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Rain? Or shine? Why do the apps get it wrong so often?Rob Watkins/Alamy If you hung out laundry, visited a beach or fired up the barbecue this week, you will almost certainly have consulted a weather app first. And you might not have been entirely happy with the results. Which raises the question: why are weather apps so rubbish? Even meteorologists like Rob Thompson at the University of Reading in the UK aren’t immune to these frustrations; he recently saw a dry night predicted and left his garden cushions out, only to find them soaked in the morning. It’s a classic example – when we complain about poor forecasts, it’s normally unexpected rain or snow we’re talking about. Our expectations – both of the apps and the weather – are a big part of the issue here. But that’...

An artist’s representation of the extreme engineMillen lab The hottest engine in the world is minuscule, reaches seemingly impossible efficiencies and could approximate nature’s tiniest machines. A thermodynamic engine is the simplest machine that can reveal how the laws of physics dictate the transformation of heat into useful work. It has a hot part and a cold part, which are connected by a “working fluid” that contracts and expands in cycles. Molly Message and James Millen at King’s College London and their colleagues built one of the most extreme engines ever by using a microscopic glass bead in place of the working fluid. They used an electric field to trap and levitate the bead in a small chamber made from metal and glass that was almost completely devoid of...