The earth is no longer perfect? Scientists have found that 24 planets are more suitable for human habitation than the earth.

The existence of life has certain requirements for the environment. Although all the planets in the solar system revolve around the sun and have roughly the same composition, life only appears on the surface of the earth.

Even the elements that make up life, even complex organic molecules, are everywhere in the universe, but so far we have not found intelligent life, nor have we been found or visited by intelligent life.

This shows that the same composition, life is difficult to appear in different environments. Life can appear on the earth, thanks to its suitable temperature, suitable quality, atmospheric pressure, air composition, liquid water and so on, which are all necessary conditions for the existence of life.

At the beginning of science, we thought that these environments on the earth were too coincidental and bad, that there was only one earth in the universe, that human beings were orphans of the universe, that human beings were accidental products of the universe, and that our appearance was attributed to the hand of God.

However, with the development of science and the broadening of human vision, especially after human vision stepped out of the Milky Way in the 1920s, the existence of extragalactic galaxies was discovered. At this time, human beings really realized that our galaxy is just an island in the vast ocean of the universe.

For the first time, I realized the vastness of the universe and the richness of matter, and realized the smallness and insignificance of human beings.

In the 1990s, mankind did a very great thing. In order to avoid the influence of the earth's atmosphere on observing the sky, an optical telescope was launched into the earth's orbit.

In order to commemorate Edwin Hubble's discovery of extragalactic galaxies and initiate extragalactic astronomy, the most expensive telescope of mankind was named after it.

The launch of this telescope directly inserted the wings of human vision. Through the observation of the distant universe by Hubble telescope, we saw the appearance of the universe 654.38+0.3 billion years ago, which gave us a deep understanding of the evolution of the universe, celestial bodies and galaxies.

In addition, Hubble telescope provides us with a preliminary estimate of the number of galaxies in the universe. In 20 12, NASA released a photo of Hubble's extremely deep field of vision, which selected a dark and empty space in the sky.

The size of this space is only one tenth of the whole sky12 million, and only110 of the full moon area. Then the space was exposed for a long time with Hubble telescope and the following pictures were taken.

There are about 10000 galaxies in this photo, and the oldest galaxy is132 billion years old. Knowing that the universe is only138 billion years old shows that Hubble has basically seen the first galaxies in the universe.

So according to this photo, we can roughly calculate that the universe contains about 200 billion galaxies, each of which is similar in size to the Milky Way, and contains many stars and planets, some of which are likely to be able to breed life like the earth.

Our profound understanding of the scope of the universe has profoundly changed our view of the universe. Even though the earth's environment is very special and the probability of life is very low, such a huge base makes us believe that there must be intelligent life similar to human beings in the universe.

So even if we haven't found life outside human beings, no one believes that extraterrestrial life doesn't exist, including the top scientists at present. There is a simple reason. The universe is so big that anything can happen. If only the earth has life, it doesn't make sense in science.

Therefore, human beings have been looking for it. At first, we like to send out radio signals actively, hoping that life can find us, but in the end, we think it is stupid to do so. Also, we have been capturing possible artificial radio signals, but we can't rule out the interference of background noise.

So now our main job is to find livable exoplanets, so that we can not only actively find places where extraterrestrial life may exist, but also lay the foundation for human beings to realize interstellar migration in the future.

Through decades of searching, human beings have discovered more than 4,500 exoplanets mainly by using some scientific methods such as transit method, apparent velocity method and microlens method.

Among these planets are terrestrial planets, woody planets and super-earths similar in size to Neptune and Uranus. You may be concerned, among these planets, are there any planets that are very similar to the earth's environment and suitable for living?

Of course, a recent paper published in Astrobiology shows that scientists have re-listed some standards that a super livable planet should meet, and re-screened more than 4,500 exoplanets according to these standards, and found the best 24 candidate planets.

Let's see what standards the next super livable planet (more suitable for human habitation than the earth) should meet:

This planet orbits a K-class star. Our sun is a G-class star, which is more massive and brighter than a K-class star, but its life span is slightly shorter, with a history of over 65.438+000 billion years.

Judging from the time scale of life evolution on the earth in 4 billion years, the life span of the sun as a G-class star is somewhat short. You know, humans have been around for less than a million years, and now the sun is past middle age.

In another 1 100 million years, due to the intensification of solar nuclear fusion and the enhancement of luminosity, the earth will no longer be suitable for survival because of the high temperature, and the life span of K-class stars can often reach 20 billion to 30 billion years, which can support the evolution of life for a longer time.

Therefore, a G-class star like the sun is not an ideal main star for the birth and evolution of life.

This planet is about 5 billion to 8 billion years old. The earth is around this time. If the planet is too old, it will get cold inside, which will lead to inactive geological activities of the planet and even lose its magnetic field.

If the planet is too young and unstable, it is prone to some major geological disasters or celestial impact events leading to extinction.

The surface temperature of this planet is about 3 degrees Celsius higher than that of the Earth. On the earth, the biodiversity of geothermal rain forest is obviously higher than that of cold region. Coupled with liquid water and humid climate, such an environment is more conducive to the survival and evolution of organisms.

The atmosphere of this planet contains 25%-30% oxygen, and most of the rest is inert gas. Oxygen is a necessity of life, with high oxygen content, and it also plays a vital role in the evolution of living things.

This planet has scattered land and water, and there are many shallow waters and islands. Such an environment is very suitable for life, and the connected continents are prone to drought. For example, the super Pangea continent appeared at the end of Permian, and the drought caused the desert to spread outward from the inland center, leading to the misery of life.

This planet has its own large satellite, the mass is about 1- 10% of the planet, and the distance is moderate, which is between 10- 100 times of the radius of the planet.

The moon, the satellite of the earth, is self-evident for the evolution of life on the earth. Many creatures use tidal effects to live and lay eggs.

The volume of this planet is 10% larger than that of the earth, and its mass is 1.5 times that of the earth. Larger planets can provide more living space and resources for life, and greater mass can also make planets have more atmospheres.

Meet all the above conditions, then this planet is a super livable planet. Obviously, these conditions are much better than the earth. None of these planets screened by scientists can fully meet the above conditions.

However, the overall score of each planet in these indicators is higher than that of the earth, that is, it is more suitable for the survival and evolution of life than the earth.

In a word, they are older, heavier, wetter and warmer than the earth, and their main stars live longer.

Therefore, scientists believe that there is a great chance of life on these planets. Because some of them are older than the earth, it is very likely that there are more advanced civilizations than human beings.

However, these planets are not close to the earth, and they are all light-years away from the earth 100. It seems impossible to go to these planets at present, but these discoveries can help us find extraterrestrial life.

In the future, including NASA's james webb Telescope, Louville Space Observatory and ESA's Plato Telescope, we can study them more extensively, measure their atmospheric composition, and even find potential signs of life activities.

In a word, it is certain that the earth is no longer the only choice for life. There are many paradise for life outside the earth, and the future is waiting for us to discover.