The thoughts in our brains emit electromagnetic waves on all frequencies, including what is visible light to us. They can be displayed at a significant distance.
Oh! They are illiterate, which explains why their technological growth is linear rather than exponential.
I had a theory (proven wrong many times) that the culture in Star Wars was illiterate. It isn't. The technology in Star Wars is stagnant over millennia because it isn't a Science Fiction story.
Also, it sounds like there might be an "Invention Of Lying" theme here.
EDIT - I think my illiterate theory is falling apart again. They are writing on the irises... Some day I would like to see an illiterate, advanced civilization, but it sounds like it isn't going to be this book. No explanation yet as to why their progress is linear.
