How do scientists know that the “big bang” was not just a huge explosion in an existing universe, as opposed to an original event?

No scientist would claim to “know” (in a scientific sense) that there ever was a “big bang” — it is simply a theory to explain a number of observable phenomena.

Tony Baines, Bideford, Devon

The truth is that they don’t and some scientists set their stall by the “multiverse” theory — the idea that our Universe is just one of a number of existent universes, bringing into real science that science-fiction staple, the “parallel universe”. Other theories also suggest that our Universe is just the next in line of an infinite number of universes — a universe is created by a big bang-type event, expands then contracts, leading to another big-bang event, and so forth.

Sam Dodgin, Buckinghamshire

What is the origin of the phrase “without batting an eyelid”?

The “bat” in “to bat an eyelid” derives from the now obsolete word “bate”, in turn from the old French “batre” meaning “to beat the wings: to flutter”. The “bated”, as in “with bated breath”, also comes from this root and these two uses are about the only examples left in the English language.

Dr James Briggs, Westbury-on-Trym, Bristol

Postcodes are made up of two parts, eg E98 1TT, and in the second part of the code the letters C, I, K, M, O and V are never used. What is the reason for this?

The letters C, I, K, M, O and V are never used in the second (inward) part of the postcode to prevent confusion with G, 1 (or 7), R, N, 0 (or Q) and W in handwritten postcodes.

Ray Downing, Hon Secretary, Postal Mechanisation Study Circle

What is the origin of the letters around the dressage ring? They don’t seem to have any logic.