Astronomers believe that the true diameter of the solar system is 2 light-years. Although planets and their satellites end near the Kuiper Belt, there is still something beyond it called the Oort Cloud. This Oort Cloud, with a diameter of 2 light-years, is mostly made up of comets and is composed of material left over from the formation of the solar system. Compared to the Oort Cloud, the entire solar system is like a nucleus compared to an atom. This situation is similar for other stellar systems as well, making emptiness the mainstream in the universe. 

In 1981, astronomer Robert Kirshner discovered the first cosmic void in human history using a radio telescope. It had a range of 330 million light-years and an almost star-less region inside. Because this void is located in the constellation of Bootes, it is also known as the Boötes Void. At that time, astronomers estimated that if the Milky Way was located at the center of this void, humans might have believed that the universe only consisted of the Milky Way galaxy. 

The diameter of the solar system is currently 2 light-years, together with 400 billion stars, they make up the Milky Way with a diameter of 180,000 light-years. The nearest galaxy to the Milky Way is the Andromeda Galaxy, located 2.54 million light-years away. Together with 50 other smaller galaxies, they form the Local Group, with a diameter of 10 million light-years. When several groups of this magnitude gather, they form galaxy clusters with a diameter between 100 million and 200 million light-years, containing at least 2,500 galaxy-sized star systems. However, compared to the Boötes Void with a diameter of 330 million light-years, these galaxy clusters are still much smaller. 

1000万光年的本星系群。

The largest celestial structure that surpasses the Boötes Void is the Laniakea Supercluster, with a diameter of 520 million light-years and containing 100,000 galaxies. In current computer simulations, the Laniakea Supercluster's shape is like a feather, and the Milky Way is just a small, bright spot on one of the branches. From a physical perspective, the existence of the Boötes Void should not be possible. The universe is fundamentally driven by gravity, so the gravitational law should evenly distribute star systems throughout the entire universe, rather than creating a void with a diameter of 330 million light-years. 

Astronomers believe that there must be other substances in the Boötes Void that we have not yet discovered. These mysterious substances block gravity and enable the existence of the void. They are dark matter and dark energy, which astronomers believe together make up 95% of the total energy in the universe, while the visible galaxies only make up 5%. Therefore, voids occupied by dark matter and dark energy must be universally present within the observable universe, but we have only discovered a small fraction of them so far.

Overall, both cosmic voids and the Laniakea Supercluster are superstructures in the universe, while the Milky Way, the solar system, and Earth are just tiny specks. Our current goal is to continue developing space technology to enable human civilization to become a space-faring civilization as soon as possible.