Why do scientists always assume that the form of life is carbon based life?
There are always friends who say that scientists’ theory of defining life is so narrow that all life forms on earth are composed of 25 chemical elements. Are there any other forms of life in other parts of the universe that are far beyond our imagination? Are they still cellular creatures? Do they have the same shape and size as us? Whether they can get into four-dimensional space.
This is about the imagination of life and intelligent form, which will suddenly burst like a flood. First of all, the definition of life should be a complex and selective material exchange with the surrounding environment. At least that’s how it should have been before a species had a technology explosion.
Secondly, we need to know that the constitution of life is actually formed by the most basic elements. At this point, the elements of the whole universe are certain. There is no difference in the physical properties of the same elements. All matter was born at the moment of the big bang. Each of our atoms was once the dust of the universe, and will eventually be attributed to dust. Then the birth of life is also combined from these known elements. So as to form a more complex chemical structure.
So how do you combine elements to form compounds, or even more complex organic compounds?
As we all know, the lighter an element is, the less electrons it has in its outer layer, and the less complex matter it can form. But because the outermost electrons are very close to the nucleus, it is easier to combine with other elements. So if there are more electrons in the outer layer of heavy elements, will there be more combinations? And give birth to a more complex compound structure, so as to give birth to life?
The answer, of course, is No. There are so many electron layers in heavy elements, the distance between the outermost electrons and the nucleus is also far away, and the electromagnetic force caused by the positive and negative charges between the protons and the outermost electrons in the nucleus is correspondingly weakened. Its covalent bond is very unstable, which makes it less likely to form complex compounds with other elements. Moreover, with the increase of the number of electron layers, elements have become metal elements which are easy to lose electrons.
Now we find that there are few basic elements that can form life. Because of the structure of the four outermost electrons of carbon and the fact that the eight outermost electrons of all atoms are the most stable, carbon atoms can form four stable covalent bonds.
This is the number and limit of chemical bonds formed by elements. This feature enables carbon atoms to form long carbon chain molecules while carrying various functional groups with complex functions to the maximum extent. For example, benzoate or other large carbon chains have more stable structures like carbon carbon double bonds, which is the basis for the formation of complex organic macromolecules. The complexity of this molecule is also the guarantee for organisms to realize various complex functions.
Then there is silicon, but considering that silicon has one more layer of extra nuclear electron layer than carbon, its covalent bond is far less stable than carbon. For example, if carbon carbon bond is American captain pulling helicopter, then silicon silicon bond is normal person pulling helicopter.
Therefore, in the competition of life or the formation of macromolecules, it is not as competitive as carbon based life.