“For all we know, if galactic radiation-emitting civilizations exist, they could be located anywhere in the Milky Way. A signal reaching Earth could therefore be as old at 90,000 year. That is the time required for electromagnetic waves from our galaxy to travel the distance between Earth and the opposite end. If we add signals from other galaxies, this time span can become even longer. It is thus not unreasonable to think that, at the time we receive a signal, the emitting civilization no longer exist,” wrote Claudio Grimaldi, guest scientist at the Laboratory of Statistical Biophysics (LBS), Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland Send an email The Daily Galaxy.
“Not detecting any signals so far is not surprising,” added Grimaldi. “Even if we had perfect detectors scanning the entire sky, it would take more than 60% of the galaxy filled with signals for one of them to reach our planet on average.”
The Signals will come from the Civilization as It Was
“The signals will be from a civilization as it was,” said Frank DrakeThe famous Drake Equation was created by. “It is not a remote possibility — it is a high probability — that signals we receive will be from a “civilization that no longer exists.”
Most likely, alien signals will not reach Earth if they ever do. Claudio Grimaldi (physicist) and his collaborators calculated the area in the galaxy that should receive alien signals at any given time to update the 1961 Drake Equation.
“If the civilization emitted from the other side of the galaxy, when the signal arrives here, the civilization will already be gone,” says physicist Grimaldi.
Radio waves have been transmitted by humans for less than 80 years. This means that our radio waves only cover 0.001 percent the Milky Way.
Technologically savvy civilisations are born and die at an inexorable rate
The team, reported Science News and Mercury News, which included Frank Drake (now a professor emeritus at the SETI Institute in Mountain View, Calif., and the University of California, Santa Cruz), assumed technologically savvy civilizations are born and die at a constant rate. After a civilization ceases broadcasting, its ghostly signals continue to travel as concentric ripples across a pond.
Blue circles indicate that electromagnetic signals (blue circle) from alien civilisations will continue to travel through our Milky Way, even after they are gone. When a civilization is destroyed, a doughnut hole appears.
In March 2018, scientists gathered at Mountain View’s SETI Institute to discuss new ways to answer the question, “Are we alone?” The conference, titled “Decoding Alien Intelligence”, sought to broaden perspectives and expand the methodologies applied in the effort to detect extraterrestrial technology.
Decoding Alien Intelligence
“New tools are available that can enable this approach and help us decipher the evolutionary and probabilistic nature of advanced alien life,” said organizer and SETI Institute Director Nathalie Cabrol. “We can build a new roadmap that is multidisciplinary, that opens the toolbox.”
An update to the Drake Equation – a framework for discussing the probability of intelligent life existing beyond Earth – is receiving a fair bit of media buzz. The Drake equation was created during the beginning of modern SETI to provide a framework for scientists to discuss the possibility of extraterrestrial intelligent life. Frank Drake, a pioneer in the search of extraterrestrial intelligence and a participant in the new study, developed the probabilistic argument.
The study shows that signals travelling at the speed of light won’t reach us if advanced aliens exist far away from us. Any signals that do reach Earth will likely be the remains of an ancient civilization.
“There’s the chance that it’s still alive “but no longer transmitting,” Drake said. “Or it may have changed in a very big way, such as migrating from the planet to escape its expanding star.”
Message in a Bottle
Senior astronomer at the SETI Institute, Seth Shostak, still sees the value in collecting such a message: “To me, it is like finding a bottle on a beach with a note in it,” said Shostak. “It may be that whoever put the note in is long gone. But at least you know there’s somebody on the other side of the world.”
It’s important to remember that determining the longevity of a potential alien race based on the still-developing example of our own survival has a limited value, as SETI Institute’s Andrew Fraknoi Points out:
“Until we know more about our longevity, it is pure guesswork,” he said. “Every year we don’t destroy ourselves, we add one more year to what we know civilizations can do.”
If the civilization lasted less than 100,000 years — the time it takes light to cross the galaxy — then the odds of the signals reaching Earth while the civilization is still broadcasting are vanishingly small, the researchers reported. Radio waves have been transmitted by humans for less than 0.001 per cent of the Milky Way’s surface since 1980.
Avi ShporerResearch Scientist, MIT Kavli Institute for Astrophysics and Space Research via Claudio Grimaldi, SETI Institute Science News.
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Avi Shporer Research Scientist, MIT Kavli Institute for Astrophysics and Space Research. A Google ScholarAvi was previously a NASA Sagan Fellow at the Jet Propulsion Laboratory (JPL). His motto, not surprisingly, is a quote from Carl Sagan: “Somewhere, something incredible is waiting to be known.”
