Why Do Lighthouses Have Red Stripes?

since ancient times lighthouses are kept Mariners safe using some of the most cutting-edge technology available granted I'm not going to claim that a red and white stripy paint job is Cutting Edge technology but it's arguably just as important as things like the fresnel lens which is frequently referenced as the invention that saved a million ships the whole point of a lighthouse is to Mark a dangerous object or show the way to a port or Harbor the earliest ones were simply open fires burning on top of Hills but over time they evolved into platforms or even custom buildings on land they could be small structures that use the height of the surrounding Cliffs or Hills to ensure they had sufficient geographical range geographical ranges just the distance over which are able to observe something due to the curvature of the earth out at Sea of course you instead need to rely on the height of the building itself that all in the lighthouse the further away it can be seen and the more time that ships will have to take appropriate action the thing is Lighthouse Builders quickly found that rather than height the limiting factor governing visibility was actually the intensity of the light imagine a single point source of light it radiates energy out in all directions so any Observer is only going to see a tiny percentage of the overall energy of the original light as that Observer gets further away the energy that reaches them quickly diminishes you're never going to increase the observed brightness sufficiently by simply increasing the power of your light instead you need to focus the energy of the light in a single Direction one relatively simple solution is to surround the light with some sort of parabolic reflector any light that hits the parabola is reflected in such a way that it's focused in the same direction you can then simply rotate the parabola so that any light will be seen as a flashing light from all directions but we can go one step further all these beams in front of the light can be focused as well you just need a lens shaped correctly any light emitted from the focal point of the lens will be bent to bring it into what we call the focal plane of the light of course any light that isn't emitted from the focal point of the lens so stuff that's come from that Parabola will now be deflected away from the the focal plane but overall it's still better with the lens than without to make it even better still you just make the lens bigger but then we run into problems to increase the height of the lens you have to increase its depth and this would make it prohibitively difficult to manufacture not to mention heavy and expensive this is where a chap called Augustine Jean frenel came along he realized you can actually take a chunk out of the center of the lens think about it if a ray of light comes into the missing chunker an angle let's call it Theta is going to be bent away from the normal due to the lower density of air compared to Glass it will then continue on until it hits the other side of the missing chunk where it's going to bend back towards the normal he's going to exit the missing chunk at the same angle it had entered so if it works for one missing chunk it's going to work for others too so you may as well take out loads of chunks and really hack away at that weight you're then left with a series of curved triangles along the original curvature of the lens all you then do is close the air gaps bringing the curved triangles back to a flat surface creating a fresnel lens it behaves in the exact same way as the original lens except it's much smaller and easier and cheaper to build coming back to our Lighthouse light you can place one of these fresnel lenses in front of the light as well as a few other lenses above and below and you can actually capture pretty much all of the light from one side of the source and send it down the focal plane of the light this now makes a parabola completely redundant because anything hitting that would subsequently be deflected away from the focal plane by that massive lens instead you may as well put another set of lenses on the other side and focus the light in that direction too in fact what fresnel actually did was put multiple lenses around the light effectively creating a lantern with many highly focused beams of light you could then simply vary the rotational speed to create the illusion of a regularly flashing light to observe us at Sea it's said that this Revolution by fresnel is the one that saved over a million ships of course incredible as it is there is still one major drawback is only going to work at night during the day you're never going to see the light because the sun is so overpowering instead you're going to be looking for the lighthouse building itself typically lighthouses are placed on cliffs or rocks where any brick or stone building is going to blend in quite well even out at Sea a Greystone building is going to blend quite well into the sky this is after all why warships are gray The Simple Solution is to just paint them a distinctive color so they'll show up against their background this is why your typical image of a lighthouse shows them with red and white horizontal stripes it's simply there to make sure they show up in the daytime where fresnel's breakthrough saves ships at night the paint saves them in the day but what about places where you can't build a lighthouse maybe the seabed is too unstable or it just isn't economically viable well this is where light ships come in they have the exact same technology as lighthouses the same height considerations the same distinctive daytime colors and the same for NL lenses for creating a bright focus light at night the only different is that they're mounted on a ship's Hull and anchored in position making them infinitely cheaper and easier to deploy of course modern electronic navigation has somewhat reduced the benefits of both light houses and light ships but they do still have their place lighthouses are now mostly automated and still found around the coasts of the world in some cases their original rotating lenses have now been replaced by a circular lens with flashing electronic lights instead but other than that all the principles remain the same like ships on the other hand are now much rarer in the United States for example they've now decommissioned all their light ships having replaced them with large boys and one or two permanent structures they do still exist in places like the UK though with probably the most famous examples being the van and zendetti-like vessels in the Dover Strait for those of you interested in hearing a little more about lighthouses and things the director's commentary for this video has just gone live in the community for second mates and above the link to that is in the description down below

Channel: Casual Navigation

Views: 469,770

Keywords: casual navigator, marine, shipping, casual navigation, maritime explaination, merchant navy, sailing, marine animation

Id: CE7bZlb1FfE

Length: 5min 58sec (358 seconds)

Published: Fri Apr 14 2023