Early Monday morning, while the US East Coast was making coffee, dropping kids off at school, and cursing in traffic, a space rock as big as a 10-story building slipped past Earth.
It's between 50 and 111 feet (15 to 34 meters) long, and when it swung by Earth, 2017 AG3 was moving at 9.9 miles per second (16 kilometers per second). The near-Earth object, or NEO, came within about half the distance that the moon is from Earth, according to Slooh.
"This is moving very quickly, very nearby to us," Eric Feldman, an astronomer with Slooh, said during a live broadcast of the flyby at 7:47 a.m. ET on January 9. "It actually crosses the orbits of two planets, Venus and Earth."
A near miss
What would have happened if the asteroid had plowed into our atmosphere?
According to an asteroid-impact simulator called "Impact Earth!" by Purdue University, it might not have been as bad as it might sound.
Had a porous rock asteroid of 111 feet (34 meters) long hit Earth at a 45-degree angle, the simulator found, it would have exploded as an air burst. The blast would have released about 700 kilotons' worth of energy — dozens of times more powerful than the atomic bomb detonated over Hiroshima.
But since it would have occurred from a distance of about 10 miles high, it probably wouldn't have had much effect on the ground; if anything, a high-altitude boom may have sounded as loud as heavy traffic on the ground.