Light is faster than anything else in the known universe, though its speed can change depending on what it's passing through.
A mysterious epidemic that began in the Mediterranean at the start of the year looks set to wipe out all of the Mediterranean and Red Sea’s urchins, and possibly their coral reefs too.
A bunker discovered near the city of Anda in northeast China is believed to be the largest test site of Imperial Japan's infamous Unit 731, which conducted horrifying human experiments during the 1940s.
Challenger by name, challenging by nature.