Free Astronomy Magazine July-August 2021

JULY-AUGUST 2021 T echnosignatures are observational manifestations of technology, particu- larly those that could be detected with the tools of astronomy. City lights, air pollution, and satellites are all examples of technosignatures on Earth. Could the next generation of telescopes find evidence of alien technology on another planet? [TechnoClimes 2020] M egastructures such as Clarke's belts (populous swarms of satellites, an example above) or Dyson spheres (cages to imprison stellar heat) would reduce the brightness of planets and stars, pro- ducing an excess infrared, phenom- ena recognizable from Earth. [TechnoClimes 2020] which defines the relative value of a hypothetical alien technosigna- ture with respect to its terrestrial ex- pression. To better understand this concept, let’s assume that an alien civilization has built a giant space station around its planet. In this spe- cific case, the value of the ichno- scale would be equal to the average size of that megastructure divided by the average size of the Interna- tional Space Station, the largest ar- tifact currently present in Earth’s orbit. Considering the small size of the ISS, it is understandable that the ichnoscale would be of some order of magnitude. As a second example, let’s imagine we sight an alien probe passing through our solar sys- tem. In this case the ichnoscale would not be much bigger than one, since we too are theoretically able to send a probe to a nearby planetary system, as evidenced by not yet available, or the construc- tion of very large or very bright structures, works that would hardly be a top priority. It is also for this reason that many insiders believe that our first contact is more likely to take place with a more advanced civilization than ours. “More or less advanced” is an ex- pression often used when talking about a possible alien civilization. In reality, it has a very relative mean- ing, because we have only one ex- perience and no idea how techno- logically more or less advanced oth- ers may be. TechnoClimes 2020 has provided a tool that allows for a less subjective assessment. It is an arbi- trary but reasonable scale that uses the relative weight of each terres- trial technosignature as a unit of measurement. Technosignatures are quantified through a parameter called “ichnoscale” (footprint scale),