To wrap up our Shark Week coverage, learn about why the US military tried to develop shark repellent during World War II. Then, learn about the leading theories explaining why moths are drawn to lights; and the difference between mummies and fossils.
To wrap up our Shark Week coverage, learn about why the US military tried to develop "Shark Chaser" shark repellent during World War II. Then, learn about the leading theories explaining why moths are drawn to lights; and the difference between mummies and fossils.
Get even more from Shark Week 2020 on Discovery’s Daily Bite Podcast: https://www.discovery.com/shark-week/everything-you-need-to-know-about-the-daily-bite-podcast
During WWII, the US military tried to develop shark repellant by Cameron Duke
We still don't know why moths are drawn to lights by Grant Currin
What's the difference between a mummy and a fossil? by Ashley Hamer (Listener question from Luke)
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Find episode transcript here: https://curiosity-daily-4e53644e.simplecast.com/episodes/why-the-us-military-made-shark-repellant-why-moths-are-drawn-to-lights-and-the-difference-between-mummies-and-fossils
CODY: Hi! You’re about to get smarter in just a few minutes with Curiosity Daily from curiosity-dot-com. I’m Cody Gough.
ASHLEY: And I’m Ashley Hamer. Today, you’ll learn about why the US military once tried to develop shark repellent; and why moths are drawn to lights. We’ll also answer a listener question about the difference between mummies and fossils.
CODY: Let’s satisfy some curiosity.
During World War II, the U.S. military developed and deployed shark repellant. But, spoiler alert: It didn’t work.
Here’s the story. World War II was the first time Americans fought a war in tropical seas, and inevitably, that led to rumors about shark attacks. Pilots and sailors were pretty scared about the potential predators that lurked in the ocean beneath them, and the rumors didn’t help.
The Navy decided they could easily solve their morale problem by solving the shark problem. Their answer? Shark repellant, obviously. So the Office of Strategic Services, or OSS — the 1940s version of the CIA — assembled a scientific development team that, curiously, didn’t include any shark scientists. That wasn’t an oversight. In 1942, shark scientists didn’t really exist.
Besides that, though, there was one other small problem: there were no confirmed records of sharks killing servicemen. Zero. The Navy knew how rare shark attacks were. They at least wanted what they called a “pink pill,” or something that would make their pilots feel better, even if it didn’t work.
So, scientists at Woods Hole Oceanographic Institute got started. A team of chemists (that included an early-career Julia Child) tested 79 substances, ranging from clove oil to nicotine to horse urine. The scientists would drop each chemical in tanks containing dogfish sharks — a small, timid species of shark. But none of the substances seemed to bother them. Eventually, the Navy settled on an attempt to obscure the shark’s vision by mimicking squid ink. The result was a packet containing something like a urinal cake that would slowly release an inky black liquid. They called it Shark Chaser.
Unfortunately, the inky black liquid dissipated too quickly to be useful, and as far as anyone knows, Shark Chaser did nothing to deter sharks. In the 1970s, the US Navy officially declared Shark Chaser useless. But scientists haven’t stopped working on a real shark repellant. But this time, it’s to steer sharks away from commercial fishing nets. The first shark repellant was designed to protect humans from sharks — but its real promise may be in protecting sharks from humans.
Moths have a thing for light. Walk out the door after the sun goes down in late summer and you’re all but guaranteed to see a small swarm fluttering around your porch light. Believe me, I know: which is why I never turn on my porch light. Have you ever wondered why they flutter around lights like… well, like moths to a flame? Scientists have a couple of theories, but the general answer might disturb you: they don’t really know.
What they do know is that most moths, but not all of them, are drawn to light. They even have a term for it: positive phototaxis [FOH-toh-TAX-suss]. Moths like the wavelengths of light we humans can see, but they’re even bigger fans of ultraviolet light, which we can’t.
It’s possible that moths are so attracted to light because they’ve evolved to navigate using celestial cues. Before the advent of the campfire — and later, the lightbulb — the moon and stars were basically the only things shining brightly at night. According to the navigation theory, moths orient themselves by following a flight path that keeps the moon at a constant angle relative to their eyes. The problem is that porchlights, streetlights, and floodlights get in the way of this natural means of navigation, which leads moths to try navigating by some cheap moon impostor.
At this point, you might have already spotted a problem with this theory. Moths definitely don’t keep their target light at a constant angle relative to their eyes. They swoop, and dive, and do little moth cartwheels. Hardly evidence for an internal navigation system fixed on your front porch.
According to a different theory, the thing that gets those moths all hot and bothered is love. When females pump pheromones into the air, they also release a little bit of electromagnetic radiation that’s on the infrared end of the spectrum. It’s possible that male moths can use their antennae to detect the specific wavelengths that correspond with those pheromones. It just so happens that some of the electromagnetic radiation produced by candles and some artificial light sources has the same wavelength as what female moths produce.
Buuuut this isn’t a very convincing theory either. One reason is that moths prefer ultraviolet light to infrared rays. Another is that this doesn’t explain why both male and female moths are drawn to lights. Even though moths have been drawn human-made light for thousands of years, we still can’t explain why. There are still some mysteries left in the world.
We got a listener question from Luke, who asks, “How long can mummified skin (or hair or nails) survive under ideal conditions? Is human mummy skin "real skin" but dinosaur skin, where found, is actually just minerals that replaced it over time?” Interesting question, Luke! Let’s get to the bottom of it.
At first glance, mummification and fossilization have a lot in common: both of them protect a dead organism from decomposing and keep it preserved for a really long time. But mummies aren’t just a younger version of fossils. In other words, King Tut isn’t going to turn into stone in a few millennia. Mummies and fossils form under different conditions.
Human mummy skin is real skin. A mummy can be formed via human intervention or naturally — it can happen in bogs, ice, or desert air. But either way, the preservation is made possible by keeping bacteria and fungi from growing on the body. That can happen through drying, freezing, oxygen deprivation, or with certain chemicals. The final result is still real human tissue, just dried and preserved in a way that will keep it looking pretty much the same for thousands of years. We don’t know exactly how long mummified skin can survive, but we do know that the world’s oldest mummies have been around for nearly 9,000 years. Those are the Chinchorro mummies of Chile, and unfortunately, they may not last much longer. Climate change is leading to a rise in humidity, which is reversing that careful drying process. As a result, the mummies are beginning to rot. Definitely not ideal conditions there.
Fossil skin, on the other hand, is stone. The youngest fossils we have are 10,000 years old — though that number is just a technicality. Paleontology as a field just decided that anything 10,000 years old or older is a fossil; anything younger than that is considered a “sub-fossil.” Whatever. But fossils require their own very particular preservation process. Specifically, they need to be buried under sediment. Most often, that’s underwater, like a lake or riverbed or the ocean floor. As organic parts of the bone break down, minerals in the water rush in to fill the gaps. Eventually, the whole bone turns into minerals — also known as rock. If the conditions are just right, this can happen with soft tissue like skin, too. It’s rare, but it has happened: paleontologists have found so-called “mummified” fossils of feathered dinosaurs in China, duck-billed dinosaurs in North America, and an astonishingly well-preserved nodosaur in Western Canada. These fossils let scientists glimpse the skin, muscles, and sometimes even stomach contents of animals that lived millions of years ago.
But even though we call them mummified fossils, they’re entirely made of rock. That’s the difference. Thanks for your question, Luke! If you have a question, send it in to podcast at curiosity dot com. Or leave us a voicemail at 312-596-5208!
Leave us a voicemail at 312-596-5208!
CODY: Before we wrap up our final Shark Week episode, we want to let you know about another podcast to help you get your shark fix. Discovery’s Daily Bite Podcast features marine biologist Luke Tipple doing exclusive interviews with the stars of Shark Week. Check it out to learn from the top shark scientists on the planet, and get a behind-the-scenes take on what really happened when they were out on the ocean. To listen and learn more about the podcast, go to Discovery-dot-com-slash-DailyBitePodcast. We’ll also put a link in today’s show notes.
And now, here’s a sneak peek at what you’ll hear next week on Curiosity Daily.
ASHLEY: Next week, you’ll learn about why you create false memories of doing daily tasks;
The world’s first nuclear reactor with a 3D-printed core;
And why it’s harder to clean grease off of plastic than glass.
CODY: You’ll also learn about a new field of study called “environmental cardiology,” from one of the researchers who pioneered it: Dr. Aruni Bhatnagar [BOT-nah-GAAR]. Okay, so now, let’s recap what we learned today.
[ad lib optional]
CODY: Today’s stories were written by Ashley Hamer, Grant Currin, and Cameron Duke, and edited by Ashley Hamer, who’s the managing editor for Curiosity Daily.
ASHLEY: Today’s episode was produced and edited by Cody Gough.
ASHLEY: Scriptwriting was by Cody Gough and Sonja Hodgen. Curiosity Daily is produced and edited by Cody Gough.
CODY: Have a great weekend, and join us again Monday to learn something new in just a few minutes.
ASHLEY: And until then, stay curious!