An example that a relatively large space rock can approach the Earth suddenly started with what appeared as a bright star moving across the images that I had just obtained with the Catalina Sky Survey's 60 inch telescope on Mt. Lemmon, Arizona. It was about 100 times brighter than most of Earth approaching objects asteroid hunters discover. Over the next 64 hours it was tracked by 45 different observatories around the globe. This previously unknown space rock, now named 2017 AG5, is approximately 370 feet in diameter and can come closer than the Moon's distance to us.