Why exactly the earth?
In the meantime, about the Earth, perfectly prepared to become our cradle. We were lucky. On earth, several favorable circumstances for life coincided. Not every star becomes a Sun surrounded by planets. Should the nebula rotate more slowly, centrifugal force would not have arisen, fragments would not come off from the central clot, planets would not have arisen. And such a lonely “childless” star would swim in a black abyss, barrenly wasting its heat and light … Not every star that gave birth to planets could create conditions suitable for the birth of life on them. It takes a lot of time, billions of years, for the origin and development of life. All this time the star should burn evenly, calmly, equally. Then the conditions on the planet will be constant – and life will be able to adapt to them. But the stars are far from being not all as calm as our Sun. Young stars sometimes flare up. A wave of incinerating heat hits the surrounding planets, burning, evaporating everything that can burn and boil. Life on the planet after such a fiery hurricane will certainly perish, and on an empty bare ball it will be necessary to start all over again. To develop life, you need a calm star. Our Sun is a calm star. But put our Earth closer to the Sun, for example, in the place of Mercury or Venus. From the unbearable heat on the Earth, oceans cannot even form. Water will boil immediately. What life is there. Move the Earth farther from the Sun, somewhere in the region of Jupiter. Life will not arise either. Water – the basis of life will always be frozen there. We were lucky in that the Earth’s orbit is circular, but it could be elliptical. Just imagine that the Earth is approaching the Sun so close that all the water from its surface evaporates, then it is removed so far that the water, having fallen from the atmosphere back to the Earth, freezes through. Through a “comfortable” place, where the temperature is “just right”, it sweeps twice a year with such swiftness that “there is no time to do anything.” There is simply no time for the birth and development of life. Such heat-cold can be not only due to the ellipticity of the orbit. There are “double stars”. Then, in any orbit, the planet cannot always be at an equal distance from the heat source. One sun is close, then the other, then both are far away. We were lucky in terms of the size of our planet. If it is smaller, for example, the size of the moon, do not hold on to its atmosphere. This means that water, inclined to evaporate, passing into the atmosphere. No matter how many volcanoes throw more and more portions of gases and water, all this will quickly disappear into space. On the Moon, therefore, there is no atmosphere, no water, no life. The Earth is also inconvenient for life, the size of, say, Jupiter. Inconvenient due to too much attraction. Such a large “Earth” will hold a layer of a very dense atmosphere, containing also hydrogen and helium, which are unfavorable for the occurrence of life. A thick layer of very dense clouds will create eternal darkness on such a planet. And without life-giving sunshine what life can be? In a word, when we look at the sky strewn with stars, we must not forget that, firstly, probably not all stars have planets, and secondly, not all planets are suitable for life. But … there are about 100 billion stars in our galaxy, and surely there are enough planets in it like Earth.
The origin of life (hypothesis of A.I. Oparkin)
Long before we make contact with other intelligent beings living somewhere in the galaxy, we must understand not only the place we occupy, but also the long path we traveled.
So, before us is planet Earth. She has an ocean. Imagine it. The rivers flowing into it, first flow along the slopes of the mountains, crumbling rocks along the way, and all that they can carry with them into the ocean. The atmosphere above the ocean is saturated with volcanic gases, dust, ash. Waves, scattered by the spray, take it all to their depths. As a result, the water in the primeval ocean is bitter-salty, turbid. She is a real “broth”, so much is mixed and dissolved here. Here you can find almost all the elements of the periodic table. Especially a lot of those that are necessary to create living things. Warm water provides molecules and atoms with good mobility, mixing, and contacts in various combinations. But this is not enough for chemical reactions. For them, “external” power is often needed. A push from the outside can help atoms and molecules to connect, can break molecules into pieces. Chemists often use heat to speed up reactions. Nature acts in a similar way. For this, not only particles of light – photons, but also “cosmic rays” – fragments of atoms ejected by distant stars that work all day round through the atmosphere and pierce into the ocean. Their impacts are especially strong and are more suitable for breaking molecules.