Â鶹´«Ã½

I am 65. Assuming that I still weigh what I did at 25 (I wish!), what percentage of material from 40 years ago remains as part of me today?

Pat Sheil,

Sydney, Australia

In which direction in the sky did the big bang take place 13.8 billion years ago?

John Miller,

Ruthin, Denbighshire, UK

To answer this question – or ask a new one – visit newscientist.com/lastword. Terms and conditions apply.

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.