In the Search for Life beyond Earth, the Only Constant Is Hope
In The Italian astronomer of the late 1800s, Giovanni Schiaparelli, pointed out a telescope on Mars and saw something curious: linear characteristics he called canalimeaning “channels” or “grooves”. A bad translation of this word contributed to a generalized belief that the planet closest to the earth has hosted a civilization.
The American astronomer Percival Lowell took the observations of Schiaparelli and ran with them. He became obsessed with Martian brands, which he interpreted as evidence of a sophisticated network of water transport channels. “That Mars is inhabited by any or other beings that we can consider as some because it is uncertain what these beings can be,” wrote Lowell in his 1906 book Mars and its canals.
It seems ridiculous now, but it was not at the time. At the time, life ideas were playing quickly, explains David Baron, author of the new book The Martians: The True Story of A Alien Engoust that captured America at the beginning of the century. In 1858 Charles Darwin published his theory of natural selection. A year later, German scientists Robert Wilhelm Bunsen and Gustav Robert Kirchhoff invented the spectroscope, which they and others used to analyze chemical signatures in sunlight and planets. These studies have revealed that other worlds are made of the same elementary constituents as the earth. If life evolves through a natural process and all planets are formed in a similar way, why does life not also settle on the red planet?
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More than 100 years later, scientists looking for extraterrestrial life are guided by the same reasoning: the universe is vast, and everything is done with the same basic things as we are, so why wouldn’t it be life elsewhere? However, the evidence of intelligent life beyond the earth took several laps. In fact, the only constant was hope: the desire that many people must prove that we are not alone. The question of the existence of extraterrestrial life is not only a neutral scientific debate – this counts for humans, including humans in search of this life. And our optimism that we see that it tends to turn around and move.
The idea that Mars houses civilizations that laughed at the canal began to lose its radiance in 1909, when the French astronomer Eugène Antoniadi observed the red planet during one of his narrow biannual approaches. The lines, he found with a better telescope and a more intimate view, were an optical illusion. These data did not convince Lowell, and that did not put the theory at rest – in 1916 American scientist Waldemar Kaempret editor was still convinced that the channels were real. However, belief in advanced life has faded during the following decades. When the Spatial Mariner 4 flew by March in 1964, relaying the images of a dry and sorry world, the Martian hypothesis died for good.
And the signs were not promising for extraterrestrials elsewhere either. In 1950, the Enrico Fermi physicist had pointed out what he called “great silence”: if life is likely to be abundant, then where is everyone? The fact that humanity has not heard of other intelligent beings has become known as Fermi Paradox. Perhaps life is common, but advanced life is rare, have suggested scientists. Or maybe other civilizations often arise and then destroy themselves, because humanity seemed newly capable of doing after the invention of the atomic bomb in 1945.
Astronomers began a more systematic study of the issue. In 1960, the researcher at the University of Cornell, Frank Drake, launched the Ozma project, which used a radiotelescope to search for emissions from two distant star systems. In 1977, astronomers caught a lot of radio waves that exploded for 72 seconds, more like an extremely powerful cosmic radio station than something natural. They called it WOW! Signals and excited. But the same transmission has never been heard again. Until now, the search for extraterrestrial intelligence (SETI) has not found convincing evidence of dissemination of foreigners.
However, in recent times, there have been new reasons to hope. In 1992, astronomers Aleksander Wolszczan and Dale Frain discovered two rocky worlds surrounding a dense and rotary star called a pulsar. Although these planets are bombed with too much radiation to be habitable, more exoplanet discoveries flowed in the 2000s. Then, the Kepler space mission was launched in 2009. It revealed thousands of worlds beyond it, with more than 5,900 in total confirmed from the publication period. “The planets have become the rule, not the exception,” explains Nathalie Cabrol, director of Carl Sagan Center for the Study of Life in the Universe at the Seti Institute.
This wealth of worlds has once again changed the calculation on the probability of life beyond the earth. In 1965, Drake developed a formula to calculate the chances of communicating with extraterrestrial civilizations. He has taken into account the rate of stars’ formation, the fraction of stars with planets, the fraction of those who are habitable, the proportion of habitable planets which really develop life, the proportion of this life which becomes intelligent, the fraction of civilizations which develop the technology of communications and the duration of the time that they are likely to transmit. Most of these variables were unknown at the time – and are still – but the exoplanet boom helped reduce the second variable, and it makes progress on the third. We now have a much better idea of the number of host stars of the planets, and it is at least most of them.
We still don’t know how life has started here on earth, so we don’t know how it could happen elsewhere. And we do not know how much the advanced civilizations are likely to destroy themselves – an urgent question for reasons beyond Seti. But we now know that primitive life can prosper in deeply inhospitable conditions, which means that microbial foreigners can be much easier to find than intelligent.
In 1966, the environmentalist Thomas Brock discovered the first end, Thermus aquaticus, Live in hot Yellowstone swimming pools. Since then, scientists have found microscopic organisms in hydrothermal vents at the bottom of the ocean and in toxic mine waste, in the interiors of rocks and radioactive water. It is not because a planet looks sterile that it is. There are good reasons to think that primitive life could survive in the buried oceans of the Moon of Jupiter Europa and geysers of Enceladus, a moon around Saturn. There could even be microbes in the pools of melting water under the glacial caps of Mars. More than a century after Percival Lowell and its illusory Martian civilization, science has given us many reasons to think that we are not alone, even if foreigners prove to be cell organisms rather than architects of construction of the canal.
