Dreams of other sentient beings have always haunted us. So far, no trace of it has been found. Searches for extraterrestrial life using a variety of techniques do not yield results. If we can, what are the chances of finding someone similar to us? They are very small.
1. Gravity
Earthly life has adapted to the available gravity. It should be taken into account that it will not be the same on all planets. And it's not only the size of the habitat, but also its density.
The force of attraction affects the structure and development of beings. This can be traced even on the example of the development of life on Earth. When organisms went on land, they needed a skeleton and other limbs, since in water it is not required in this form.
Gravity affects the appearance of organisms.
If the planet's gravity is 2 times higher than the earth's, then a noticeable reorganization of the body will occur. People will not be very comfortable in such an environment. The bones should be significantly thicker and lower in height.
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2. Atmosphere
The percentage of oxygen in the atmosphere can significantly affect the shape and size of living organisms. So, in the history of the Earth there was a period when there was more oxygen.
Arthropods that lived 300 million years ago, due to this, grew larger. The ancestors of scorpions could grow up to 70 cm in length. And that's only 14% of this gas in the atmosphere. And if it is much more or less?
The atmosphere of different composition affects the living in different ways.
Imagine how this could affect the shape of the creatures. Or, if there is no oxygen in the atmosphere, but there are other substances. If life is possible in such conditions, then it is completely difficult to imagine the variety of organisms.
3. Basis
On Earth, the key element of life is carbon. Thanks to him, complex connections are formed that allow the transmission of hereditary information. We have not yet met another version of the foundation of the living.
Ammonia as the main element of living things?
Sagan and Hawking called this phenomenon "carbon chauvinism." Scientists, however, have suggested that carbon substitution is possible under certain conditions. Thus, the most promising elements are ammonia and silicon.
Yes, they are less common than carbon, but on individual planets conditions may coincide in such a way that there will be a sufficient number of them. And the forms of life will significantly differ from the earthly ones.
4. Time
The evolution of the mind takes a long time. Life on our planet is more than 2 billion years. And the Universe, as you know, is more than 13 billion years old.
If we assume that life somewhere originated at that time, then by the current moment it could have outstripped the development of people so much that we would be ants against their background.
In years we will develop to this point.
The question arises: why did they not yet appear to us, because they certainly know how to travel between the stars? Most likely, they are simply not interested in us, so far from their level.
5. Robots
Despite the fact that the biological form of life seems to us the most promising and convenient, one can argue with this. So, Seth Shostak, director of the center for the search for extraterrestrial life, says that biological life has a number of disadvantages compared to robotic.
It's more profitable to be a robot.
It is assumed that a highly developed civilization will eventually begin to "pump" itself with mechanical and electronic devices. As a result, she will completely abandon the body, turning into robots.