why do they do that
In: Earth Science
There wasn’t always GPS and satellites to guide boats. Without a lighthouse a ship could crash into the shore which would be bad for a number of reasons. The reason the light rotates is a boat can be coming from several directions and it allows all potential boats to be safe.
Another point – the only reason a lighthouse would spin, these days, is because it is a historical artifact. A modern lighthouse just uses a powerful light, that flashes and shines all around. Various filament light sources, like tungsten and halogen, as well as xenon flash tubes have been used, but these days LED light sources have largely taken over.
1. The purpose of a lighthouse is to beacon.
2. Typically you want beacon signals to travel as far as possible.
3. It costs a lot of energy to light up the entire sky. It’s much easier to brighten a small part of it, and turn it.
4. It’s also more noticeable at distance to have a blinking light.
As well as making it clear what’s a lighthouse and what’s just a normal light, but by introducing the rotating lens system you can do other things with the light such as making it appear to flash at different speeds, or even different colours.
By doing this, you can help mariners figure out just which lighthouse they’re looking at. To take two local lighthouses from my area, one of them flashes a red light for one second, then off for four seconds, and then repeats the cycle.
Another lighthouse further up the coast gives three white flashes even ten seconds.
By having these characteristics marked on charts, mariners are able to tell where on the coast they are at night. It’s less important nowadays that modern electronic navigation aids are available, but in years gone by it was invaluable.
Each lighthouse turns at a different rate by noting how long between the flashes you can tell which light house you are passing and so where you are and what the nature of the hazard is.
A lighthouse does not actually have a very bright light on them. Early lighthouses might have been powered by candles, later improved with oil lamps. But even today some lighthouses are battery powered and have to conserve their power which limits the power of the light. The trick with a lighthouse and why they are able to get a tiny light to be so visible is that they have a big lense and reflectors which focus all the light in one single direction. This can make even the tiny amount of light from a candle visible for miles. The issue is that doing this makes the light invisible from all other angles. So a lighthouse have to constantly move the lens around to focus the light at different parts of the ocean so that all the ships will be able to see it. From a ships perspective a lighthouse looks like it is blinking. This also have several adavantages. Different lighthouses have different patterns of lights and different speeds so it is possible to identify a lighthouse just by looking at its light. It is also possible to set up the lights to help sailors find out where they are. So this feature have been retained even with more modern lighthouses.
So ships can see that there is land there from really far away in the night, the beam is tight and focused, making it brighter, but they have to spin it so it’s visible all around
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