This passage from John Pierce, An Introduction to Information Theory:

"also note that while Euclidean geometry is a mathematical theory which serves surveyors and navigators admirably in their practical concerns, there is reason to believe that Euclidean geometry is not quite accurate in describing astronomical phenomena"

got me wondering. What makes Euclidean geometry inaccurate for this purpose?

The book is neither about geometry, nor about astronomy, so this issue remains unexplained.