Scientists use quantum gravity to describe the universe before the Big Bang.Scientists may finally have an answer to a "big" question: If the Big Bang was the beginning of the universe, what could have caused it to happen? Using a theory called "loop quantum gravity," a group led by Penn State professor Abhay Ashtekar has shown that just before the Big Bang occurred, another universe very similar to ours may have been contracting. According to the group's findings, this previous universe eventually became so dense that a normally negligible repulsive component of the gravitational force overpowered the attractive component, causing...