Â鶹´«Ã½

In a post-apocalyptic but non-nuclear world, how long would canned food remain edible?

Bob Gilbert,

Pender Island, British Columbia, Canada

Compared with a completely still universal reference point, how fast am I moving and in which direction?

Derek Johnson,

Moreton-in-Marsh, Gloucestershire, 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.

Â鶹´«Ã½ retains total editorial control…