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 Earth is ill prepared to face a cosmic catastrophe that could do similar damage. The blast, known as the Tunguska event, leveled some 770 square miles (2,000 square kilometers) of forest with the power of nearly 200 Hiroshima-size atomic bombs. Remarkably few people witnessed the event, and debate has raged for decades about its cause. One of the leading theories is that a comet or asteroid hit Earth or exploded upon entering the atmosphere above remote western Siberia. “Had that same object exploded over a metropolitan area, there would have been millions of people killed,” U.S. Representative Dana Rohrabacher (a Republican from California) said yesterday at a briefing at the Planetary Society in Pasadena, California. MORE