Here is a more technical explanation of the limit.
You send a radar signal out, then it bounces off of stuff and comes back at a frequency that depends on your relative motion to the thing it is bouncing back from. Given all of the stationary stuff around, there is a tremendous amount of signal coming back from "stationary stuff all around us", so the very first processing step is to put a filter that causes any signal corresponding to "stationary" to cancel itself out.
This lets you focus on things that are moving relative to the world around them. But makes seeing things that are standing still very hard.
Many animal brains play a similar trick. With the result that a dog can see you wave your hand a half-mile off. But if the treat is lying on the ground 5 feet away, it might as well be invisible.
You send a radar signal out, then it bounces off of stuff and comes back at a frequency that depends on your relative motion to the thing it is bouncing back from. Given all of the stationary stuff around, there is a tremendous amount of signal coming back from "stationary stuff all around us", so the very first processing step is to put a filter that causes any signal corresponding to "stationary" to cancel itself out.
This lets you focus on things that are moving relative to the world around them. But makes seeing things that are standing still very hard.
Many animal brains play a similar trick. With the result that a dog can see you wave your hand a half-mile off. But if the treat is lying on the ground 5 feet away, it might as well be invisible.