Friday the 13th

Today is Friday the 13th. It is also a no moon phase - yep, 0% moon today.

Friday the 13th is considered to be a day of bad luck in many cultures. Countries that speak English, German, Polish, and Portuguese all have traditions involving bad luck on this date. So do those in parts of Greece and Spain. The fear of Friday the 13th stems from two separate fears -- the fear of the number 13 and the fear of Fridays. Both fears have deep roots in Western culture, most notably in Christian theology.

The fear of Friday the 13th is called paraskavedekatriaphobia.

January 13, 2006, and October 13, 2006, were not only Fridays, but the digits in the month, day, and year of each date add up to 13. This last occurred on October 13, 1520, and will next occur on May 13, 2011.

According to unverified legend (very likely untrue), the British Navy commissioned a ship in the 1800s called H.M.S. Friday, in order to quell the superstition. The navy selected the crew on a Friday, launched the ship on a Friday and even selected a man named James Friday as the ship's captain. Then, one Friday morning, the ship set off on its maiden voyage... and disappeared forever.

Some trace the infamy of the number 13 back to ancient Norse culture. In Norse mythology, the beloved hero Balder was killed at a banquet by the mischievous god Loki, who crashed the party of twelve, bringing the group to 13. This story, as well as the story of the Last Supper, led to one of the most entrenched 13-related beliefs: You should never sit down to a meal in a group of 13.

"It's been estimated that [U.S] $800 or $900 million is lost in business on this day because people will not fly or do business they would normally do," said Donald Dossey, founder of the Stress Management Center and Phobia Institute in Asheville, North Carolina.

More than 80 percent of high-rises lack a 13th floor. Many airports skip the 13th gate. Hospitals and hotels regularly have no room number 13.

On streets in Florence, Italy, the house between number 12 and 14 is addressed as 12 and a half.

Have a happy Friday the 13th! Hopefully bad luck will not occur for any of us, but rather good luck.