NATIONAL GEOGRAPHIC: A large meteor blazed across the midwestern U.S. sky Wednesday night. Igniting over Wisconsin, Iowa, Illinois, and Missouri around 10:15 p.m., local time, the fireball briefly turned night to green-tinged day and unleashed a sonic boom heard for hundreds of miles around. Based on video of the fireball, astronomer Mark Hammergren thinks the meteoroid—the space rock that causes the meteor, or fireball—may have been up to six feet (1.8 meters) wide and weighed roughly a thousand pounds (453 kilograms) or more. MORE RELATED: A hundred years after a mysterious and massive explosion struck Russia, experts are warning that […]