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Last Word is Â鶹´«Ã½â€™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
I use a petrol lawn mower – does it emit more carbon than the grass captures?
Hugh Meteyard,
Theydon Bois, Essex, UK
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Heat a ceramic mug of water in the microwave, tap it with a steel spoon, and the pitch is higher than before it went in. Why?
Francis Westfield,
Stoke-on-Trent, Staffordshire, UK
To answer this question – or ask a new one – email lastword@newscientist.com.
Questions should be scientific enquiries about everyday phenomena, and both questions and answers should be concise. We reserve the right to edit items for clarity and style. Please include a postal address, daytime telephone number and email address.
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