What Darkened the Sky on the Day of Christ's Crucifixion?

Immediately before the crucifixion of Jesus Christ, the Bible states, "Now from the sixth hour there was darkness over all the land until the ninth hour" (Matthew 27:45 ESV). That same account is also identified in Mark 15:33 and Luke 23:44. Yet the Bible does not state what caused the sky to darken. Could it have been the moon, excessive darkness, or something else?

In an article published by Answers.com, I provide what I believe is the correct understanding of that passage. You may see that at: http://christianity.answers.com/jesus/what-darkened-the-sky-on-the-day-of-christs-crucifixion.