Have you ever looked at something on the horizon and it’s all shimmery and wavy and won’t hold still? That’s because air (and moisture in the air) diffracts light. And the air is not still, either. When you’re looking an incredibly small object that’s extremely far away the effect is rather like trying to see through one of those pebble textured glass shower doors, except if it were moving and the object you were looking at were the size of a gnat. And also several miles past the door.
Have you ever looked at something on the horizon and it’s all shimmery and wavy and won’t hold still? That’s because air (and moisture in the air) diffracts light. And the air is not still, either. When you’re looking an incredibly small object that’s extremely far away the effect is rather like trying to see through one of those pebble textured glass shower doors, except if it were moving and the object you were looking at were the size of a gnat. And also several miles past the door.