Earth is alive because it is in a "habitable zone" near the Sun. If the Earth is a little farther away from the Sun, it will become cold and cold; if it is too close to the Sun, it may become another Mercury or Venus. It is precisely because the earth is in a "just right" position that it can have the right temperature, so that liquid water can be retained, and eventually all life on the earth can be conceived.
But just as stars have habitable zones, do galaxies have habitable zones? Today we will unveil this bizarre question: Are there galactic habitable zones in the universe?
We use the term "habitable zone" to describe the regions of the universe that are more likely to conceive life. Typically, the term is often used to describe what is related to a planet and the distance between a planet and the star it orbits. Different stars have different habitable zones. The term "Goldilocks zone" comes from a children's story where a blonde girl with a barish personality called Goldenlocks (meaning "just right") breaks into the bears' house, eats their porridge and sleeps in their bed, and the little girl only likes everything that is just right, so she tastes all the porridge and lays down all the beds until she finds the one she thinks is the best.
In fact, not only do stars have habitable zones, but there may also be habitable zones in galaxies. This is because a galaxy is not completely peaceful, and there are many dangerous areas in it, and these regions reduce the likelihood of life. Taking the center of the galaxy as an example, astronomers believe that the center of each host galaxy has a supermassive black hole, and that it is very dangerous to get close to this black hole.
Extramassive black holes emit vast amounts of gamma rays, X-rays, and cosmic rays that kill all but the simplest forms of life. Black holes are able to create a huge gravitational pull that draws stars and planetary orbits into them. For our solar system, if there is such a large mass nearby, Comet Oort Cloud will crash into Earth more frequently and could cause the destruction of The Earth.
The center of the galaxy is not the only danger zone, and the spiral arm at the outer edge of the galaxy is equally dangerous. Countless stars go round and round there, dying and being born between supernova explosions. Gravity here, like the center of a galaxy, is so destructive that we would face a catastrophe if the solar system were unfortunate enough to be caught up in one of its spiral arms.
The Sun rotates at exactly the right speed around the center point of the Milky Way's planetary swarm, so it doesn't pass through the planetary swarm. The roundness of the sun's orbit is also just right. If the path of motion were more elliptical , the Sun would intersect the spiral arms of galaxies at some point. Humans may not survive the radiation and gravitational challenges it brings.
The possibility of human habitability in the milky way represents the possibility of human survival. Within the Milky Way, the ideal region for life to survive is about 13,000 to 33,000 light-years from the galactic center. Humans are fortunate to be in the ideal location of 27,000 light-years. There may be other life forms outside this area, but they may be simple ones. Advanced, complex life is difficult to adapt to dangerous environments like simple life forms such as bacteria. If there is also a suitable planet in the universe and there are habitable areas around the planet, this will further limit the possibility of extraterrestrial life.
This is what people often call the "star circumference habitable zone". A planet that meets the conditions for ideal life must be located not only in the habitable zone of its surrounding stars, but also in the habitable zone of its galaxy—and this galaxy must also be in the habitable zone of the universe. According to Guillermo Gonzalez, an astronomer at the University of Washington, the milky way has only 5 percent of the stars in the habitable zone at most.
As a result, the Sun is thought to be one of the few stars in the Milky Way that can support life. If there were other galaxies in the universe with habitable stars and planets suitable for life, we might never encounter physical life. There are too many conditions for a planet fit for life to meet. The expectation that there will indeed be other extraterrestrial life in the vast universe may be our wishful thinking.
Then again, what supports the argument that there is indeed a habitable zone in the universe? Perhaps the concentration of "metal" can be proved. For astronomers, any element heavier than hydrogen and helium can be called a "metal." It is now known that older stars are unlikely to exist around Earth-type planets. This is because they formed a long time ago in a relatively young universe. At the time of such star formation, since supernovae did not form heavier elements, most of the main floating elements in the universe were hydrogen, helium, and lithium.
Once enough stars exist and explode, heavier metallic elements are created to spread throughout the universe, forming Earth-like planets. In fact, our sun itself is peculiar, containing unusually high concentrations of metals. Probably because it formed in another region of the Milky Way with higher metal concentrations, somehow ended up here. Some regions of the universe may have higher concentrations of metals than others, forming planets where life could inhabit. Compared to galaxies in regions with lower metal concentrations, galaxies in this region have a great advantage in the existence of life in any case.
How will the existence of life belt galaxies change our understanding of the universe? In this way, the ideal conditions for the existence of the earth become even more incredible. Religions may be able to use this to encourage people to believe in the God who governs creation. The uniqueness of our human beings can support the claim that God created human beings in His own image. If other different intelligent beings are discovered, this claim will become more difficult to maintain. In addition to this, there may even be the optimal point in time for life to exist. There is an explosion known as a gamma-ray burst, one of the most powerful in the universe, so powerful that even if they occur somewhere far away in the Milky Way, they could destroy all life on Earth.
Powerful gamma-ray bursts could even destroy an entire galaxy! Such explosions were more common in the early universe, which lacked the heavy metals that formed the planets. These gamma-ray bursts are thought to erupt every billion years in our galaxy. If this is the case, we live in the belt of life in the dimensions of space and time. It is also possible that cosmic events are more likely to occur in certain regions of the universe, making it possible to assume that such a belt of life exists, in which galaxies are more likely to avoid such destruction. This is why the life belt may exist. What do you think? Is there anything we overlook?
by：两蚊，XM，RZ