I keep reading that lighthouses help sailors 1) be aware of dangers like rocks and reefs, and 2) navigate in the dark. I understand that lighthouses beam a series of flashes that a sailor can see from far away, but I’m not quite sure how seeing a series of flashes in the dark from a single point-source can accomplish point 1 and point 2.
In: 8
The lighthouse itself is always built on the shore (or atop a reef), so the first rule is that a sailor never wants to get too close, or else they will risk running aground and either getting stuck, or sinking.
The lighthouse itself will sometimes be painted with a unique pattern of stripes or colors, so that in the daytime sailors can identify the lighthouse and then determine their location relative to the lighthouse with a compass. (There is a chart or some kind of book which lists lighthouse markings IIRC)
At night time, a series of glass lenses rotates around the light which causes it to “flash” when viewed from a distance. The speed that these lenses rotate will change the number of times per minute that the light appears to flash. So for example, one flash every 10 seconds = lighthouse #1, one flash every 5 seconds = lighthouse #2 or whatever. There will be a code written on marine charts (aka maps) which tells a sailor which flash pattern corresponds to which lighthouse.
Additionally, other marine navigation lights and marker bouys have coloured lights on them which can indicate hazards. These will flash with a pattern of green, red, yellow or white lights and can be decoded by using the marine chart.
Latest Answers