From Alan Hewer, Seaford, East Sussex, UK
I see that researchers have dismissed the likelihood of an advanced civilisation on planet K2-18b because no radio waves have been detected. This seems to be a narrow-minded approach. The earliest known civilisation on Earth was that of the Sumerians over 5000 years ago, and we can hardly call the ancient Egyptians and Greeks uncivilised. Radio waves, however, were first produced only some 140 years ago, and so can hardly be considered a sign of civilisation. It seems a little premature to consider these to be the last word in communication methods (28 February, p 11). In 1000 years’ time, who knows what we’ll be using?
