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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

Does car tyre pressure affect the radius of the wheel, or the speedometer or milometer (odometer) readings?

Bryn Glover,

Kirkby Malzeard, North Yorkshire, UK

Would the Amazon turning to savannah significantly reduce the oxygen in our atmosphere?

Tony Lang, Stoneleigh, Surrey, UK

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

Questions should be…