The life may depend on the galaxy

Intelligent life on other planets may not be as improbable as many scientists believe, according to a new study that challenges a widespread anti-ET argument.

Many skeptics are limited to an idea called anthropic argument which holds that extraterrestrial intelligence should be very rare because the time needed for intelligent life to evolve, on average, much higher than the period in the existence of the star that allows that such a life to flourish.

But now astrobiologist Cirkovic Milan and his colleagues say they have found an error in this reasoning.

The anthropic argument, proposed by astrophysicist Brandon Carter in 1983, following his pioneering work on the anthropic principle in 1970, is based on the assumption that the two periods, the life cycle of a star and the time required for and evolution of life-intelligent creatures are completely independent. If this is true, Carter argued, it is highly unlikely that these periods have the same duration and occur simultaneously.

But this way of thinking is obsolete, says Cirkovic. In fact, he says, are not independent, but are deeply intertwined. “There are many different ways that the planets of our solar system are not isolated,” says Cirkovic. “Do not think for habitable planets like closed boxes. If we abandon the hypothesis of independence, then we have a new fund in which you can configure various development models astrobiology.

Cirkovic indicated gamma-ray bursts in the vicinity of supernovae, and disturbances in the cloud of comets as possible astrophysical events in the environment of a star that can influence the biological development of a planet. For example, when a star travels through one of the dense spiral arms of the Milky Way, both its own development and that of their planets would be disrupted by the increased levels of electromagnetic radiation and interstellar cosmic rays, because higher frequency of star forming regions and supernova explosions.

All these connections conspire to rule out independence proposed by Carter and connect the life of a star with the evolution of life on a planet, argues Cirkovic.

Earth fortunate
In the case of Earth, the two periods have been aligned to allow life randomly. Our sun has an approximate age of 4,600 million years, and the Earth is slightly lower, something like 4,500 million years. Most of the basic cells are believed to have formed on our planet about 3,800 million years ago, although the genus Homo, to which humans belong, did not appear until about 2.5 billion years ago. And modern humans have only 200,000 years old.

For more than eighty percent of the existence of the sun, life has existed in some form on Earth. Apparently, the periods of biology and astrophysics have aligned favorably in our case. According to the anthropic argument, this coincidence means that the Earth, and their lives are unique. But Cirkovic think the two periods could not have been superimposed by chance. Instead, they can be part of a complex history, including the interdependence of the Earth with the rest of the Milky Way.

Timing disasters
The cosmic events like gamma ray bursts and nearby supernovae astrobiological could reset the clock to give them to a planet and its star a second chance to sync and try again produce life. Gamma-ray bursts are mysterious explosions that release large amounts of energy, produced either by the death of super-massive stars (like Eta Carinae) or the collision of neutron stars in binary systems. If a gamma ray burst occurs in a region close to a planetary system, causes an increase in intense radiation and possibly cosmic ray jets could disrupt life on planets. Supernova explosions, although not as energetic as those of gamma rays (but much more common in general) can send an energy boost to any nearby planet.

“A burst of gamma rays will not affect the particular time in life to be born, but affects the speed with which life develops or is maintained by causing changes in atmospheric chemistry of the planet,” says Cirkovic. “This can be interpreted as astrobiology reset the clock every inhabitable planet in the Milky Way”.

This idea leads to new thinking on the origin of life. Instead of a long and gradual evolution, a catastrophic event would stimulate the development of a complex biosphere and intelligent beings, such as evolutionary theory of punctuated equilibrium predicts that species will be subjected to long periods of slow evolution punctuated by brief episodes of change drastic.

For example, paleontologists say that human beings evolved to our current state only because of an asteroid impact 65 million years ago, which swept the top predator on the planet: the dinosaur. Earth during the course of its history has experienced many mass extinctions that took several causes. While claiming the lives extinctions are also a button “reset” that alters the environment and can be other types of life. In general, this is part of a complex set of stories that Cirkovic astrobiology and his colleagues have dubbed “the landscape astrobiological” of our Galaxy. “The speed of evolution is very variable,” says Cirkovic. “There is no reason to think that life on Earth only has a single origin. It is quite possible that life on Earth has had several beginnings.”

Cirkovic also indicates that the evolution of intelligent life could occur slower or faster, and is not necessary that you follow the history of the Milky Way astrobiology.

“Large-scale correlations that could generate more SETI targets are contemporaneous with us than would be expected only on the basis of the global age distribution,” says Cirkovic.

Source: Astrobiology Magazine
Author: Clara Moskowitz