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 flash pattern (and colour) identify which lighthouse it is. The ship has a map that shows where lighthouses physically are. The ship also has a compass so it knows what direction it’s pointed and what bearing the lighthouse is. With all that information, you can put a line on the chart through the lighthouse and your ship must be on that line.
If you know how fast the ship is moving (which you should) and you can measure how fast the lighthouse’s bearing is changing, you now also know (approximately) how far you are from the lighthouse. The closer you are, the faster the lighthouse’s bearing will change.
Combine all that, and you know where you are. And, crucially, you know where the lighthouse is, which is a place you don’t want to be because the lighthouse is built on top of something that you should not snuggle your ship up to.
Latest Answers