Lab notes: could Einstein have been wrong about the speed of light?

It's a controversial idea, but a new paper this week describes for first time how scientists can test the controversial idea that the speed of light is not a constant. If the theory is proven, it would overturn Einstein's century-old claim that the speed of light is a constant. It could change the way we view the cosmos, but until it's proven (or not) we can content ourselves with what we do know - and for some of that we have the Saturn-orbiting Cassini spacecraft to thank. After nearly two decades, more than 300,000 incredible images and the discovery of no fewer than seven moons, Cassini is about to begin its swansong, which will end when the craft finally dives into Saturn itself on 15 September. If the noble end of this plucky little orbiter brings you down, why not cheer up with a little festive "neural karaoke"? An AI project from the University of Toronto can take any digital photo and transform it into a computer-generated singalong - and we have their Christmas effort for you to enjoy. Other cheering news is that a single dose of psilocybin, the active ingredient of magic mushrooms, can lift anxiety and depression experienced by people with advanced cancer for six months or even longer, according to two new studies. An even happier note sounded this week for women who are in danger of passing on devastating and often fatal mitochondiral disorders to their children - UK doctors are poised to seek permission this month to create Britain's first baby from the DNA of three people if the government's fertility regulator approves the treatment.