The universe may be teeming with tiny alien microbes.
After all, scientists believe that such primitive life could exist on other planets in our solar system, in salty waters beneath their icy shells. Of course, we can’t be sure: microbes can’t send us messages (though we do plan to look for them).
But scientists are gaining a clearer understanding of why, out of the trillions of planets in the universe, far-flung intelligent civilizations haven’t called out to us — or even gotten a whiff of their presence. Scientific Reportsshow how difficult it would be for a planet to gradually evolve intelligent, communicative life: they argue that such a world would need both oceans and continents. and The surface must have been undergoing geological movement (called “plate tectonics”) for at least about 500 million years.
Taking into account other factors such as the percentage of habitable planets that host life and how long a civilization sending a signal would last, it seems unlikely that there could be many actively communicating civilizations in the universe.
“It’s like winning the lottery,” Taras Gheriya, a geophysicist at ETH Zurich in Switzerland and author of the study, told Mashable. “It’s so rare that the chances of contact are slim to none,” added Gheriya, who co-authored the study with geologist Robert Stern of the University of Texas at Dallas.
A NASA scientist saw the first Voyager images, and he was horrified by what he saw.
Estimates of the number of highly communicative civilizations in the galaxy vary widely, but are generally high. They all rely on a simple and elegant formula called the Drake Equation (see figure below). Developed by astronomer Frank Drake in 1961, the Drake Equation itself does not predict anything, but calculates an answer based on a few inputs. Recent proposals suggest that there must be at least 36 civilizations in the Milky Way. Drake estimates that there are about 10,000 civilizations scattered throughout the galaxy, which he calls vibrant, Star WarsAreas like this.
“It’s like winning the lottery.”
But the new study’s estimates are significantly lower.
“Only about four out of 10,000 galaxies have just one civilization,” Geriya said, “but it’s not impossible that there could be one or two civilizations per galaxy,” he added.
Certainly, our galaxy has at least one, but other galaxies may not be so lucky.
Artist’s impression of exoplanet Kepler-186f. Located 500 light-years from Earth, the planet orbits in the “habitable zone” of the solar system, where liquid water may exist.
Credit: NASA Ames / JPL-Caltech / T. Pyle
Rarity of alien civilizations
It’s not uncommon for experts to think that the number of communicative civilizations is small: Pascal Li, a senior planetary scientist at the SETI Institute, an organization that studies the origin and spread of life in the universe, believes the number of communicative, intelligent civilizations in our galaxy, which NASA estimates has between 100 billion and 400 billion stars (and many more planets), is roughly one.
“The possibility that we’re alone in the galaxy isn’t all that surprising,” Lee, who was not involved in the new study, told Mashable.
Mashable Lightspeed
Li and his research separately focused on a specific element of the Drake Equation and found that it dramatically reduces the likelihood of communication between civilizations.PhiSETI describes this percentage as the percentage of habitable planets on which intelligent life could emerge.
The Drake equation with the important variables is: Phi:
N = R∗ × fp × ne × fl × fi × fc × L
-
no = Number of civilizations that can communicate within the Milky Way Galaxy
-
R∗ = average rate of star formation in the Galaxy
-
debtp = fraction of stars with planets
-
yeahe = number of planets around each star with suitable environments for life
-
debtl = fraction of planets on which life originated
-
debti = Percentage of planets with intelligent or civilized life
-
debtc = Percentage of civilizations with technology that produces evidence of existence
-
and others = the average period of time a civilization leaves traces of its existence
A new study argues that Earth is special not just because it had relatively favorable conditions for temperate oceans to exist between the spreading continents. The outer parts of the planet were also working geologically for hundreds of millions of years, meaning that the tectonic plates that make up the planet’s crust were gradually shifting, shifting the continents and oceans. These conditions, the researchers say, encouraged the evolution of life and, ultimately, civilization.
However, they propose that these planetary factors occur together and constitute the proportion of planets on which civilizations develop.Phi) is probably extremely rare (for example, it’s probably rare for a planet to have the combination of material, size, and gravity required for plate tectonics to occur). Researchers estimate it’s in the range of 0.00003 to less than 0.002 percent of all planets. That means OptimisticIn fact, out of every 1,000 planets that could harbor life, two could develop civilizations.
A deep view of space captured by the James Webb Space Telescope. All objects except for the hexagram in the foreground are entire galaxies.
Credit: ESA Webb / NASA / CSA / A. Martel
Why are plate movements on Earth’s surface, such as the Pacific and North American plates, so important to the evolution of communicative civilizations? Imagine two planets with large continents and oceans: one with a billion years of plate tectonics, and one without. On a motionless planet, like Mars when it had oceans, the land masses don’t move. Everything is more or less stationary. “As a result, life either stays the way it is, or evolves very slowly,” Geriya explains. “Why would it need to evolve if it’s happy the way it is?”
But dramatic changes in continents and their coastlines, climate, etc., drive species to evolve. “That’s what plate tectonics does,” Geria emphasizes. “Plate tectonics always drives changes in complex species.” On Earth, the authors argue, modern plate tectonics “dramatically accelerated” the emergence of complex species during the Neoproterozoic Era (about 1 billion to 540 million years ago). “Species are driven to adapt or disperse,” Geria says. “It creates a very dynamic situation.”
Three billion years after microbes dominated the Earth, the first fossil records of animals appear during this time. The oceans teemed with life. The first dinosaurs appeared. Sharks, reptiles, insects, birds and mammals emerged.
“That’s plate tectonics at work. Plate tectonics is constantly driving change in complex species.”
This was the beginning of the long and uncertain road to civilization. We got there, but it wasn’t that long ago. Human civilization has only been around for about 5,500 years.
But the argument for long-lived tectonics is far from the only thing, or even the several things, that could have allowed rare intelligent life to eventually flower on Earth.
“The problem is, we don’t know what would trigger life to actually emerge and become intelligent,” SETI’s Lee said, highlighting a number of intriguing possibilities.
Saturn’s moon Enceladus erupts water ice, and the salty water beneath it could potentially support life.
Credit: NASA / JPL-Caltech / SSI
The giant asteroid that wiped out most of the dinosaurs (but not the birds!) may have helped humanity advance. In the aftermath of this catastrophe, mammals and burrowing animals came to dominate the surface, where dinosaurs were largely absent. “They became the apex predators on the surface, which eventually led to humans,” Lee points out. Some argue that the Moon, unusually large compared to Earth, created the balanced environment necessary for life to thrive. The Moon’s gravitational influence stabilized Earth’s chaotic rotation, preventing it from wobbling dramatically over time and causing climate chaos, as Mars does. Or perhaps it took so long for intelligent life to evolve on Earth because there was simply no life on Earth for hundreds of millions of years. There is no need for evolution Life will become smart enough to build interstellar spaceships and send signals through space.
“The dinosaurs didn’t need to invent the radio telescope or FM radio,” Lee said. (They lasted 165 million years. Humans have been around for about 300,000 years, and only invented the light bulb 145 years ago.)
“The dinosaurs didn’t need to invent the radio telescope or FM radio.”
Indeed, our world may be an exception. On average, there may only be one civilization in the galaxy at a time. Or maybe four per 10,000 galaxies, or somewhere in between. All we know for sure is that, for all its troubles and imperfections, there exists a communicable civilization on Earth. And that civilization has accomplished great things.
“The collapse of our civilization would be a huge loss for the universe,” Geriya said.
