Does the Milky Way really have 36 extraterrestrial civilizations? There’s no definitive answer yet.

Beijing time on June 19 news, in the Milky Way’s spiral arm of hundreds of billions of stars, how many extraterrestrial intelligent civilization? A new study gives the result: 36. The study assumes that Life on Earth represents to some extent the way life evolves in the universe, and believes that intelligent life was born on a rocky planet that is at a proper distance from a star and has evolved for about 5 billion years.

Does the Milky Way really have 36 extraterrestrial civilizations? There's no definitive answer yet.

  A new study assumes that Life on Earth represents some extent the way life evolves in the universe, arguing that intelligent life was born on a rocky planet at a proper distance from a star and has evolved for about 5 billion years.

If this assumption is correct, humans may not be the only intelligent life in the Milky Way, but because they are so far away, we have not yet met other neighbors.

Seth, a veteran astronomer who worked at the Institute for the Search for Extraterrestrial Civilizations in Mountain View, California, was not involved in the new study. Another major hypothesis of the study, he says, is that life evolves in all parts of the universe with the same timeline as Earth, meaning that seemingly accurate calculations are actually misleading.

“If you relax the conditions of these very big assumptions, you can get whatever you want,” Shostak said.

Faraway neighbors.

Of course, whether humans are the only question of intelligent life in the universe, there is no definitive answer for a short time. But in 1961, astronomer Frank Drake proposed a way to estimate the number of extraterrestrial civilizations, the famous Drake equation. This equation determines whether it is possible for humans to find extraterrestrial intelligent life (or be discovered) based on different variables. These variables include the annual rate at which stars form in the Milky Way, the ratio of stars to planets, the proportion of planets that form ecosystems to all planets, and the proportion of planets that evolve life. This could be further narrowed to include more variables, such as the proportion of planets that produce intelligent life (rather than simple algae) of all planets, and the proportion of planets that develop communication capabilities (which can be detected from space) (humans fall into this category, since humans have been using radio waves for nearly a century).

The last variable is the average time it takes to communicate with alien civilizations. The Milky Way is about 14 billion years old. If extraterrestrial civilizations with high levels of intelligence and interstellar communication capabilities can last for up to a few hundred years, then the opportunities for communication between the Earthlings and them are woefully diminished.

It is not possible to solve the Drake equation because the values of most variables are unknown. However, Christopher Conselice, an astrophysicist at the University of Nottingham in the UK, and his colleagues are interested in using new data on star formation and the existence of exoplanets. Exoplanets are planets orbiting other stars outside the solar system. In the June 15 issue of the Astrophysical Journal, Conselis published their findings.

“A few years ago, it was impossible to write this paper, ” Says Conselis. The team calculated the age distribution of stars in the Milky Way, looking for stars at least 5 billion years old, a time span that may be enough to form a human-like civilization. They found that 97 percent of the stars in the Milky Way are more than 5 billion years old. ‘We’re in a 4.5 billion-year-old solar system, relatively new in the Milky Way, so it makes sense to have a lot of older stars in the Milky Way, ‘ Mr. Conselis said.

The researchers then calculated the number of stars with sufficient density and stability in planetary systems. About one-third of stars over the age of 5 billion are eligible. Next, using current astronomers’ knowledge of the distribution of exoplanets, the researchers estimated the number of rocky planets in the habitable zone of these stars. They also calculated which stars had enough metal content to provide the necessary elements for the rocky planets orbiting them to build various infrastructures, such as radio transmitters. Finally, they set the life span of a civilization with communication capability to 100 years, based on the Earth’s timeline, which has so far used radio technology.

What’s the result? The researchers found that if life on other planets had evolved in the same way, there should be 36 intelligent alien civilizations in today’s Milky Way that can communicate with humans. However, this valuation is uncertain, with the number of extraterrestrial civilizations ranging from four to 211. If extraterrestrial civilizations are distributed roughly evenly throughout the Milky Way, our nearest neighbor may be 17,000 light-years away.

Such a distance means that we are unlikely to contact them. The researchers calculated that it would theoretically take about 3,060 years for detectable signals broadcast by extraterrestrial civilizations to be received by us. In other words, to establish a two-way dialogue with such an alien civilization, humans (and aliens) must maintain the continuation of civilization for at least 6,120 years.

Questioning assumptions

The researchers also came up with a more optimistic vision for the search for extraterrestrials. For example, if life evolves intelligent civilizations at any time after 5 billion years, not necessarily 5 billion years, the number of civilizations that may exist in the Milky Way will rise to about 928. In this case, it only takes 1030 years for an extraterrestrial civilization to get in touch with us.

The problem with these estimates, says Mr Shostak, is that the study authors filled some of the gaps in Drake’s equation with astronomical data, omitting some of the most complex and controversial variables without much discussion. Will life really evolve on any rocky planet within the habitable zone of a sun-like star system? Will intelligent life evolve 4.5 billion years after its birth? If no asteroid had hit Earth 66 million years ago, leading to the extinction of the dinosaurs, the evolutionary timeline of intelligent life on Earth would have been completely different. Perhaps the most limiting variable, Shostak argues, is one of the assumptions: that a civilization that can communicate only delivers signals in a century. Even for human civilization, he says, such an argument seems too pessimistic. Despite the many challenges that human civilization has faced in recent months, it seems unlikely that humanity will stop using radio waves for the foreseeable future.

The solution to Drake’s equation “depends to a large extent on the possibility of life, the possibility of (intelligent life) appearing on a planet, and the time when intelligent life lasts,” Shostak said. “

According to Conselis, computing is a way of understanding the existence of mankind and its future. If it turns out that there are more civilizations in the Milky Way than the Institute predicts, it means that life can evolve in broader conditions than Earth, or that, to date, extraterrestrial civilizations have tended to live much longer than our human civilizations. “If we find a lot of these planets, that would be a good sign that our civilization may have a long life span, ” Conselis said.

On the other hand, if the search for extraterrestrial life is still nothing, it may mean that life is very rare in the universe, or that when intelligent life appears, they tend to self-destruct quickly. The Milky Way may have been relatively “buzzy” billions of years ago, but those lives have long since been wiped out.

Ultimately, says Mr Shostak, there is only one way to find out. “Only by finding one or two such extraterrestrial societies can you write a paper to estimate how many extraterrestrial civilizations there will be in the universe, ” he said. “