The good news is that the ozone hole over Antarctica is slowly healing, thanks to controls on ozone-depleting substances that were once widely used in products such as refrigerators and aerosol cans. Stratospheric ozone protects us from harmful ultraviolet radiation that can cause problems such as skin cancer and crop damage.

A metal that reacts with seawater to produce an electric field may help keep sharks at bay. But the idea isn't to protect humans from shark attacks. Just the opposite: scientists hope the metal will save sharks from senseless deaths in fishing nets.

An estimated 11 million to 13 million sharks die each year as "bycatch," collateral damage in the hunt for other fish. Sharks grow slowly and can take many years to reach reproductive age, so their populations are being severely impacted by fishing.