What is Visibility?
Visibility is, simply, the distance we can see at a particular time. It can greatly affect things we do particularly when we travel.

Mist and fog cause lots of car accidents every year, and can be difficult for drivers to predict as they can be very patchy, collecting in hollows. Pilots and sailors too have to be wary of fog despite the advanced use of radars to help them navigate.

How do we know how far we can see?
Visibility is sometimes quite hard to judge. The easiest way is to find points of reference at known distances. But some more sophisticated equipment can help us to be more specific.