MEXICO CITY (Reuters) - Mexico's Teotihuacan, once the center of a sprawling pre-Hispanic empire, is set to become the launch pad for an attempt to communicate with extraterrestrial life. Starting on Tuesday, enthusiasts from around the world will have a chance to submit text, images, video and sounds that reflect human nature to be included in the message. Those contributions -- part of media company Yahoo's "Time Capsule" project -- will be digitalized and beamed with a laser into space on October 25 from the Pyramid of the Sun at Teotihuacan, now an archeological site near Mexico City. Archeologists say...