Best Rated Facts
Chopping up onions activates a chemical reaction that releases sulfur gas. Water in the human eye reacts with sulfur gas to create sulfuric acid. Although the amount of acid is very small, it's enough to cause a burning sensation in the eye.
93 percent of all water on board the International Space Station is recycled. NASA has even installed a high tech water filter that turns urine into water. The US astronauts drink it, but the Russian astronauts refuse, although they don't mind handing over their urine to the Americans.