Signals of Extinct Extraterrestrial Civilizations –“Echo Throughout the Milky Way”

 

“For all we know, if galactic radiation-emitting civilizations exist, they could be located anywhere in the Milky Way. A signal reaching Earth could thus be as old as about 90,000 years, that is the time it takes for electromagnetic waves to cover the distance between us and the opposite edge of our galaxy, and this time span becomes even larger if we take into account signals from other galaxies. 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 in an email to 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 oin average.”

The Signals Will be from a Civilization as It Was

“The signals will be from a civilization as it was,” said Frank Drake, creator of the famous Drake Equation. “It is not a remote possibility — it is a high probability — that signals we receive will be from a “civilization that no longer exists.”

If signals from an alien civilization ever reach Earth, odds are the aliens will already be dead. In an effort to update the 1961 Drake Equation, which estimates the number of detectable, intelligent civilizations in the Milky Way, physicist Claudio Grimaldi and colleagues calculated the area of the galaxy that should be filled with alien signals at a given point in time.

“If the civilization emitted from the other side of the galaxy, when the signal arrives here, the civilization will already be gone,” says physicist Grimald.

Technologically Savvy Civilizations are Born and Die at a Constant 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. When a civilization dies out and stops broadcasting, the ghostly signals it had sent continue traveling like concentric ripples on a pond.

Electromagnetic signals (blue circles) from alien civilizations shown in the image above will continue traveling through the Milky Way even after the aliens are gone. The appearance of a doughnut hole represents when a civilization dies out.

Scientists gathered at the SETI Institute in Mountain View, California in March, 2018 to chart new approaches to answering 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.”

A recently released 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 developed during the outset of the modern SETI field to act as a framework for the scientific community to discuss the probability of advanced extraterrestrial life. The probabilistic argument was devised by pioneer in the search for extraterrestrial intelligence, Dr. Frank Drake, who participated in the new study.

According to the study, if advanced aliens exist on the furthest edge of the galaxy from us, any signals traveling at the speed of light will not reach us for quite some time. Any signals that do reach our planet will likely be vestiges of a long dead 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.”

The Aliens Before Us –“We are Not the First Technological Civilization” (Or, are We?)

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. Humans, for example, have been transmitting radio waves for only about 80 years, so our radio waves cover less than 0.001 percent of the Milky Way. 

The Daily Galaxy, Avi Shporer, Research Scientist, MIT Kavli Institute for Astrophysics and Space Research via Claudio Grimaldi,   SETI Institute and Science News. Avi was formerly a NASA Sagan Fellow at the Jet Propulsion Laboratory (JPL).

 

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