Â鶹´«Ã½

Why, when I see a rainbow, do I perceive two extra colours (yellowish and greenish) directly beneath violet? Am I seeing UV wavelengths, with my brain interpreting them as those colours?

Carlo Favetta,
Wyong, New South Wales, Australia

Why do we open our mouths when we put on mascara?
Megan Gill
London, 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 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.

Terms and conditions apply.