The argument – that an alien species would interact with the universe in ways that we would not think to look for – kind of falls down on its face with the hypothetical. A sentient ant colony would notice right away that large sections of their observed universe would contain a near-infinite number of objects and activities that were not explainable as natural phenomena but could be explained as the result of conscious, artificial action: the buildings alone would give the game away. It’d be like us working on SETI and not noticing that Alpha Centauri happened to have a Dyson sphere.
At least, that’s my first take. No doubt people will pop by to tell me why I’m wrong.
I disagree. My only example would be Ender’s Game. The whole war between Humans and Formics was a complete ignorance of what sentience means to both races and how to communicate with each other. As for the Ants in XKCD, pheromones may be a sign to them of sentience and communication. Ants also build tunnels in the ground and so their idea of artificial contructs will also be different.
Erm, if there are Dyson spheres nearby, galactically, we most likely wouldn’t be able to see them as they’d be blocking the energy output. But other than that, yeah.
I’ve seen people pose all sorts of arguments that some of the things in the observable universe could not have been produced by natural phenomena and must therefore have been created by an intelligence, and they haven’t gained much traction among scientists either. Then again…