第三个地方：第一段里面 asteroids collide归为两类，在if if的里面，所以不是rubble piles，那就是...
Well, discovered in 2004, the asteroid quickly rose to the top of tables that measure the risk of so-calledpotentially hazardous asteroids (PHAs), or asteroids with widths of 460 feet (140 meters) or more that come within 20 lunar distances of Earth. Both the size of Apophis and how clos...
We called these orbits "quasi-stable orbits", in the sense that they do not collide with any of the primaries nor travel to large distances from them. From these orbits, it is possible to make better observations of the bodies in any scenario, and a more accurate estimation of their ...
gravity will change things so that when it comes back around again in 2036, it will collide with us.” The chance of Apophis passing through the keyhole, a 600-meter patch of space, is 1 in 5,500, based on current information. There is no shortage of ideas on how to deflect asteroid...
第三个地方：第一段里面 asteroids collide归为两类，在if if的里面，所以不是rubble piles，那就是...
小asteroid是monolithic， monolithic有快有慢。所以不能说他们都很快或者很慢。