On 21 June, the Chinese Academy of Sciences hailed a breakthrough – a major upgrade to a kind of quantum device that measures magnetic fields. The announcement vanished after a journalist pointed out the invention’s potential military implications: it could help China lock down the South China Sea.
“I was surprised by the removal,” says Stephen Chen of the South China Morning Post, who raised the issue. “I have been covering Chinese science for many years, and it is rare.”
Magnetometers have been used to detect submarines since the second world war. They are able to do this because they can measure an anomaly in Earth’s magnetic field – like one caused by a massive hunk of metal.
But today’s devices can only detect a submarine at fairly short range, so tend to be used to home in on the location once the sub has already been spotted on sonar.