My Article on Technosignatures

I also have a feature article in this month's issue of Physics World magazine, on technosignatures:

“Scanning the cosmos for signs of technology,” Physics World, October 2021, pp 32-36.

At the moment it's only available to registered users of the site, but registration is free. In a week or so there'll be a publicly available link and I'll post that then. 

"Technosignatures" are any sign of technology on another planet. Examining the "technosphere" is a burgeoning field that astronomers and astrophysicists are starting to think about, especially as the James Webb Space Telescope is about to launch (December, they say now) and as even better telescopes might come online next decade if recommended by the forthcoming NASA Decadal Survey. 

For the last two decades astronomers and astrobiologists have been thinking about how they might detect life on exoplanets, via "biosignatures." These might be the detection of methane in a planet's light spectrum, large amounts of oxygen, and a host of other possibilities, due to microbes or plant life. If life is ever detected on another planet, it's likely it will be via some type of biosignature -- it could happen in the next couple of decades.

Just in the last couple of years scientists have also begun thinking about "technosignatures," signs of technology akin to how biosignatures are signs of life. If other planets have an advanced technological civilization, akin to ours or more advanced (since ours is rather nascent), there may be signs we can detect astronomically. These might be city lights on their nightside, industrial pollution in their atmosphere, solar panels on their surface or in orbit, or megastructures like a Dyson sphere* or swarm or ring, or who knows what. People are making calculations of what might be detectable by the Webb telescope or TESS, and by telescopes that are hopefully recommended like LUVOIR and HabEx. There will be an enormous amount of data to sift through, looking for anomalies. I tried to cover some of this rapidly expanding field in my artice. 

* As you may know, a Dyson sphere is a hypothetical structure that would completely surround a star, thereby capturing all of its energy output. (Such an structure around our Sun, at Earth's distance, would capture 2 billion times as much solar energy as falls atop Earth's atmosphere.) Except a Dyson sphere isn't mechanically stable -- they would likely break up due to any drift, as Dyson wrote about in 1960 when he first proposed this idea. (A Star Trek: The Next Generation features a Dyson sphere. [Video] Magically it was stable.) If it could exist, a Dyson sphere would heat up and radiate outwards. A Dyson sphere at Earth's orbital distance would radiate at Earth's brightness temperature, 255 K, so with a blackbody spectrum with a peak wavelength of about 10 microns, in the infrared. People have actually done searches for Dyson spheres in the galaxy. 

Instead, a civilization might construct a more stable Dyson configuration like a swarm or ring or bubble -- I've used the figure from my article below. Why? One idea is to capture solar energy on them and beam microwaves to the planet's surface. But who knows what an advanced civilization might do with them -- maybe live on them! These should have a radiative signature too, a technosignature. It's all hypothetical of course, but fun to think about.... It was a fun article to write.