Is it possible to run along the top of a moving train?
Unless you're starring in a real-life action film, you'd have trouble keeping up with a speeding train without being swept away.
Asked by: Alan Blackwood, by email
Anyone who’s seen a film like Butch Cassidy and the Sundance Kid, which features a character running along a train roof, will know it’s possible – as long as the train isn’t moving too fast. As speed picks up, the air blowing over the carriages becomes stronger, along with their rattle and roll, and running becomes all but impossible.
Robert is a science writer and visiting professor of science at Aston University.