Chinese researchers have developed a table-top magnetic sensor that operates at room temperature and can spot magnetic signals a billion times fainter than the Earth’s own field. The Levitated Magnet Magnetometer (LeMaMa) functions like a compass with a needle that floats in mid-air with virtually no friction. By tracking the needle’s tiny deflections, the team can measure magnetic fields down to the femtotesla level – an advance that could widen the hunt for elusive dark matter particles or...