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Last Word is New ������ý’s long-running series in which readers give scientific answers to each other’s questions, ranging from the minutiae of everyday life to absurd astronomical hypotheticals. To answer a question or ask a new one, email lastword@newscientist.com

Is short-sightedness found in other animals? Did it affect ancient humans too?

Simon Pearce

Bromley Cross, Lancashire, UK

Could a massive asteroid that hit Mars or the moon affect Earth? How big would it need to be, and what would happen?

John Rymell

London, UK

To answer this question – or ask a new one – email lastword@newscientist.com.

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