If you’ve ever played the game where you burn an ant with a magnifying glass or have ever reflected sunlight from your watch face into someone’s eye, then you’re already familiar with the concept of heliostats.

Even though both those examples are a bit unpleasant (maybe even sadistic?), they illustrate the concept of redirecting and focusing sunlight where we want it when we want it. The same is true for heliostatic lighting systems.

As this article explains, heliostats are mirrors mounted on buildings that track sunlight and redirect it where light is needed. Sometimes, the mirrors redirect sunlight to other mirrors, which then get it where it needs to go.

Another interesting use is combining the mirrors — which don’t concentrate sunlight and so there is no fire hazard — with fiber optics. This allows the redirected sunlight to penetrate deep into buildings, even basements.

Does this mean that eventually, buildings might be totally artificial light-free during the day? I’m not sure it could ever come to that, but it is an interesting way to harvest daylight and potentially save on energy costs.