Learn about glow-in-the-dark cities; why holes feel larger with a tongue than a finger; and the maximum volume on Earth.
Learn about glow-in-the-dark cities; why holes feel larger with a tongue than a finger; and the maximum volume on Earth.
Maybe we can save the planet by making our cities glow in the dark by Briana Brownell
Why holes feel larger with your tongue than with your finger by Grant Currin
There's a maximum sound volume on Earth by Cameron Duke
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CODY: Hi! You’re about to get smarter in just a few minutes with Curiosity Daily from Discovery. I’m Cody Gough. Today, you’ll learn about how we could save the planet by making our cities glow in the dark; why holes feel larger with your tongue than with your finger; and the maximum sound volume on Earth.
Let’s satisfy some curiosity.
Imagine walking around your neighborhood at night. But instead of bright streetlights, the streets are filled with soft, ambient light glowing from buildings, sidewalks, and roads. It might seem like a stretch, but a group of scientists is developing a series of new materials that could light our cities at night… using luminescent materials, rather than light sources.
Now, this isn’t just aesthetics - it’s also good for energy efficiency. Lighting is responsible for about 20 percent of global energy use. Reducing this energy usage would go a long way in helping combat climate change.
Scientists have been studying luminescent materials for over four centuries. Instead of emitting heat immediately, these materials trap the energy of photons that hit it, and then re-emit them later -- as visible light.
The first luminescent material was created in 1603 by Vincenzo Casciarolo when he smelted some stones he found on Mount Paderno [puh-DARE-no], Italy, and found that they would glow after being exposed to sunlight.
Since then, scientists have found lots of other luminescent materials. There are 250 that we know of. Most of the materials glow blue or green, but there are a few that could give us a rainbow of options: yellow, orange, and red.
Scientists are still studying their properties, and they’ve found a bunch of promising new materials that could be used in buildings and city infrastructure. For example, strontium [straan-tee-um] aluminate can be made into paint that glows for hours after being exposed to light.
That’s the challenge, though. Even if the materials are “charged” by the sun during the day, they would fade before the sun came up the next morning. Better materials that glow longer will help, but we might have to charge them through the night using shorter bursts of artificial light.
The heat that is reemitted by cities is also a problem, especially as global temperatures increase. Cities are on average about 8 degrees celsius warmer than the countryside around them. That means even more energy needs to be used in order to cool the buildings down. A vicious cycle of energy wasted.
Cool materials that are light reflective help cause less of the heat to be absorbed, but scientists think that luminescent materials can do an even better job of absorbing heat and making the buildings cooler. Instead of just bouncing the energy off of the materials back into the air, it transfers energy out. Adding luminescent materials to concrete made the air temperature around them cooler by over 3 degrees. Not bad!
Scientists hope to see luminescent materials used in cities soon, and this research is a shining example of how we might remake our cities in the future. Well…. Glowing example.
Have you ever bitten the inside of your mouth so hard you were afraid the wound would never heal? The gash probably felt huge when you explored it with your tongue, but there’s a good chance it didn’t seem so bad when you looked in the mirror or felt around with your fingers.
It turns out that our tongues reliably overestimate the size of [*half beat*] holes. Researchers probing the question point to the tongue’s flexibility as a key factor.
This phenomenon is called the oral size illusion, and researchers have known about it for decades. In 1988, researchers brought 30 participants into a lab, blindfolded them, and gave each of them two contraptions studded with dozens of different-sized holes. They were told to feel the holes on one contraption with their fingers and holes on the other contraption with their tongues. Their task was to match holes that were the same size.
Turns out, they were pretty awful at it, at least for holes that were smaller than one centimeter in diameter. That’s about three-eighths of an inch. They consistently overestimated the size of the small holes they felt with their tongues.
Weird, right?
Fast-forward three decades. A different set of researchers are asking a new question: Why? Several hypotheses had sprouted up to explain the illusion, so they conducted several rounds of experiments to compare those explanations. They added a twist, though. In addition to tongues and fingers, the researchers added big toes into the mix.
Experts had proposed two types of explanations for the oral size illusion. So-called lower-level explanations pointed to the physical differences between tongues and fingers. Maybe the illusion happens because tongues feel in higher resolution than fingers. Or maybe it’s because the tongue is more pliable. So-called higher-level explanations suppose the answer lies in the brain. Maybe our brains are wired to assess the size openings based on how easily our bodies — or parts of them — can fit through them. The lower-level explanations focus on how information gets into our bodies while the higher-level explanations are interested in how our brains process it.
After running five tedious rounds of experiments, the researchers concluded that the lower-level explanations did a much better job at explaining the results than the higher-level ones. The evidence clearly shows that the most important factor in the oral size illusion is how closely the surface of the body is able to bend in and around the perimeter of the hole. The tongue is a flexible muscle covered with a mucous membrane. It can really get in there and gather a lot of information. The fingers and toes, on the other hand, are bones covered in muscle, fascia, and skin. Those surfaces are less pliable than the tongue, they collect less information, and that leads to more accurate measurement.
Yes, less information leads to more accurate measurement. It’s a paradox.
When we measure sound volume, we tend to think about it in terms of decibels. The more decibels, the louder something is. But how high does it go? Believe it or not, there is a maximum sound volume on Earth.
Before I get to that though, first let’s talk about what sound is and how we measure it. Sound is basically a pressure wave traveling through something physical, like water or air. That pressure wave causes molecules to rhythmically push and pull on each other, which, in turn, does the same to your eardrums. Volume, or loudness, is just a measure of how powerful that pushing and pulling is.
The decibel scale tells us how much energy a sound wave has. A normal conversation might clock in at fifty decibels, while your garbage disposal is around eighty. At 110 decibels, sound becomes quite uncomfortably loud. This rapid increase in intensity has to do with the fact that the scale is logarithmic, not linear. So, an increase of ten decibels from ten to twenty isn’t a doubling in volume, it’s a tenfold increase.
The loudest ever natural sound ever recorded was the eruption of the volcano Krakatoa in 1883, which was measured at 172 decibels from 100 miles away. By the way, 130 decibels is typically referred to as the “threshold of pain,” so be thankful you weren’t around for that.
Theoretically, the scale has no upper limit. But here on Earth, it has a physical one: 194 decibels. At that volume, the waves are creating a complete vacuum between themselves, essentially producing a natural sound ceiling.
Now, technically, louder sounds are possible, but they are distorted. You know how screaming into a microphone overloads the mic and causes distortion? Well, the atmosphere does the same thing. It simply can’t handle sounds that loud. At that high of a level, you end up with more of a shockwave and less of a soundwave. Setting aside that technicality, though, there are a couple times we’ve pushed past that 194 decibel barrier that are worth mentioning.
The loudest sound ever accurately recorded was a pressure wave produced by the launch of a Saturn V rocket. Its volume was recorded at 204 decibels. Perhaps the loudest, strongest pressure wave ever produced came from the largest ever bomb explosion, the Tsar Bomba [ZAR bomb-ah], which according to the most reliable estimates, likely produced a Tsar Boom-ba — that is, a 224 DB shockwave. That bomb could have killed with sound alone.
...and they say looks can kill.
Let’s recap what we learned today to wrap up. Starting with
[ad lib optional]
CODY: Today’s writers were Briana Brownell, Grant Currin, and Cameron Duke. This episode was produced and edited by me, Cody Gough. Curiosity Daily is distributed by Discovery.
Hear. Feel. Think. And join us again next time to learn something new in just a few minutes.
And until then, stay curious!