I’ve always been fascinated by astronomy’s variable sky community – the folks who look for things that change.

Most traditional astronomy involves parking a big telescope on a single object and watching it for a while. But the variable sky – things that change on time scales ranging from minutes to hours to days – is another world entirely, rich with unexplored possibility.

My latest effort in this area was a little riff over the weekend on the RAPTOR telescope at Los Alamos:

Looking for things that change is a simple concept. To understand our world, our brains do it all the time— tracking our field of vision, looking for things that are different from what they were a moment ago.

Something that moves might be prey— a rabbit we could eat. Or it might be a lion hoping to eat us. Either way, it pays to notice things in our field of view that change.

But astronomy has long been primarily about the study of the constant, eternally quiet sky. Most things don’t change most of the time. As a result, mammoth telescopes point for hours on end at tiny patches of sky, slowly tracking faint objects as they pass overhead, creating one or a handful of images of what is essentially an unchanging sky.

That is fine for studying a single object. But imagine hunting for rabbits or trying to avoid lions by looking at a single spot in the forest through a soda straw. You’d probably starve, unless you were eaten by a lion first.