#Space #Astronomy #Alien #Technosigniture
The truth is our there, if you know what you’re looking for…
In the search for extraterrestrial intelligence (SETI), we can’t simply point our telescopes out to the cosmos and hope to stumble across an alien civilisation. We need to know exactly what we’re looking for. The good news is that just as astrobiologists have a catalogue of tell-tale signs of life on other planets called biosignatures, SETI researchers have their own list of things that would indicate the existence of intelligent life beyond Earth. These are known as “technosignatures”.
SETI began in earnest in 1960 with Project Ozma, when Frank Drake used the Green Bank Telescope in West Virginia to search for artificial radio signals around two stars. The idea was that any alien transmissions would be identifiable because, like ours, they would look different to natural sources of radio waves. Since then, most searches have focussed on radio signals. And although most sightings have proved red herrings, including the famous Wow! Signal, this strategy is still throwing up some of the most promising candidates.
Around the same time as astronomers began scouring stars for radio signals, the physicist Freeman Dyson suggested another potential technosignature. Dyson reasoned that to satisfy its ever-increasing energy needs, an advanced alien civilisation would build an enormous solar power plant around its host star. This would heat up and generate an infrared glow in excess of what you would expect from an unadorned star – a glow that we could see from Earth.https://2c088916de0eb4f6fde39cec0c70e5f0.safeframe.googlesyndication.com/safeframe/1-0-38/html/container.html
These hypothetical megastructures are now known as Dyson spheres. Searching for them remains a minority sport, but some researchers have recently begun to step up the hunt by figuring out how to distinguish a genuine Dyson sphere from a star shrouded in dust.
Any advanced extraterrestrial civilisation is likely to have transformed its host planet with industry. SETI researchers have proposed that we could look for their non-natural waste products such as chlorofluorocarbons (CFCs), which can persist in the atmosphere for tens of thousands of years. Astrophysicist Avi Loeb of Harvard University has also suggested light pollution on the night side of an extrasolar planet as a possible sign of technological civilizations.
If intelligent aliens are, like us, curious about the fundamental forces of nature, they might have built a particle collider that makes our Large Hadron Collider look puny. An accelerator powered by a black hole, for instance, would produce super-high-energy neutrinos, particles that could be detected from Earth.
Any advanced civilisation runs the risk of destroying itself, and the fallout might be visible to distant observers. Nuclear bombs would release flashes of gamma rays, but they would be fleeting and the resulting dust would be hard to distinguish from that produced by an asteroid strike.