? Why did life arise on Earth and not on other planets
In the hit movie "28 Days Later" released in 2002, the hero Jim, played by Kelia Murphy, wakes up alone in a London hospital, the atmosphere completely random and everything smashed or out of place, clothes, medical equipment, doors and chairs. He goes out into the street and finds no trace of humans. He wanders around the nearby market, gets in the car and travels for several miles, but the same result remains. It seems that something catastrophic has
? happened, where did everyone go
This is the same question that humans have asked since ancient times about our position in this universe, once said the philosopher Metrodoras, a disciple of Democritus, who lived nearly two thousand and five hundred years ago: “It would be strange if there is one ear of wheat in a wheat field, as It is strange that there is only one inhabited world in the extended infinity."
When telescopes appeared, and the German astronomer William Herschel used them in the early nineteenth century, he said that when he looked at the moon and saw its craters with their wonderful symmetry, he thought that they had been designed by the "people of the moon." Mars and Jupiter in the telescope are clouds and water, and that there may be human populations, or others, living in these areas.
But as we invent more technology tools, including robotic vehicles that are now roaming the surface of Mars such as “Perseverance” or “Curiosity”, those perceptions receded until we reached the moment of writing these words, as we have not yet discovered any form of life in our group The solar system or any other star system that we know of, we haven't found even a single bacterial cell.
"where did everybody go?" It is also the question of Enrico Fermi, the Italian-American Nobel Prize-winning physicist. The story begins with an ordinary summer lunch session at Los Alamos National Laboratory, New Mexico, USA in 1950, during which a group of nine physicists discussed the myths of UFOs. The effect of Fermi's question, although at first glance it may seem laughable indeed, the question is deeper than we can imagine.
We live in a universe that was born, as we imagine, about 13.8 billion years ago, with two trillion galaxies, according to the latest studies in this range, each of which contains hundreds of billions of stars. Other than the sun - there are a similar number of planets, some of which have atmospheres similar to our warm Earth's.
In a universe like this, a civilization with medium missile technology could reach the entire boundary of its own galaxy in just 10 million years, at that point let's assume that there is some planet, let's call it "Planet Krypton", similar to Earth in almost everything, was born “Krypton” is about 6.5 billion light years ago, while the Earth was born from the inside of the dust cloud surrounding the sun only 4.5 billion light years ago. This means that Krypton is now two billion years ahead of us.
Here we will ask: When did man invent writing, about five to seven thousand years ago, for example?! All of the industrial progress we see was 200 years ago, and just 20 years ago we would not have expected that 6 billion people on this planet would own a mobile phone. The evolution of humankind's technical capabilities prompts us, at least, to understand how much progress can be expected if things continue in this fashion.
At this point, the Russian physicist Nikolai Cavendish intervenes to say that there can be three basic levels for any civilization, the first is the ability of civilization to use and store the energy coming to it from the star on which it is basking, and the second is that the civilization is able to make techniques of precision and development so that it can be It can completely envelop its star to exploit every atom of its energy, and the third is for civilization to be able to use and store all the energy of its own galaxy.
For us terrestrials, we are still struggling to become one day in the first level, while the planet Krypton may now be in the third level, here appears the "Fermi Paradox" which asks: Despite all these possibilities and enormous potential, why then did that civilization not come us? Where did life go? Why are we alone like this? This question simply gives two answers, either they are only found in the “Marvel” and “DC” films, and we are alone until the drunk, or they are already there, but for some reason we cannot communicate with them.
In the 1970s and 1980s, American astronomers Carl Sagan and Frank Drake argued that the Earth is a typical, very ordinary planet, with billions of similar planets in our galaxy alone, and thus presents us with great "possibilities" for the existence of intelligent life in The universe, that's basically what fueled the Fermi Paradox, because the possibilities are great and we haven't seen anything yet.
The duo relied on a set of simple foundations to support their argument, for example, what we now know as the habitable zone, which means the region around the star in which a planet can contain water in its liquid form, not close to the star so that the water evaporates, or far away and freezes, we know Already about 70 planets in these conditions currently.
But in the eighties of the last century, both the Americans Peter Ward, a paleontologist, and Donald Brownlee, an astronomer, suggested that the matter is more complicated than that, for example, we will assume that a planet, called “X”, arose in the habitable zone around a sun-like star. , but it was close to the center of the galaxy, here it will be difficult for life to arise on it, because the closer we get to the center of the galaxy, the closer we get to the black hole in the center of the galaxy, and the neutron stars surrounding that region, and the radiation from these bodies is enough to end life on this planet .
On the other hand, this region is crowded with stars, which means that there is a possibility that one of them will pass close to this new sun around which “X” revolves, disrupting its orbit, and thus the life arising on its surface is affected, or perhaps completely destroyed, if it originated from the foundation.
But if the star is located at the outer edges of the galaxy, this means that the proportions of minerals - such as carbon, sulfur, or others - are few in it, because the closer we get to the center of the galaxy, the more the stars are fed with minerals, and accordingly, this means that there will not be enough quantities From the minerals in this star to create rocky planets on which life can arise using these elements.
At that point, what we call the “habitable galactic zone” appears, and it means that there is a very specific strip of possibilities for the emergence and continuation of life in the Milky Way, or any other galaxy, and this undoubtedly reduces the chances of the existence of sane life in our galaxy significantly, but there Which makes the task more difficult than you can imagine.
The idea is not that life arises only, but that it also evolves, that is, that it flourishes and diversifies over billions of years, and that means that life finds an opportunity to settle. It revolves around the sun with several forces. In addition to the sun’s gravity, there is also the gravity of other planets, especially the giant ones such as Jupiter. These gravitational forces directly affect the Earth’s orbit and the tilt of its axis, which now stands at 23.4 degrees.
Similarly, the moon, due to its relatively large size compared to the planet Earth, plays a role in maintaining its tilt, it is like two ice dancers, when each holds the other's hands, they maintain each other's balance, compared to the case in which each dances alone, as is the case with the Earth and the Moon, which is why they are often called the "Earth-lunar system".
Mars, for example, does not have this feature, because its two moons are very small relative to the planet, "Deimos" with a diameter of only 15 kilometers, and "Phobos" with a diameter of 25 kilometers, so the planet is not fixed in its tilt due to the attraction of the nearby Jupiter, and it often changes its inclination (it takes It is hundreds of thousands of years), but a slight change in the tendency hits the climate completely, and thus threatens the stability of life, as sunlight is concentrated on the surface of the planet in areas without others with each change, and thus the values of temperature and coldness and the climate system change drastically, the climate may be Too wet and then become too dry, or the desert landscape may turn into a rainforest, etc.
The matter does not stop only on Earth, but it has to do with all the components of the solar system, and to understand this complex point, let us reflect on what the science of searching for planets outside the sun has reached so far after the discovery of more than 4,000 planets, as it appeared that the form that the solar system is currently taking is rare. , or say "unusual", giant planets are usually close to the star they orbit (not as far away as Jupiter), and rocky planets are usually larger than Earth and its companions, in this case called Super Earth, and stand in size Between Earth and Neptune.
What happened in our case then? Researchers in this range imagine that at the beginning of the history of the solar system, 3 rocky planets were formed that are larger than the Earth in size and mass (super-Earth). to a region close to the sun, and by his presence destroys the planets that were in that region, and stops in their place.
But in the particular case of Earth, Jupiter has been subject to the so-called "Grand tack hypothesis" which says that after Jupiter formed 3.5 AU from the Sun (an AU is about 150 million km), the planet migrated inland To a distance of 1.5 AU from the Sun, before it reverses its course and returns again to a distance of 5.2 AU.
This happened because of the appearance of Saturn in the background of Jupiter, and they were gravitationally linked together, and Saturn was able to prevent Jupiter from moving forward to destroy the region of the rocky planets permanently, and attracted him back again, but when Jupiter approached the region of the rocky planets, it caused a severe confusion between its planets, and it collapsed and the result was Formation of 4 smaller rocky planets than the 3 large ones.
Does this mean that the presence of the planet Saturn was essential for the emergence and stability of life on the surface of the Earth, or that the presence of two giant planets in the same model is necessary to maintain life on a third planet closer to the star? It is a very important question in the context of our conversation about the chances of life on other planets, especially when we know that Jupiter’s travel abroad again caused additional confusion to the snowy rocks surrounding it, which is rich in water, because of that, millions of strikes were launched that the Earth received in that period, and the reason was In getting our planet a hundred.
But this precious water would not have remained on Earth for four and a half billion years had it not been for the tectonic plates, which is the constant movement of pieces of the earth’s crust towards each other. In eastern Africa, they slide against each other and make volcanoes, and all of that was recycling water and carbon dioxide, and with them the elements necessary for life, over billions of years.
Do we find in the solar system planets that contain moving tectonic plates? Unfortunately not, Mars is thought to have been that way once, several billion years ago, which actually helped it conserve water and possibly plants and life, but it has stopped. Also, we only have limited techniques to reveal to us how common plate tectonics is in planets around other stars.
All this while we are only talking about the possibility of life on the surface of a planet, and we have not yet touched upon life itself, its genesis, evolution and diversity. It is enough for you to know that a team from Cardiff University in Britain had examined several years ago two remnants of massive star explosions (supernovae). To find that the percentages of phosphorous in them are very weak, which affects our perceptions of the commonness of life, of course.
Phosphorous is one of the six essential elements found in the DNA of living organisms (adenosine triphosphate), and therefore its scarcity means, in turn, a scarcity in the existence of life itself, and of course here we are talking about images of life as we know it, but at that point it must be clarified That life "as we know it" may also be the easiest, and therefore most bearable, form of life.
To understand that idea, let's consider, for example, the difference between a carbon atom and a silicon atom, both of which can have places that accept four chemical bonds. One (Imagine the difference between the chances of a four-place lego piece and a two-place piece serving as the framework for his adoption figure).
But compared to silicon, carbon bonds are more flexible during their interaction with other chemical elements, and therefore this gives a greater opportunity for better chemical reactions, and this means a better chance for the emergence and diversity of life, which is - in an abstract - a picture of complex and flexible chemical reactions, and therefore the forms of life Carbon-based have a better chance of being in this universe than silicon-based forms of life, if they could exist at all.
Well, all of the above, a set of examples among many more, feed into a hypothesis proposed by Ward and Brownlee called the Rare Earth hypothesis, which holds that the existence of life on a planet requires a large number of complex factors, some of which are rare , all of which greatly reduce the odds of life appearing in the universe, consistent with an earlier hypothesis proposed by Robin Hanson, professor of economics at George Mason University.
Robin's hypothesis confirms that any civilization starts from a star and a planet in the habitable zone, but this is only its first condition. The emergence of reproduction by mating, then the emergence of multicellular organisms, then a creature being able to use its brain, then the stage in which we humans are now, and finally the ability to colonize other planets and penetrate into the sides of the galaxy, or the entire universe.
But what if one of those conditions represents a real and not easily surmountable deficit in the way of any form of life? This inability is called the Great Filter, and it may be a primary cause, such as the emergence of life, or a cause that occurs in an advanced stage, such as the large percentage of civilizations destroying themselves while passing our stage (in which we are now) to a stage of greater civilizational progress that allows colonizing other planets.
From this point of view, the Earth was either among the very few planets lucky to pass through that delicate refinery several million / billions of years ago, or it may be on the verge of a cosmic or civilizational catastrophe. Or a Russian, for example, we may have survived previous wars, but do we guarantee that we will survive in the context of a tremendous development in the sciences of war, and have our minds developed enough to adapt to all this?!
When Enrico Fermi asks: “Where has everyone gone?” Ward, Brownlee and Mason answer: “Not all are as you think,” but it is not the only answer. Other assumptions suggest that these civilizations exist but do not want to communicate with us for many reasons, either we Too primitive, or the matter is economically costly and the results are not good behind it, on the other hand, the size of our observational techniques do not enable us - by an astronomical standard - only to look before our eyes in the galaxy.
According to the "Drake statistical equation", there can be about 4,590 intelligent civilizations in our galaxy, and assuming that they are all located at the same distance from each other, this makes the distance between each of them 28 thousand light-years, and if you add to this the optimism limits of the equation That distance would reach a number between 1361-3979 light years, while the farthest extent of our human telescopes is only 500 light years, yes, they may be up there but we haven't been able to spot them yet
In the end, all the hypotheses we have presented do not fall within the scope of experimental science in the understandable sense, but it raises important questions. There may be no one in the universe and we are only completely alone, or say: “We may be the first experience of this universe with rational life in its history,” but whether that is true and that we are actually alone in that vast cosmic expanse, or it is not true And there are indeed other lives that we haven't discovered yet, the matter - in both cases - causes panic.....
Source: websites