Even with the use of advanced science and technology, there are areas in the universe that humanity can never reach. If there is a limit to which humanity can reach the universe, how big is the universe and how far away is it?
Looking at the night sky, it seems that there are infinite stars in the universe, but in reality, the number of stars is limited and stars also die. The diameter of the galaxy in which the Earth exists is up to 200,000 light years, and there are 100 to 400 billion stars between them. It’s just a vast galaxy, but I would like to know how many stars are born in a year, but they say there are only three. Again, it can be said that 95% of the stars in the universe already exist and humanity is living at the end of the universe. Therefore, the number of stars shining in the night sky will continue to decrease.
Not only that, but it’s also revealed that the universe is rapidly separating from humanity. There are not only galaxies in the universe, but also about 50 large and small galaxies, such as the Andromeda galaxy. The Milky Way belongs to the local group of galaxies.
Also, as a supercluster organizing several galaxies, there are countless superclusters in the universe. The local group of galaxies in which Earth exists is located within the Laniakea supercluster. There are currently about 2 trillion observable galaxies. Unfortunately, however, only 6% of the 2 trillion galaxies that humans can reach even if they travel at the speed of light. This means that 94% of observable galaxies already exist in unreachable regions. That there are many galaxies that humanity cannot reach.
Originally, the reason galaxies exist is related to the Big Bang. 10 years after the Big Bang-36At the beginning of time, the universe is a tiny bubble of energy. These energy bubbles are not completely uniform and some have a high density. In the process of cosmic inflation, energy of various sizes, from marble-sized energy to trillions of kilometers, rapidly expands in just a trillionth of a second.
During the rapid expansion, small differences in energy density are reflected in the distances between galaxies. Since the universe is composed of low-density regions, gravity is diffused and pushes the galaxies to move together, resulting in the formation of galaxy groups that organize different galaxies.
Meanwhile, the universe keeps expanding and cannot be stopped. Since galaxies in the universe are not constrained by gravity, the distance between galaxy groups decreases as the universe expands. To make matters worse, the expansion of the universe is accelerating. The reason is unknown and the concept of dark energy is created. The fact that the universe is expanding means that the universe has an end. However, since the universe is expanding faster than light, humans cannot observe the end of the universe. Thus, 94% of the universe that humans can observe is an unreachable area.
Why can humans observe stars that exist in unreachable areas? The reason is that humans see things through light. Light can travel through space at full speed, but it still takes time to travel. The light that reaches the Earth comes from all over the universe. Even though light is generated near the Milky Way, by the time the light reaches Earth, the light source may move to an area that cannot be reached from Earth. If we take into account the time taken for light to reach the earth, the light observed by man is from a long time ago, and it cannot be said that the stars and galaxies that emitted light are still in the same position.
In other words, the observable universe and the human-reachable universe are entirely different matters, and the observable universe is much larger. So, in a sense, the universe is showing us humans good things that are out of reach.
Humanity has no idea what the universe is like now because we are looking into the distant past of the universe. Furthermore, everything in the universe outside the local group of galaxies will someday fall beyond the observable area of humanity. In fact, up to 60,000 stars per second are disappearing beyond human observation. However, 60% of observable outer space still exists. This observable region covers a radius of 18 billion light years.
However, existing galaxies in this region still continue to move and are considered to have separated from the local group over time. Each group of galaxies is moving away at a speed of 5 million light years per second. The Maffei Group, the closest member of the Local Group of galaxies, also exists in a position that would take 11 million years to move at the speed of light from the Polar Group. Therefore, it is no exaggeration to say that a large group called the Local Group of galaxies is the largest range that humanity can reach. This is only 0.00000000001% of the entire universe.
As unknown forces such as dark energy continue to expand the universe, the distance between galaxies is getting farther apart, but at the same time, the number of existing stars in the area that humans can observe is said to increase in some cases . This is because our galaxy is predicted to collide with the Andromeda galaxy billions of years from now. If this collision occurs, it is said that there is a possibility that the star formation process will repeat itself for a while.
Also, if the universe keeps expanding, eventually all the galaxies in the observable area will disappear, and the only thing that exists in the universe is the merger of the Milky Way and Andromeda Galaxy.
The universe that humans can reach is 0.00000000001% of the total space, which is a small space every week, but it’s still so vast that mankind originally couldn’t even create the technology to move around this area without any inconvenience.
