the exact mechanism of the asymmetry observed between matter and antimatter.
We don't know if life just originated in our own world, in another world? Or interstellar space; all we know so far is that life began to appear on Earth about 3 billion years ago. These are the problems we need to solve in the future.