Astronomers Adam Frank and Woodruff Sullivan of the Universities of Rochester and Washington University published an article in Astrobiolog magazine in May. They studied the question: "How often in the history of the universe has evolution led to the emergence of creatures with advanced technology?"
Frank, in an editorial for the New York Times published on June 10, concludes: "We do not know if advanced alien civilizations currently exist, but we have sufficient evidence that they existed in the history of space."
Astronomers came to this conclusion by reworking the famous Drake equation with fresh data. Astronomer Frank Drake compiled this equation in 1961 to calculate the likelihood of contact with extraterrestrial alien life.
Drake studied radio astronomy at Harvard and worked at NASA's Jet Propulsion Laboratory. He included in the equation the number of planets in each solar system suitable for the origin of intelligent life, and planets where there are conditions for life.
The development of telescopes has increased our knowledge of exoplanets (planets outside the solar system). In April, the Kepler spacecraft discovered 1,284 planets outside our solar system.
“Three of the seven quantities in Drake's equation are now known. We know how many stars are born each year. We know that almost 100% of stars have planets. And we know that 20-25% of these planets have conditions suitable for life. As a result, for the first time we can say something definite about extraterrestrial civilizations,”writes Adam Frank in the article.
To study the possibility of the existence of alien civilizations, Frank and Sullivan included time factors in the formula.
“As a result, we were left with only three unknowns, which we combined into one biotechnical probability: the possibility of the birth of life, the emergence of intelligent life and technical potential,” writes Frank. "The likelihood that we are not the first technologically advanced civilization is extremely high."
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In 2013, mathematicians at the University of Edinburgh claimed that aliens could send probes to Earth.
In the introduction to the study, published in the International Journal of Astrobiology, Arwen Nicholson and Duncan Forgana write, "We have concluded that a fleet of self-replicating probes is capable of rapidly exploring the galaxy and confirming the Fermi paradox."
The Fermi paradox suggests a high probability of the existence of extraterrestrial civilizations, despite the absence of their signs. According to Nicholson and Forgana, the likelihood of the existence of alien civilizations in the past is very high.
They were inspired by the Voyager 1 spacecraft, which in 40,000 years will reach the star AC + 79 3888. They assume that 40,000 years ago some extraterrestrial civilization sent a probe to our planet, and it could arrive at Earth at any time.
Drake equation N = R ⋅ fp ⋅ ne ⋅ fl ⋅ fi ⋅ fc ⋅ L
N = number of civilizations in the Milky Way that emit detectable radio-magnetic radiation
R * = level of star formation suitable for the development of intelligent life
fp = fraction of stars with planets
ne = number of planets in the solar system with conditions suitable for life
fl = fraction of planets suitable for origin of life
fi = fraction of habitable planets suitable for intelligent life
fc = fraction of civilizations that have created technologies that can send signals into space
L = lifetime of such a civilization