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Have you ever imagined how empty the universe is? The universe is an extremely mysterious space for humans. The earth we live on is located in the universe, and we are also living creatures in the universe.
But the universe seems to be an unknown space with neither beginning nor end. All we can look up at is the endless black space. The universe has never told us its story, and we know nothing about it.
However, the vast starry sky has always attracted human beings to go there. Human beings have always maintained great curiosity about the universe. With the development of science and technology, it seems that the secrets of the universe are also being revealed one by one. So the truth about how empty the universe is may be beyond your imagination.
How was the universe born?
If we want to know how empty the universe is, we must first understand the history of the universe. In many Eastern and Western mythological stories, the universe is considered to be the creation of God. In the West, people believe that God created everything, and the universe is naturally God's work.
In the East, we think that the Emperor of Heaven created everything in the world. However, from the perspective of modern technology and theory, scientists believe that the universe was probably born in a "big bang". This is currently the most famous " Big Bang " theory in the astronomy community.
As early as 1905, Einstein proposed the special theory of relativity, which caused a great sensation in the entire physics community at that time. In 1915, Einstein expanded the general theory of relativity on the basis of the original theory.
In the general theory of relativity, Einstein proposed a famous equation: The gravity field equation. The emergence of the equation provides a certain theoretical basis for the subsequent Big Bang theory of the universe.
Einstein discovered through this equation that the universe seems to be changing over time. This change may be shrinking inward or expanding outward. In short, it is different from the static universe view originally conceived by Einstein.
Later, in order to solve this problem, Einstein added the "cosmological constant" to it. As long as the constants can take reasonable values, it can also predict that the universe will not change with time.
But at that time, a physicist named Lemaître discovered clues from Einstein’s formula. He believed that the universe in Einstein’s eyes was unstable.
So on this basis, Lemaître proposed the "cosmic egg hypothesis", which believed that the earliest universe was actually formed from the continuous expansion of a " cosmic egg " that was about the same size as an atom. So the "Cosmic Egg Hypothesis" is also called the primary theory of the Big Bang.
Later, under the observation of astronomer Hubble , seemed to find evidence that the universe is undergoing dynamic changes.
In Hubble's observations, he found that galaxies outside the Milky Way seem to be constantly moving away from us, and the speed of distance is getting faster and faster. This also shows that our universe is actually in constant expansion.
This phenomenon happens to confirm Lemaître’s “Cosmic Egg Hypothesis”. Our universe is indeed growing in size.
In the subsequent further research, a scientist named Gamov, combined with quantum mechanics and other physical laws, conducted a more in-depth study of the dynamic changes of the universe. finally came up with the "nuclear fireball model", which was the earliest predecessor of the Big Bang.
Because scientists believe that the Big Bang will definitely leave residual heat, this residual temperature is also called: Cosmic Microwave Background Radiation.
At the same time, scientists also believe that after the Big Bang, the mass ratio of hydrogen element and helium element in the universe will show a trend of 3:1. Therefore, this cosmic microwave background and the abundance of helium elements are also considered to be the key to the establishment of the Big Bang theory.
How empty is the universe?
According to the current mainstream view, scientists infer from the cosmic microwave background radiation that our universe has been expanding for 13.82 billion years, and during this process, the diameter of the universe has reached 92 billion light-years, or even this value can be larger.
But these values are still theories after all, and according to research, the universe is actually still "growing". The specific size of the universe is likely to far exceed our imagination.
Because the space of the universe is so large, the distances between stars in the universe are actually very far away from each other. Although people often say that there are more stars in the universe than all the sand on the earth combined, the universe is actually still "barren".
Take the Milky Way that we are most familiar with as an example. The distribution of stars in the Milky Way is actually very uneven. The farther a star is from the center of the Milky Way, the lower the density of stars in that area. For every 326 light-years further away from the center of the Milky Way, the density of stars decreases by 2.9 stars per cubic light-year.
In our solar system, the density of our stars has dropped to 0.004 stars per cubic light-year. Calculated according to the average value, the average density of stars in the Milky Way is approximately 0.006 stars per cubic light-year.
According to this value, In the Milky Way, there is only one star every 167 cubic light years. The distance between stars is actually very wide.
Moreover, there are still cosmic voids in the universe, and many places are completely devoid of stars. Looking at it this way, the universe is actually much more empty than we imagined
Conclusion: Conjectures about the future of the universe
The universe is actually still expanding, and the distance between stars will only get farther and farther.
But for humans, the expansion of the universe is a long process for us. As a small part of the universe, human beings need to wait longer if they want to explore more secrets of the universe. We also need time to verify our conjectures about the universe.
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