A weird quantum effect that was predicted decades ago has finally been demonstrated – if you make a cloud of gas cold and dense enough, you can make it invisible. Scientists at the Massachusetts Institute of Technology (MIT) used lasers to squeeze and cool lithium gas to densities and temperatures low enough that it scattered less light. If they can cool the cloud even closer to absolute zero (minus 459.67 degrees Fahrenheit, or minus 273.15 degrees Celsius), they say it will become completely invisible. The bizarre effect is the first ever specific example of a quantum mechanical process called Pauli...