The following submission statement was provided by /u/WallStreetDoesntBet:

If an alien were to look at Earth, many human technologies, from cell towers to fluorescent light bulbs, could be a beacon signifying the presence of life.

A technosignature (technomarker) is any measurable property or effect that provides scientific evidence of past or present technology. Technosignatures are analogous to biosignatures, which signal the presence of life, whether intelligent or not.

While scanning the sky for a TV broadcast of some extraterrestrial Olympics may sound straightforward, searching for signs of distant, advanced civilisations is a much more nuanced and difficult task than it might seem.

Please reply to OP's comment here: https://old.reddit.com/r/Futurology/comments/yb6m6d/signatures_of_alien_technology_could_be_how/iteynku/