1. The size and age
of the universe What we usually call the universe refers to the objective universe, that is, the farthest (earliest) range of light energy reaching the earth. Beyond this range, because of the expansion of the universe, the expansion speed has already exceeded the speed of light, so that part of the "universe" can no longer be detected. This universe, which started from the big bang, will eventually be attributed to heat death (the ultimate increase in entropy, and everything will return to calm). Currently, as far as we know, it has a radius of 46 billion light-years and a diameter of 92 billion. (The specific value is about 28 × 109 parsecs (91 × 109 light years). Among them, its age is already 13.798±0.37 billion years.
2. The composition of the universe The
universe is almost composed of dark energy, dark matter and original matter. The other components are electromagnetic waves (about 0.005-0.01%) and antimatter.
Does it sound interesting? The more interesting ones are in the back. The
original matter includes atoms, stars, galaxies and life, and only occupies all the components in the universe. 4.9% (that is, everything we know, you, me, your beloved parents, the surrounding flowers and plants, nature, and stars, all of them, account for less than 5% of the total mass of the universe!).
Dark matter It is a mysterious form of matter that has not yet been detected, accounting for 26.8% of the total composition of the universe. Dark energy is the energy in the vacuum, which is also the cause of the accelerated expansion of the universe, accounting for 68.3% of the total composition of the universe.
However, right We currently know almost nothing about the nature of dark matter and dark energy, the largest constituents of the universe.
Matter, dark matter, and dark energy are evenly distributed over a large scale of 300 million light-years across the universe. On small scales, however, matter tends to aggregate into clumpy layers; most atoms aggregate into stars, most stars aggregate into galaxies, and most galaxies aggregate into clusters and superclusters, and finally into large scales fibrous structure. The observable universe contains about 300 streams (3×10^23) stars and more than 100 billion (10^11) galaxies. Typically galaxies can be as small as 10 million stars (10^7 dwarf galaxies), or as large as 1 trillion (10^12) stars, forming huge galaxies. The Milky Way is one of the galaxies in the Local Group of galaxies, and its supercluster is the Laniakea supercluster (the Virgo supercluster also belongs to this supercluster). The supercluster is 500 million light-years wide, while the Local Group is over 10 million light-years. The universe, by contrast, has vast voids; the largest known voids are 18 billion light-years across.
It is also worth mentioning that no matter where the universe is observed at any lookout point, it is uniform and isotropic, and the universe has no so-called center.
Come, come, look at the picture~
The Spatial Scale of the Objective Universe
3. The origin and end of the universe The
universe originated from a big bang, which is a relatively recognized statement in the mainstream scientific community in recent years.
Big bang, big bang, sounds so cool~
Many people want to ask, what was before the big bang, and what was outside the big bang?
I'm going to be rude to say, nothing before, nothing outside?
What's the meaning?
At the moment of the big bang, it is not matter that expands, but space and time!
Wow, what does that mean, before the big bang, there was no such thing as time! What we call inside and outside is the concept in space, and after the big bang, space was created, and everything was created in this space, there is no concept of "inside and outside"!
Cool or not~
big bang model
Now that we know how the universe was born, we also want to know how it "dies".
Regarding the end of the universe, scientists began to speculate that the gravitational force of matter would cause the expansion of the universe to slow down. Therefore, the ultimate fate of the universe is determined by the amount of matter: if the density of matter exceeds the critical density, the expansion of the universe will eventually stop and reverse to contraction, eventually forming a "big crunch" as opposed to the "big bang". ); if the density of matter is equal to or lower than the critical density, the universe will continue to expand. Density (fat and thin) not only determines the fate of human beings (especially girls), but also determines the life and death of the universe. It's amazing~
It is also worth mentioning that the geometry of the universe is also related to density: if the density is greater than the critical Density, the geometry of the universe should be closed; if the density is equal to the critical density, the geometry of the universe is flat; if the density of the universe is less than the critical density, the geometry of the universe is open. Also, the expansion of the universe is always slowing down.
However, according to astronomical observations of supernovae and cosmic microwave background radiation in recent years, although the density of matter is less than the critical density, the geometry of the universe is flat, that is, the total density of the universe should be equal to the critical density. And, expansion is accelerating. These phenomena suggest the existence of dark energy (dark energy! Cool name, but totally calculated and observed) in the universe. Unlike what is commonly called "matter", the gravity produced by dark energy is not a gravitational force but a repulsive force. In the presence of dark energy, the ultimate fate of the universe depends on the density and properties of dark energy. It is less likely to be a "big squeeze", it may be a gradual expansion to stabilize, and it is more likely to continue to expand infinitely or continue to accelerate. Even the "big rip" where atoms are destroyed. At present, due to the lack of understanding of the nature of dark energy, it is difficult to make positive predictions about the fate of the universe.
This is the information we know, and there are some other things that I would like to say, we need to know that the vastness of the universe is beyond our imagination, but it is our small and humble human beings living on the earth, you and I, When we look at the universe, the layers of veils are lifted, we are constantly approaching the truth, and the universe, the universe is like the coldest goddess, we can never fully appreciate her beauty until the last veil is lifted.
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