In space, an asteroid that comes within 120,000 miles of Earth is considered a close call. So we should feel lucky that a flying boulder whizzed past us Sunday without incident, especially considering that scientists didn't see the massive rock coming until the last minute. The asteroid, named 2018 GE3, was the size of a football field, measuring about up to 361 feet in diameter. Because asteroids are relatively small and dark, LiveScience reports, it can be hard to predict when one will approach our planet — which is a fairly rare occurrence anyway.