Life is pretty easy to learn. He moves, he grows, he eats, he secrete, he multiplies. Simply. In biology, researchers often use the abbreviation "MRSGRENDescribe it. It refers to movement, breathing, sensitivity, growth, reproduction, excretion and nutrition.
Although life can be easily recognized, it is actually difficult to define, and scientists and philosophers have argued for centuries, if not millennia. For example, a 3D printer can reproduce itself, but we would not call it alive. On the other hand, the mule is famously barren, but we would never say that he does not live.
As no one can agree, there are more 100 definitions that life is an alternative (but imperfect) approach describes life as a "self-sustaining chemical system capable of Darwin evolution" that works in many of the cases that we want to describe.
Lack of definition is a huge problem when it comes to finding life in space. Failure to define life other than “we will know it when we see it” means that we really confine ourselves to geocentric, perhaps even anthropocentric ideas about how life looks. When we think of aliens, we often portray humanoid creatures. But intelligent life we are looking not necessarily humanoid,
Life, but not as we know it
Sharman says that she believes that aliens exist, and "there are no two ways." Moreover, she wonders: “Will they look like you and me from carbon and nitrogen? Probably no. Perhaps they are here now, and we simply cannot see them. ”
Such a life will exist inshadow biosphere". By this I do not mean the realm of ghosts, but undetected creatures, probably with a different biochemistry. This means that we cannot study or even notice them, because they are beyond our comprehension. Assuming that it exists, such a shadow biosphere is likely to be microscopic.
So why didn’t we find it? We have limited opportunities to study the microscopic world, since only a small percentage of microbes can be cultured in the laboratory. This may mean that there really can be many life forms that we have not yet noticed. Now we have the opportunity to sequence the DNA of uncultured strains of microbes, but this can only detect the life that we know – which contains DNA.
However, if we find such a biosphere, it is not clear whether we should call it a stranger. It depends on whether we mean “extraterrestrial origin” or simply “unfamiliar”.
A popular alternative biochemistry proposal is based on silicon, not carbon. This makes sense even from a geocentric point of view. About 90% of the Earth is made up of silicon, iron, magnesium and oxygen, which means there are many opportunities for creating potential life.
Silicon looks like carbon, it has four electrons available to create bonds with other atoms. But silicon is heavier, with 14 protons (protons make up the atomic nucleus with neutrons) compared with six in the carbon nucleus. Although carbon can create strong double and triple bonds to form long chains, useful for many functions, such as building cell walls, silicon is much more complex. He fights to create strong bonds, so molecules with long chains are much less stable.
Moreover, conventional silicon compounds, such as silicon dioxide (or silicon dioxide), are typically solid at terrestrial temperatures and insoluble in water. Compare this, for example, with highly soluble carbon dioxide, and we will see that carbon is more flexible and provides much more molecular possibilities.
Life on Earth is fundamentally different from the basic composition of the Earth. Another argument against the silicon-based shadow biosphere is that there is too much silicon in the rocks. In fact, the chemical composition of life on Earth has an approximate correlation with the chemical composition of the Sun, with 98% of the atoms in biology consisting of hydrogen, oxygen and carbon. So, if there were viable life forms of silicon, they could have developed elsewhere.
However, there are arguments in favor of silicon-based life on Earth. Nature is adaptable. A few years ago, scientists at the California Institute of Technology managed to remove the bacterial protein that created bonds with silicon – essentially the embodiment of siliconThus, in spite of the fact that silicon is inflexible compared to carbon, it could possibly find ways to assemble into living organisms, potentially including carbon.
And when it comes to other places in space, such as the moon of Saturn Titanium or planets orbiting other stars, we, of course, cannot rule out the possibility of life based on silicon.
To find it, we must somehow think outside the framework of terrestrial biology and find ways to recognize life forms that are fundamentally different from carbon-based forms. There are many experiments testing these alternative biochemicals, such as those from Caltech.
Regardless of the belief of many that life exists elsewhere in the universe, we have no evidence of this. Therefore, it is important to consider life as precious, regardless of its size, quantity or location. Land supports the only known life in the universe. Therefore, no matter what form life may take elsewhere in the solar system or the universe, we must be sure that we will protect it from harmful pollution – whether it be earthly life or alien life forms.
So can aliens be among us? I do not believe that we were visited by a living form with the technology to travel through vast outer spaces. But we have evidence that carbon-based life-forming molecules arrived on Earth. meteoritesThus, evidence certainly does not preclude the same possibility for more unfamiliar life forms.