by Adam Frank April 2, 2018 (npr.org)
• Harvard astrophysicists Avi Loeb and Manasvi Lingam are exploring the universe looking for ‘exo-civilizations’ using “bio-signatures” and “techno-signatures” that are more technologically advanced than the radio waves that SETI depends on. Loeb and Lingam have explored a number of different ways we might find markers of another civilization.
• For instance, light reflected from a planet covered in power-generating solar cells would carry a techno-signature “signal” of all that silicon. Loeb was quick to point out that a civilization need not be alive now for us to find the techno-signatures that they left behind.
• As our technologies gets better we might suddenly find lots of signals from the activity of technological civilizations. Even a slight change in gravitational waves would create a techno-signature. There also may be artifacts existing in space rather than on planets. “These ‘messages in a bottle’ would be very difficult to detect because they would be putting out very low power,” Loeb said.
• “We humans are probably not special,” Loeb says. With so many planets in the universe, the rise of civilizations may not be so usual. And what makes this moment in history so unique is that we are now poised to start observing exo-planets and their environments in all kinds of new ways.
We’re entering uncharted territory.
For more than 2,000 years, we humans have been arguing about life and, in particular, intelligent life in the universe. But arguing was pretty much where it always ended.
For all that time, we never had any evidence or any data that could raise the discussion above two people with different opinions yelling at each other.
But this era may well be nearing its end.
The “exoplanet” revolution of the last 20 years has shown us that the universe is awash in alien worlds. More exciting, we now have methods where the atmospheres of those worlds may provide indirect evidence — called “bio-signatures” — for the existence of life.
Over the next few decades we may finally have data relevant to the question of other life in the universe.
But what if we want to ask about intelligence? What about alien civilizations — or, as I like to call them, “exo-civilizations”? This is something I have been thinking about a lot over the last few years (it’s the subject of my new book). In carrying out my own studies, I have often been drawn to the work of Harvard astrophysicist Avi Loeb.
Loeb works on a variety of subjects, including black holes and early cosmic history. But together with collaborator Manasvi Lingam, Loeb has carried out work that is simultaneously deep and expansive on the topic of astrobiology and exo-civilizations.
When we think of aliens and science, we usual usually think of the Search of Extraterrestrial Intelligence (SETI). This has often meant radio telescopes being used to search for messages purposely beamed at us from an exo-civilization. But unlike these kinds of purposeful signals, a “techno-signature” is an unintentional marker of the civilization’s existence. With the discovery of so many exo-planets, astronomers will now be spending a lot time staring at these other worlds in many different wavelengths of light (not just radio). This is how they hope to find bio-signatures.
But what about techno-signatures?
Loeb and Lingam have explored a number of different ways we might find markers of another civilization. What, for example, would be the consequences of a civilization covering large portions of its planet in solar cells to generate power? Lingam and Loeb have shown that light reflected from such a planet would carry a “signal” of all that silicon on the planet’s surface, making it an intriguing example of a techno-signature.
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