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.
We are two astronomers who work on the search for extraterrestrial intelligence — or SETI. In our research, we try to characterize and detect signs of technology originating from beyond Earth. These are called technosignatures. While scanning the sky for a TV broadcast of some extraterrestrial Olympics may sound straightforward, searching for signs of distant, advanced civilizations is a much more nuanced and difficult task than it might seem.
