This week’s new questions

If a cyclist and runner exercise together, who is expending more energy? And if humans colonised Mars, would they calculate time based on the length of a Martian day or one on Earth?

17 May 2023

2AFPK7B Cyclist and Runner on Trail — Darryl Brooks/Alamy

I have just seen two people exercising together. She was running while he cycled beside her. She was only moving herself, but he was moving the bike too. Who expended more effort?

John Packham,

London, UK

This mosaic of Mars is a compilation of images captured by the Viking Orbiter 1. The center of the scene shows the entire Valles Marineris canyon system, more than 2,000 miles (3,000 kilometers) long, 370 miles (600 kilometers) wide and 5 miles (8 kilometers) deep, extending from Noctis Labyrinthus, the arcuate system of graben to the west, to the chaotic terrain to the east. — NASA/JPL-Caltech

If humans colonised Mars, how would they calculate time, as a Martian day is longer than one on Earth?

James Wilkins,

Southampton, UK

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