Each month a new planet is discovered that bears similarities to our own - and it is becoming increasingly apparent Earth is not unique.
So it stands to reason that of the billions of Earth-like planets in our galaxy alone, there might be another that hosts life.
It’s a thought that is gaining more credence all the time, and now Nasa has released a fascinating book detailing how, or if, we might communicate with some of these worlds.
Some of the most interesting chapters tackle the issue of alien communication in the past, present and future.
In one section, for example, William Edmondson from the University of Birmingham considers the possibility that rock art on Earth is of extraterrestrial origin.
‘We can say little, if anything, about what these patterns signify, why they were cut into rocks, or who created them,’ he writes.
‘For all intents and purposes, they might have been made by aliens.’
The book is titled Archaeology, Anthropology and Interstellar Communication.
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