From Ronald Baker, Colchester, Essex, UK
I don’t think the universe is infinite, but instead is in the form of the “surface” of a four-dimensional Euclidean hypersphere, so is finite. Nor do I think our universe is the only one: there may be other “bubbles” like ours in the wider cosmos, of which our universe is only one part. To say the universe is flat because nearby observations appear flat, so this therefore applies on a large scale too, is just as ridiculous as saying Earth must be flat because it looks like that on a small scale (29 June, p 31).
