Despite the impression one gets from textbooks, our current knowledge of the universe represents a small island in a vast ocean of ignorance. The scientific enterprise is all about expanding the landmass of this island. And it is fun to engage in the activity of gaining knowledge; knowing everything in advance would have been much more boring. Still, it would be shocking to learn all at once of the discoveries of an alien civilization that been doing scientific and technological exploration for billions of years, in contrast to our mere few centuries. The eminent science fiction writer Arthur C. Clarke codified this idea in the third of his three laws : “Any sufficiently advanced technology is indistinguishable from magic.” Put another way, members of such a civilization would appear to us as a pretty good approximation to God.

Meeting a piece of advanced technological equipment developed by an extraterrestrial intelligence might resemble an imaginary encounter of ancient cave people with a modern cell phone. At first, they would interpret it as a shiny rock, not recognizing it as a communication device. The same thing might have happened in reaction to the first detection of an interstellar visitor to the solar system, ‘Oumuamua, which showed six peculiar properties but was nevertheless interpreted as a rock by mainstream astronomers.

Because it would likely be relatively small, most advanced equipment could only be recognized in the darkness of space when it comes close enough to our nearest lamppost, the sun. We can search for technological “keys” under this lamppost, but most of them will stay unnoticed if they pass far away. More fundamentally, one may wonder whether we are able to recognize technologies that were not already developed by us. After all, these technologies might feature subtle purposes—like the cell phone communication signals that a cave person would miss.