This week’s new questions

Which is the most efficient swim stroke? And at what height do navigation compasses stop working?

1 June 2022

Young women swim breaststroke, wearing swimming caps and goggles. — Justa Jeskova/Getty Images

I am a casual swimmer who does a steady breaststroke in the pool. I am often overtaken by people doing front crawl, but who is actually swimming the more efficient stroke?

Cormac Byrne, London, UK

Close up of hand holding compass business navigate, passing through the crisis and growth in the economic.; Shutterstock ID 2115345185; purchase_order: -; job: -; client: -; other: - — Sataporn Sakda/Shutterstock

At what height do navigation compasses stop working?

Perry Bebbington, Kimberley, Nottinghamshire, 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.

New…