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.
Just to add to this, air at different temperatures and moisture levels bends light to different degrees, which is why the layers and pockets of air that form our atmosphere make stars shimmer. It’s partially why astronomers are so eager to get telescopes into space (like Hubble and the James Webb), since the lack of this effect lets them resolve much smaller light sources than you could hope to beneath the atmosphere.
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.
Just to add to this, air at different temperatures and moisture levels bends light to different degrees, which is why the layers and pockets of air that form our atmosphere make stars shimmer. It’s partially why astronomers are so eager to get telescopes into space (like Hubble and the James Webb), since the lack of this effect lets them resolve much smaller light sources than you could hope to beneath the atmosphere.