Shutterstock/Duncan Andison
Cycling on hilly roads, what is the best option to save energy: go as fast as possible downhill to gain momentum for the next climb, or stop pedalling to have a rest and regain some strength?
Jean-Luc Kerdelhué,
Nantes, France
Andrey Sarapulov/Alamy
Is it feasible to start a fire with a fart and a static spark from human hair?
Jed Stephens,
via email
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