Â鶹´«Ã½

Gravitational waves arise when very heavy objects spiral into each other, but is there a lower limit to this? Do I create one when I crash into the sofa after a day of work?

Bruno Billiaert, Duffel, Belgium

Limb renewal Why can’t humans regrow limbs like an axolotl or a lizard?

Fabiola Bartolomei, Moscow, Russia

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.

Â鶹´«Ã½ retains total editorial control over the published content and reserves all rights to reuse question and answer material that has been submitted by readers in any medium or in any format.

You can also submit answers by post to: The Last Word, Â鶹´«Ã½, 25 Bedford Street, London WC2E 9ES.

Terms and conditions apply.