End of the world by an asteroid impact

Here is a scientific eschatology. This is a cool simulation of what would happen to Earth if a 500 km asteroid collided with it. Of course, only Pink Floyd can provide the appropriate commentary on that. Here is the video (hat tip Open Culture) and some comments below that:



The simulation is fantastic. However, there are couple of things that need clarification. First, we are not in danger of running into a 500km asteroid. Such impacts happened early in the history of the solar system. In fact our Moon was formed when a Mars sized object collided with the Earth soon after the formation of the solar system, 4.5 billion years ago. Today, there is no such danger. Such large bodies either have already crashed into other bodies or are in a stable orbit around the Sun. The danger now comes from asteroids and comets that have diameters between 1 and 10 km. Of course, one of these was responsible for the demise of dinos, 65 million years ago.

Second, I'm not sure about their claim of Earth having been hit 6 times by 500km asteroids. As far as I know, there is no direct evidence for that. To the right is a plot that looks at the size and frequency of asteroid impacts (horizontal axis is size, and vertical axis is frequency). As expected, small impacts are more frequent than the large ones. The dino-killing impact (10km object) is identified as Chicxulub on the plot and it happens roughly once every 100 million years (see the bottom right part of the plot). My guess is that the makers of the video used this relation to estimate that collision with 500km objects must have happened roughly once every billion years. But, I think, it ignores the fact that such potential impactors have not been around since the early days of the solar system. By the way you can create your own asteroid scenario here and read about the consequences. I plugged in a 500 km object and it correctly stated that "Such impacts could only occur during the accumulation of the Earth, between 4.5 and 4 billion years ago". I gave my position 1000 km from the impact site and guess what? I was ejected into space: "Your position was inside the transient crater and ejected upon impact". Now this is so cool!! Some Pink Floyd please as I float into space.

So the take home lesson is: This is a very cool simulation of something that happened way in the past but is unlikely to happen in the future.