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Albert Einstein may have been wrong about how mirrors work at the speed of light. Plus: how to extract gold from electronic waste.

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Mirror mystery

Over a century ago, Albert Einstein found a paradox during a thought experiment involving mirrors moving at the speed of light. Einstein’s calculations showed that light reflected from a mirror moving at the speed of light would have infinite intensity and amplitude. But Einstein’s special theory of relativity – the study of objects moving at the speed of light – suggested a different outcome: that any object moving at such high speed must turn transparent and reflect no light at all. Now a pair of physicists think they have now resolved this paradox. They say the problem is that Einstein’s idea of a mirror was unrealistically perfect. Read more

Whey to recycle

An aerogel made from old milk can extract highly pure gold nuggets from discarded computer motherboards. Discarded electronics, known as e-waste, often contain large amounts of gold and other heavy metals. Scientists have come up with methods to recover the valuable metals, but these processes often rely on synthetic chemicals that can damage the environment. Raffaele Mezzenga at ETH Zurich in Switzerland and his colleagues have developed a way to recover gold from e-waste by using a milk-derived aerogel, a type of gel where the liquid component is replaced with gas. “If you do an economic calculation, the margin is quite high because we start from a material [e-waste] which has no cost, and we start from a material [whey] which is very easy to process,” says Mezzenga. Read more

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Barry Webb/IGPOTY

The finalists in this year’s International Garden Photographer of the Year (IGPOTY) competition prove that stunning natural wonders are never too far away. Pictured above is Barry Webb’s composite shot of a trio of Cribraria slime moulds, found next to a decaying pine log in the forests of Buckinghamshire, UK, after weeks of searching. Webb’s initial motivation to simply take pictures of slime moulds has developed into an “obsessive quest” to document as many as possible, he says, “always striving to produce images that capture their otherworldly beauty”. Read more

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