The Range Lights Still in Service
Most navigational aids have been quietly retired. Range lights have not, and the reason is that they solve a problem satellite positioning does not quite solve.
Why the Back Light Is Always Taller
The height difference between the two towers is not aesthetic and it is not arbitrary. It is the single number that decides how precise the range is.
How Two Lights Make a Line
A single lighthouse tells you where something is. Two lights, correctly placed, tell you where you are, which is a much harder problem and a much older one.