Adriatic oil, gas exploration raises concerns for Croatia tourism Empty tables, crowded gyms: Learning with Density Smart gadgets from guns to cars ripe for hacking For Rio's Olympic sailors, it's not safe to go in the water Hitchhiking robot's cross-country trip in US ends in Philly Obama to unveil 'biggest step ever' in climate fight Tracking the retreat of Arctic ice Challenger, Columbia wreckage on public display for 1st time Cecil the lion lights up New York's Empire State building Another US hunter suspected of illegal Zimbabwe lion kill China tightens controls on export of drones, supercomputers Astronaut mementoes: Cowboy boots, prayer beads, lunch box Bend me, shape me, any way you want me: Scientists curve nanoparticle sheets into complex forms "Mystery booms" cause identified Affordable genetic diagnostic technique for target DNA analysis developed Innovations from the wild world of optics and photonics Ethylene production via sunlight opens door to future Computing at full capacity Social media amplifies damage of product recalls to firms—rivals, too Shedding light on millipede evolution