Professor Bill Kreiger, shown with an orrery model solar system in his York College classroom Thursday, assures us "the world will not end because of
Professor Bill Kreiger, shown with an orrery model solar system in his York College classroom Thursday, assures us "the world will not end because of a calendar date and a full moon." To see the model Earth's rotation in a video, visit www.yorkdispatch.com and click on the "check out our YouTube page" link. (Randy Flaum — rflaum@yorkdispatch.com)

For the most superstitious among us, Friday offers a double whammy.

The weekend begins as Friday the 13th collides with a full moon — the first time since Oct. 13, 2000.

The day may rouse phobias and paranoia, but there's no science to prove Friday the 13th and a full moon are more ominous than any other day.

"Man has superstitions and always will. But, really, it's just nature. The world will not end because of a calendar date and full moon," said Bill Kreiger, professor of earth sciences and science education at York College.

Fear of Friday the 13th stems from a fear of the number 13, he said.

"It goes back to biblical times and the 13th disciple," Kreiger said, referring to the Bible story in which Judas Iscariot betrayed Jesus Christ.

Since then, 13 and Friday the 13th have been considered an unlucky number and day, he said.

"It's related to religion and social behavior, not science," Kreiger said.

Friday's other half: As for the full moon, folklore would have us believe that spot in the lunar cycle affects fertility, sleep quality, human behavior and politics.

"But there's no scientific evidence the moon is responsible for that," he said.

However, the moon can stir up the oceans.

If you're going to the beach this weekend, you might find bigger waves. The gravitational force of the moon's position to Earth will create high tide.

"The moon does control tides, but it doesn't control us," Kreiger said.

Yet many cultures have feared otherwise. Some ancient civilizations believed the full moon was a way to stop their armies from moving at night, he said.

"These fears aren't based in science. In science we have to be able to observe, experiment and get facts and figures," he said.

This Friday the 13th is the only one of the year, and that might be a salve for some apprehensive Yorkers.

But there are three in 2015: Feb. 13, March 13 and Nov. 13.

None of those dates will fall on a full moon.

After this week, a Friday the 13th and full moon won't happen together until Oct. 13, 2049.

So that means we have at least 35 years until something bad happens, right?