¿Por qué las luces de las calles de EE.UU. se están volviendo moradas?

0:00 If you've walked around your neighborhood lately at night taking out the trash or walking the dogs, you may have seen a street light that looks like this in a sea of normal street lights. There are one or two or sometimes even a whole block of them that are purple. It 's a little hard to miss, isn't it? And the strangest thing is that it's been happening all over America for years up to this point. Since 2021, hundreds of local news stories, thousands of TikTok and Reddit threads have covered the topic. And whatever you call the former publications have now reported the phenomenon and the purple lights just keep popping up everywhere. Apparently at random. So what's really going on here? Is purple light easier on the eyes at night? Is it better for the

0:46 safety of alien pedestrians? It's actually a big problem and it comes down to how LEDs work, poor quality control, and good old government contracts. So I'm going to explain to you why America's roads are turning purple and how we can't seem to stop it. [Music] In recent decades, home lighting production has shifted from incandescent bulbs to fluorescent and LED, as well as street lights. In the 20th century, sodium vapor lamps with a mixture of neon, argon and metallic sodium produced yellow light on every street. Sodium vapor lamps were used since the 1930s, as their yellow light was the best for penetrating fog.

1:32 The idea that yellow light cuts through fog better is still seen in off-road vehicles and aspiring dirt bike racers. The longer wavelength of yellow light prevents it from easily reflecting off water droplets in the air. The longest wavelength would be red. That's why we use red lenses for brake lights. But for street lights it is not the light itself that we want to see. It is what the light is illuminating. And for that to work, our brains need to fully understand what we're seeing. And that requires full-spectrum light like we get from the sun. So, over time, streetlight manufacturers figured out how to increase the pressure in sodium vapor lights to create more full-spectrum light. Everyone knows the rainbow, right? Like every corporate logo in June, a

2:20 full-spectrum light produces all the colors of the rainbow, which combined look white. High-pressure sodium vapor lamps were used in sports stadiums and large event areas. If you were around in the 90s, you would have seen the difference in quality between low and high pressure lights. The broader and more uniform the light spectrum, the more it resembles sunlight. This means that it makes more sense for our brain, but it also demands more energy. Therefore, older neighborhoods might have had low-pressure sodium vapor lights , while newer buildings would have had high-pressure white lights. The problem with sodium vapor lamps is that they are relatively inefficient. Because of the amount of light they create, they also generate a ton of heat.

3:05 When the goal is to generate light, heat is wasted energy. They also scatter light in all directions instead of focusing the light where we need it. LEDs are much more efficient at creating light compared to incandescent bulbs. As you may have noticed at home. Before, you couldn't unscrew a lit light bulb because it would be too hot. Now that almost all lights are LED, you can just use your mouth, but really don't do that for multiple reasons. Compared to incandescent bulbs, LEDs were nearly 10 times more efficient, with 90% of the power going into producing light. However, compared to sodium vapor, the actual amount of light per watt is not that much of a jump. But factors such as directionality and

3:50 bulb lifespan, which are important in the long run, led almost all cities to begin replacing their streetlights with LEDs. When this happened, you could literally see the change. The streets, which had previously appeared orange or yellow, were now bright white. This change was a problem for the film industry. There was concern that shooting period films in big cities would suddenly become much more expensive because white lights made everything look too modern, and then making them all yellow again on set or in the editing room would be very expensive. Difficult filming is a specific problem that arises when changing street lighting at night . But I bet if you ask anyone you know what they think about LED street lights—and I mean the functional

4:35 white ones, not the purple ones—they'll say they hate them. The light is harsh, it is cold and too bright. People feel this way not only because no one likes change, but because those lights aren't really white. They produce blue light like your phone or computer. You know, those things that doctors recommend you avoid watching before bed because they affect your sleep, although this isn't necessarily bad for street lighting. Cool blue or white light increases alertness and improves memory and brain function. essential items for driving at night, but it 's also that little truth that helps us understand why everything is turning purple. So technically there are no white LEDs. For an LED to emit white light, the process is very

5:20 different from that of high-pressure sodium vapor or the sun. Remember the rainbow I mentioned? The one on the cover of The Dark Side of the Moon. That is the visible spectrum of light. The sun produces radiation at every wavelength in that spectrum and a host of other wavelengths, including ultraviolet, but it doesn't produce them equally. This is called the spectral distribution and describes the average bias of how light appears. If you're into photography or interested in your light bulbs, you 've seen this measured in Kelvin. Sunlight is approximately 5600º Kelvin. Incandescent bulbs have a color temperature of about 3200 Kelvin, giving them a warmer tone despite their cooler temperature . That's backwards and confusing, but let's not get into that. The point is that both

6:06 the sun and incandescent bulbs were full-spectrum sources with different average color temperatures . The problem is that individual LEDs don't produce the full spectrum, they produce primarily one color. You have red, green or blue RBA. With a few marginal exceptions in terms of the materials available for mass-produced products like street lights, we have these three to work with to achieve white light. On a monitor or phone, each pixel on your screen produces equal amounts of red, green, and blue to create white light. In street lights, manufacturers use blue LEDs in a process called phosphor conversion. In simpler terms, the blue LED shines through a laminated yellowish filter made of phosphor and silicone which

6:52 simply converts it to white light. White light that is still a little too blue for comfort. And guess what, a number of manufacturers did a pretty poor job of making that filter layer, including American Electric Lighting and Acuity Brand Lighting, which together are responsible for tens of thousands of the defective lamps in several states. And over time, the filter delaminated, developed cracks, or simply fell off the LED module altogether. If it fails completely, you end up with a completely blue street light. If somehow held in place, the blue light source interacts with the remains of the yellow filter and emits purple light. That's why some people say they're turning purple and others say it 's blue. It's both. And either

7:39 way, it's a literally shining reminder of your local municipality's failures. But why are we only starting to see this in 2021? Well, because the 2010s saw the first big push by federal and local governments to replace old sodium lights with new, eco-friendly LED lights. It turns out that many millions of dollars were spent on streetlights that were simply defective. At least money was cheap back then. That's your answer. Street lights are turning purple and blue due to a simple manufacturing defect that, through political and economic forces, eventually appeared in every single state in America, not to mention a number of other countries. When we first started seeing purple street lights, many

8:26 speculated that they might improve nighttime visibility or pedestrian awareness. And sadly, that's not the case. True blue light does not give you any night vision advantage over warmer lights. In fact, it makes it difficult to see details and the transition from light to dark. But there are other colors that could help with that. There is a small Dutch town that is known for its red lights. I'm not talking about Amsterdam, I'm talking about This, you can see it. The town has adopted red street lights to help its residents see at night, and not just its human residents. The region is home to large populations of several rare bat species. While blue streetlights help us see better at night because they mimic the sun, they also disrupt the

9:12 natural daytime cycles of bats, insects, and other animals. Therefore, red LED street lights provide illumination while reducing negative effects on local wildlife. It also protects night vision. If you've ever wondered why camping headlamps or torches have a red setting, here's why. The longer wavelength of red light means our eyes don't have to adjust as much when moving from light to dark. This is why the brake lights are red and I have never been dazzled by the LED taillights. The only problem with red street lights is that we've already unanimously decided that a red light means stop. We are not ready for that level of change. Whether the lights in your neighborhood are red, purple, white, or yellow, the bottom line is that

9:59 they're there. I live in one of the few neighborhoods in Los Angeles that doesn't have streetlights. I tell you that it gets very dark at night. I prefer a dwelling. At least so far, no accidents or other serious incidents have been reported directly caused by the purple lights. But I do n't think we can feel good about our city spending so much money on lights that lasted less than 5 years, even if the intention was good. I mean, sure, LED street lights are brighter and more energy efficient, I just wish we spent a little more time looking for suppliers who were a little more competent. Where does that leave us ? Aside from paying for a lot of replacement lights. The good news is that over the past five years, LED technology has advanced to the point where manufacturers can get pretty close to the warm

10:46 glow of old-fashioned lights. You may have already noticed newer, more eye-pleasing street lights than the first round of LEDs before they failed, but for now, just keep an eye out for the purple lights and let your local government know that they're broken. All good? Good. See you in two weeks. Thanks for watching.