Episodes

  • Why do sharks have multiple sets of teeth? Why do sharks lose so many teeth? Do sharks eat fish? How do sharks breathe underwater? Do sharks sleep? Give a listen to this totally jaw-some conversation about sharks with Dr. Kady Lyons, shark researcher at the Georgia Aquarium! We also tackle: Why are dinosaurs extinct and sharks are not? Were megalodons the biggest sharks in the world? Do sharks have noses? How do sharks communicate? Why do sharks bite? Why are sharks dangerous?

    Download our learning guides: PDF | Google Slide | Transcript

    Sharks are a type of fish. They’ve been around for millions of years and their body plan hasn’t changed much in that time!

    Sharks’ skeletons are made of cartilage. They don’t have any calcified bones - so the only part of a shark that gets left behind in fossil records is their teeth!

    Megalodons were the biggest shark, but they are extinct (despite sensational TV shows that claim otherwise). The latest research suggests megalodons were bigger than modern day humpback whales!

    Sharks and other fish breathe by extracting oxygen from water by the use of their gills. Gills are made of very thin tissue. The blood inside the tissue picks up oxygen from the water and brings it into the organs in the fish’s body.

    Sharks evolved to have sharp teeth to grab slippery fish and other prey. If they break a tooth, they can regrow a new one, and they just drop the old one. Easily replacing a tooth that breaks off is a strategy that allows them to keep hunting. Their teeth grow continually through a shark’s life, moving forward in their mouth kind of like on a conveyor belt, maturing as they go. So when a tooth falls out a new one moves forward. Some sharks lose whole rows of teeth, like dentures, all at the same time.

    All sharks are carnivores, eating fish, seals, and sometimes other sharks. Some species, like whale sharks, filter feed, mostly on zooplankton but sometimes phytoplankton (sea plants) as well.

    Sharks have been known to attack humans, but humans actually aren’t great prey for them because we lack a thick layer of blubber or other energy the sharks are on the hunt for. Usually sharks attack when they mistake a human for something else, like a seal.

    Sharks go through periods of sleep or rest, reducing brain activity.

    Sharks have a fantastic sense of smell. It helps them find their prey.

  • How do popcorn kernels pop? How do salmon know where to return to spawn? How do rabbits change colors? Why does television fry your brain? How do zippers zip stuff? Who was the fastest runner in the world? In this episode, we'll tackle all of these questions!


    Download our learning guides: PDF | Google Slide | Transcript

    Inside the husk is a tiny little droplet of water surrounded by something called the endosperm. The endosperm is what you're actually eating when you eat popcorn. When you heat up popcorn, the tiny droplet of water gets hot and turns into steam. That steam pushes through the endosperm and turns it kind of soft and that endosperm builds up pressure and explodes through the husk. When it explodes, that soft gelatinous endosperm hits cooler air and it hardens up in whatever shape it has exploded into. So that's why popcorn has all those funny shapes and feels kind of like foam.

    Salmon are born in freshwater, but then spend their lives in saltwater. They return to the freshwater to spawn (lay and fertilize eggs) and die. Some salmon return to any body of freshwater to spawn, but some salmon have special ways of finding their way back to the place they were born. They use a kind of internal compass to head back to the spot. Other fish rely on their sense of smell to find their way back to fresh water.

    Animals that turn white in winter use the length of day as their cue to stop producing pigment in their fur. Their bodies can sense the hours of daylight, and when the daylight starts getting shorter, their hormones will tell the cells to stop producing melatonin. Hormones tell the cells what to do to shut off the production of pigment in the fall and to turn it on again in the spring. It's not because the days and the nights get colder or warmer.

    The fastest runner in the world is Usain Bolt. He's the fastest man who's ever been timed. He's a Jamaican sprinter, and he holds the world record for both the 100 and the 200 meter sprints. He has nine gold medals at the Olympics and 11 world championships. His record for the 100 meter sprint is 9.58 seconds. That is super fast. That's more than 23 miles an hour.

    Want to pop your own popcorn from kernels? Find a big pan with a tight-lid. Pour two tablespoons of cooking oil in the pan. Then add a half a cup of popping corn. Cover the pan and turn the heat to high. In a few minutes the popcorn will start to pop. Turn off the heat. Open the lid when the popcorn stops popping. Enjoy!

    How a zipper works

    Sounds Wild

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  • Field trip time! Today we’re learning all about snakes while out on a search for timber rattlesnakes in New York with state wildlife biologist Lisa Pipino. Some of the questions we tackle: How do some snakes make venom? Why are some snakes venomous and others are not? Why do rattlesnakes have a rattle? How do snakes slither on the ground without legs? Why don’t snakes have legs? Why don’t snakes have ears? How do they smell with their tongues? Why do some snakes use heat vision? Do snakes sleep? Why do snakes stick out their tongues so much?

    Download our learning guides: PDF | Google Slide | Transcript

    Snakes are ectothermic - meaning they are cold-blooded and rely on their environment to regulate their body temperature. Snakes like to bask on warm rocks to stay warm.

    A rattlesnake’s first rattle segment is called a button. They shed their skin once or twice per year and each time they do, they get a new rattle segment.

    Rattle segments sit on top of each other, and when rattlesnakes shake their tail, the segments rattle. This noise is a warning to predators to stay away.

    Some snakes lay eggs. Others develop eggs that grow and hatch inside their body, meaning the snakes give birth to live young. Rattlesnakes give birth to live young but only stay with their babies for about a week. Those babies follow their mother’s scent trail back to the den for winter.

    Some snakes are venomous, but not poisonous. What’s the difference?! Venom is delivered through a bite or a stinger, while poison is usually inhaled, swallowed, or absorbed through the skin. Snake venom is a lot like saliva, except it’s toxic. Snakes create it using a special gland. They then use their venom to immobilize or kill their prey before they eat it. They sometimes use their venomous bite as a defense as well.

    Snakes do have nostrils and can smell through their nose a little bit. But they mostly use their tongues to smell and sense their environment. They stick out their tongues to pick up scents. And then they rub their tongues on a special organ at the top of their mouths, which sends a message about the scent to their brains.

    Timber rattlesnakes live in the Eastern US and are different from some of the other well-known rattlesnakes in the Western US. In much of the northeastern states they’re considered threatened or endangered. People shouldn’t try to look for these snakes because of the possibility of disturbing the snakes or their habitats.

  • Why do we feel pain when we get hurt? What is pain? Why do we cry when we get hurt? Why do we say ow or ouch? We’re learning about how pain works with Joshua Pate. He’s a physical therapist and author of a forthcoming children’s book series about pain.

    Download our learning guides: PDF | Google Slide | Transcript

    Pain happens when your body sends signals to your brain that something is wrong. And your brain sends signals to your body to feel pain! Pain is protective–it lets us know to stop doing something that is damaging or might damage our bodies. And it lets us know that something is wrong and we might need to get help from an adult or a medical provider.

    When you get hurt, like scraping your knee for example, the nerve cells in the knee send a message to the brain. Your eyes might see the scraped knee and send another message to your brain. Then your brain has to decide how much danger your knee is in. Pain is messaging that lets your brain know that something is not well. If you didn’t have that pain, you might keep scraping your knee over and over.

    Pain is biopsychosocial, meaning biology, psychology and social or environmental factors all play a role in what pain feels like for individual people.

    A lot of things can turn the feeling of pain up or down. Distraction, like listening to music or watching a video can help turn pain down. Staring at the source of pain can make it hurt more.

    Outside factors can also impact pain. In a study from several years ago, people were asked to hold a freezing cold rod. Scientists changed the colored lights in the room. When the lights were blue people felt less pain from the rod than when the lights were red.

    Normally, pain will recede when an injury heals. But not for everyone. Sometimes people suffer from chronic pain after an injury.

    We cry when we’re in pain as a way of letting others know that something is wrong. We also learn to use the words ow or ouch. Other languages have different words for pain.

  • Why do friends care about each other? How do you make friends? Can you have more than one best friend? How do you deal with a bully? We answer questions about friends and bullies with Dr. Friendtastic (also known as Eileen Kennedy-Moore), a psychologist and author of Growing Friendships: A Kids’ Guide to Making and Keeping Friends. And we get lots of advice from kids themselves about how to make friends and deal with bullies.

    Download our learning guides: PDF | Google Slide | Transcript

    Friendship is often about action. It's about what we do together, how we treat each other. The key to friendship is kindness.

    Best friends are nice, but the word “best” can make it feel like a contest. Most people have different friends and for different situations. So it’s okay to have several close friends instead of needing to identify just one best friend.

    Some people have lots of friends, but other people may just have a few close friends. People with more friends tend to put more effort into having more friends. It’s okay to have a lot of friends or just a few!

    To make friends, you have to show an openness to friendship. That can be as easy as smiling or saying hi. It’s also important to be kind to potential friends. And it also helps to identify people who have similar interests to you. Then, invite them to do something. Kids make friends by doing fun things with other kids. Don’t wait until you feel close to someone to invite them to do something; you become close by doing shared activities.

    Shy people might be unintentionally sending the message to potential friends that they don’t like them. Stop focusing on being uncomfortable and instead look the other kid in the eye (or the forehead if eye contact is hard for you), smile and say hello. Practice it with an adult.

    At recess or on the playground, bigger groups of kids will be more open to you joining than groups with just two or three kids.

    Research shows that instead of asking if you can play with a big group, hang back and watch for a few minutes to figure out the game the other kids are playing, and then just join in. If you ask “Can I play with you?” you risk interrupting the play.

    Bullying is deliberate (intentional) meanness directed at one person where there is an imbalance of power. For example, an older or more popular kid picking on a younger or less popular kid.

    It’s important to know the difference between bullying and meanness. Bullying requires adult intervention. If you’re having a problem with a friend that is not bullying, you may still want to talk that through with an adult, but it’s often possible to handle that conflict with your friend on your own.

  • How are crickets so loud? Why do they chirp at night? How are they different from grasshoppers? We’re talking crickets today with Karim Vahed, a cricket and katydid expert and entomologist (bug scientist) at the University of Derby in the United Kingdom. Professor Vahed also takes on some of your pressing insect questions: Do insects have bones? What do baby bugs like to do? Do insects drink water? Why are bugs so important?

    Download our learning guides: PDF | Google Slide | Transcript

    There are over 9,000 known species of crickets on the planet. These insects are best known for singing and hopping!

    Insects are divided into different orders depending on what kind they are. Crickets are in the order known as Orthoptera, which contains grasshoppers, locusts, crickets and bush crickets, and katydids.

    Crickets and grasshoppers are different! For one thing, most grasshoppers make noise by rubbing one of their legs against one of their wings. But most crickets make sound by rubbing their two forewings (their front wings) together. One wing is jagged, like a little row of teeth. And the other wing kind of scrapes up against it, making a sound.

    The number of teeth on the scraper, the speed of the rubbing and how frequently they make the chirps differ depending on the species. So there are lots of different cricket songs.

    Try an experiment: Get a comb and run your fingernail across it. See if you can make a sound. If you have more than one comb, or a comb with two differently sized/spaced teeth, see if they make different sounds. Does the size of the fingernail make a difference in the sound? Try giving your comb to an adult and find out!

    In most cricket species, the males chirp to attract a female. And they mostly sing at night to help avoid predators.

    But Karim Vahed says some studies have shown that predators like domestic house cats follow the chirps of the crickets to find and eat them!

    Imagine a cricket the size of a hamster! A cricket so big it would cover the palm of your hand if you were holding it. The giant wētā [say it: WEH-tah] is that insect! There are several species of giant wētās. They all live in New Zealand and most of them are protected because they’re quite rare.

    Insects are the most diverse group of animals on the planet. There are more than a million known species (about 80% of all known animals). But scientists estimate anywhere from 10 million to 80 million insect species have yet to be discovered!

  • That’s just one of the questions we answer in this week’s episode, which also includes instructions on how to easily make your own ice cream at home! We’ll also tackle the why and how of melting ice cream and why some flavors tend to melt faster than others! Our expert in this episode is ice cream entrepreneur Rabia Kamara, of Ruby Scoops in Richmond, Virginia. It's going to be sweet!

    Download our learning guides: PDF | Google Slide | Transcript

    After listening, if you're ready to try making ice cream at home, here's Rabia's easy recipe.

    INGREDIENTS:

    2 cups of heavy cream

    1 14oz can of sweetened condensed milk

    Optional additional flavorings:

    a splash of vanilla

    pinch of salt

    And whatever else you might want to add! (Chocolate chips, cookie crumbles, etc.)

    INSTRUCTIONS:

    Use a hand mixer to beat the heavy cream until it is the consistency of whipped cream, with peaks that hold their shape.

    Fold any additional ingredients into the sweetened condensed milk and add the mixture to the heavy cream and fold them together using a spoon.

    Put into a freezer safe container.

    Let freeze for about 8 hours.

    Enjoy!

  • The Washington Mystics of the WNBA join us in this episode to answer all of your questions about the sport of basketball and what it’s like to be a professional athlete. How many basketballs does the team have? Why do balls spin when you bounce them? Who invented basketball? Why are basketballs orange with black lines? Why do men and women play on separate teams? How do injuries impact professional careers? And do you have to be tall to play hoops?


    Download our learning guides: PDF | Google Slide | Transcript

    Resources

    Basketball Games for Kids

    Learn More About the WNBA

  • For the past 50 years, visitors to the Smithsonian National Zoo in Washington, D.C. have been able to observe giant pandas. It’s one of the few places in the United States to see these black and white bears. For our latest episode we took a field trip to the zoo to visit the three pandas currently living there and answer panda questions with zookeeper Mariel Lally. We tackle: Why do animals live in the zoo? Why are pandas black and white? Do pandas hibernate? How can we save the pandas? And check out our social media pages for lots of pictures!

    Download our learning guides: PDF | Google Slide | Transcript

    Three pandas live at the National Zoo: adults Tian Tian and Mei Xiang and their cub, Xiao Qi Ji.

    Zookeepers are never in the same space as the pandas. Even though they are herbivores, pandas are still wild animals with sharp claws and big teeth, so it’s important for people to stay safe.

    Researchers at the National Zoo have worked with colleagues in China on a breeding program for both captive and wild pandas. That research has helped pandas go from endangered to vulnerable. They’re still at risk of extinction, but doing better than they were just a few decades ago.

    Pandas eat 100 pounds of bamboo per day! The National Zoo cuts bamboo from sites around the D.C. area, including at some local private homes.

    Researchers aren’t sure why pandas are black and white, but the leading theory is that the white color provides camouflage in their snowy natural habitat and the black fur helps them blend in when they hide in shady bamboo forests. Panda cubs do have predators in the wild.

    Pandas do not hibernate, but they spend their time eating or sleeping. They have a period of deep sleep, similar to the torpor of reptiles. Keepers say they try not to wake sleeping pandas because they get very grumpy! (So the saying, “Never wake a sleeping bear” is especially true for pandas.)

    Zoo pandas get daily training to make their care easier. For example, they learn their names and they are taught to open their mouths and show a paw so they can more easily receive medical care.

    Zoos used to display animals primarily for human enjoyment. Now, most zoos focus on species conservation, research and educating the public about animal species.

    Resources

    National Zoo’s Panadriffic Pack (games and coloring pages)

    Panda Cam

  • When there's mass violence in the news, especially when it involves children, it can be really hard to know how to speak to your kids about what is going on. In this special episode FOR ADULTS, we talk with a child psychologist about some recommended ways to approach these conversations. We first released this episode in 2016, and are heartbroken and angry that it remains so relevant.

    Dr. Robin Gurwitch is a child psychologist at the Duke University Medical Center, and she has served on numerous commissions and committees about children and trauma, including the National Advisory Committee on Children and Disasters.

    Though this episode is for adults, we know children sometimes listen to episodes without adults around, so the information in this episode is intended to be non-traumatizing for children to hear. (Transcript)

    Here are additional links for more information:

    [American Psychological Association](about:blank)

    The National Child Traumatic Stress Network

    The Family Acceptance Project

  • What is climate change? What is causing climate change? How do you cool down the earth? How is climate change affecting the oceans? Kids are hearing about climate change and they have lots of questions. In this episode we explain the science of climate change and look at how humans will adapt to a rapidly warming planet. We speak with Dr. Claudia Benitez-Nelson, oceanographer at the University of South Carolina and Dr. Jola Ajibade, a geographer at Portland State University. This certainly isn’t a comprehensive look at the issue, but it’s a good way to start a conversation about this issue for families and teachers.

    Download our learning guides: PDF | Google Slide | Transcript

    Climate is the long-term trend of temperatures and weather. You can think of the difference between climate and weather like a dog walking down a sidewalk: The dog might go from side to side of the sidewalk - that’s kind of like the weather - it varies. But the general direction of the dog is forward - that’s the climate.

    Since the 1800s we’ve had a lot of changes in technology that mean humans are burning a lot of fossil fuels like oil, gas and coal, to power engines, run our cars, heat our homes and create electricity. That puts a lot of greenhouse gasses and carbon dioxide into the atmosphere.

    The atmosphere is like a blanket around the earth. The increase in greenhouse gasses means that the blanket is getting thicker, making the earth warmer.

    Think of the earth like a human body: when a fever increases our body temperature by a few degrees, it can make you feel really sick (sometimes really hot, but other times with cold shivers). It’s the same thing for the earth! Even one or two degrees difference in average global temperature can make a big difference, including changing the amount of rainfall that a region gets or the overall temperature of the ocean, throwing our systems out of balance.

    Climate change can increase sea levels. As polar ice caps melt because of increasing temperature, the water levels rise, which can cause higher tides and more flooding. A good experiment you can do to visualize this is to grab a mixing bowl and turn a smaller bowl upside down inside of it (like an island). Pour some water and several ice cubes into the big bowl and see how high the water goes up the side of the smaller bowl. (You might need to weigh the smaller bowl down so it doesn’t float up.) As the ice melts, observe how the water level rises up the sides of the small bowl.

    Increased water temperatures are bad for coral reefs and other ocean animals.

    The best way to stop climate change is to stop burning fossil fuels.

    People will respond to climate change through coping mechanisms, including migration and relocation.

    The people most affected by climate change are the people least responsible for greenhouse gas emissions.

    If you’re concerned about global warming, find ways to consume fewer resources and to burn fewer fossil fuels. And lobby your government officials to make policies that benefit the environment and those most vulnerable to climate change.

    Resources

    NASA’s Climate Kids

    NASA’s Kids’ Guide to Climate Change

    National Geographic Kids Climate Change Explainer

    Take Action: Young Voices for the Planet

    Science Moms

  • Why do flowers bloom? How do flowers grow? Why are flowers different colors? Why do people find flowers beautiful? How are seeds made? Why do plants grow from seeds? Why do we put seeds in the garden? We’re answering your questions about seeds and flowers with garden writer Charlie Nardozzi and Hannes Dempewolf from The Crop Trust. Find more answers to plant questions in two of our older episodes: How Do Big Plants Grow From Such Small Seeds? and Are Seeds Alive?

    Download our learning guides: PDF | Google Slide | Transcript

    New seeds are made through pollination, plant reproduction. Pollen makes its way to the ovary of a flower in various ways. Sometimes it is spread from one flower to another by a pollinator, like a bee or hummingbird. Some flowers are called “perfect”, meaning they can reproduce with their own pollen–not the pollen from another plant. But they still need a way for their own pollen to drop onto their egg. A gentle gust of wind, or the jostling of the plant by a gardener's hand can do the trick.

    The flower will create the seed and then the flower structure will fade, leaving behind a seed. Sometimes it’s in a pod, sometimes it’s in a fruit or other structure to protect it.

    Seeds are alive, but dormant. They contain all the nutrients needed to make a new plant. That seed will wait for the right conditions to germinate and create a new plant. Some seeds only need a little moisture to germinate, others need to be submerged in water. There are many different kinds of seeds and they have different necessary conditions.

    Flowers can be many different colors. They use those colors to attract pollinators. Those colors are created by pigments, natural colorings, in the plants.

    Some plants only flower once per year, others can bloom multiple times. Some plants flower in spring, others in summer, and some in fall.

    There is a lot of diversity in plants and the way they reproduce. That benefits all of us because if some plants aren’t thriving in certain conditions, other plants may do better.

    Resources

    Seed sprouting experiment

    Window gardening for kids

    Webinar: Gardening with Kids

  • Why are some people right-handed and some are left-handed? And what’s up with some people being ambidextrous (equally good with both hands)? Why, in the past, did some people try to make left-handed people use their right hands? We talk with Chris McManus, professor and author of the book Right Hand, Left Hand: The Origins of Asymmetry in Brains, Bodies, Atoms, and Cultures. We’ll even find out how common left-handedness (or left-pawedness) is in other animals!

    Download our learning guides: PDF | Google Slide | Transcript

    Why do we prefer one hand over the other? McManus says it probably pays to specialize. It’s better to do something with one hand over and over and get really good at it, as opposed to doing it sometimes with one hand and sometimes with the other. For example, it takes years to develop your handwriting, so it would take twice as long to develop good handwriting with both hands!

    How do we pick which hand? We chose the hand that feels more normal to us, and then we practice with that hand. Try a simple experiment: bring your hands together quickly and entwine your fingers like you’re holding hands with yourself. Which thumb do you have on top? Now switch which thumb is on top. It probably feels a bit wrong.

    90 percent of people use their right hand more. Our brain is asymmetrical (different on the right and left sides), and most of us use the left half of our brain to talk. Our heart is also on the left side of our body for most humans and vertebrates.

    There must be an advantage to being left-handed or we wouldn’t have left-handed people, but no one is sure exactly what that advantage is.

    What about people who say they’re ambidextrous? McManus believes there’s no such thing. He says people who say they’re ambidextrous are generally good at different things with each hand, but aren’t actually equally good at everything with both hands. McManus calls these people mixed-handers.

    Many animals also have handedness. But while right-handedness is dominant i people, animals tend to split down the middle. (So, for example, half of cats are right-handed, half are left-handed. Same goes for dogs and mice etc.

    in the 19th century, when people wrote with pens dipped in inkwells, writing with your left hand was messy business, as left hands would smear ink across the page. But as people have shifted to mostly typing, the hand you write with matters less.

    For every five left-handed boys, there are only four left-handed girls, and scientists have no idea why.

  • Why do pigs snort? And why do we call their snorts “oink” in English? We’re taking our exploration of animal noises in two directions today. First we’ll learn about why we use different words to describe animal noises, depending on what language we’re speaking. And then we’ll examine what animals are actually saying when they oink or tweet or moo! Our guests are linguist and author Arika Okrent and bioacoustic researcher Elodie Briefer, of the University of Copenhagen. Other questions we tackle in this episode: Do cows make different amounts of “moos” to say different words? Why do ducks make loud noises? Why do roosters cockadoodle-do in the morning? PLUS, so many kids sent us animal noises in different languages and we’ll hear them all!

    Download our learning guides: PDF | Google Slide | Transcript

    Bioacoustics is the study of sounds made in nature. Scientists like Elodie Briefer study how animals make sounds and what information we can find in those sounds. Scientists will record sounds and use computers to measure and analyze what they hear and use observational skills to help determine what the sounds might mean.

    Animals speak in emotion, not in words. Pigs have contact calls as well as positive and negative calls. Researchers have found that pigs will make longer calls when they are unhappy. Scientists and animal welfare advocates hope to use this information to eventually develop an app that farmers can use to improve animals’ lives on farms.

    With words like moo, oink and cockadoodle-do, we are giving a name to a sound. But we’re not just trying to mimic the sound. Most of us can make the sound of a pig snort but we need words like oink because we don’t want to stop using our language to make a pig snort in the middle of a conversation.

    Human voices are capable of millions of sounds but a language only uses a subset of those sounds. Our animal noise words will use the sounds available in our individual languages.

    Words that sound like the sound they are describing are called onomatopoeia.

    An animal has to have some cultural importance for a language to create a word for its call. That’s why we don’t have words in English for the noise a camel or a sloth would make. In Turkish there is no word for a pig call because that culture doesn’t keep pigs on farms.

  • We’re bringing back an episode from the archives, all about the moon: Why does the moon change shape? How much does it weigh? What color is it? Why does the Earth only have one moon? Why does it have holes? Where does it go when we can't see it? Why do we sometimes see it in the daytime? And why does the moon look like it's following you when you're in the car? Answers to your moon questions with John O'Meara, chief scientist at the W.M. Keck Observatory.


    Download our learning guides: PDF | Google Slide | Transcript | Coloring Page

    We can see the moon during the day for the same reason we see the moon at night. The surface of the moon is reflecting the sun's light into our eyes. But we don't see the moon all the time during the day, and that's because of where the moon might be in the sky. There are times where the moon is on the other side of the earth so we can’t see it. We see the moon in the sky when it’s in the right spot and it’s reflecting enough light to be brighter than the background of the sky.

    The moon is a satellite. A satellite is something that moves or rotates around a planet, the earth in this case. The moon is 239,000 miles away. That's far, but it's way closer than any of the other stars or planets you can see in the night sky. That's why the moon looks so big compared to other celestial objects even though the stars are actually much bigger.

    The moon weighs 100,000,000,000,000,000,000,000 pounds. That’s a lot! But it’s such a big number it’s hard to imagine how much that weighs. Instead, think about how much the moon weighs compared to the Earth. It turns out that the moon is about 1% percent the mass of the earth. That’s a lot!

    When you’re in a car and it feels like the moon is following you, what you’re actually seeing is an optical illusion. The moon is very far away, compared to anything else you see when you're driving — like the telephone poles that appear to fly past your car as you're going down a highway. But the moon is so far away that its size and shape in the sky doesn’t change, so it feels like the moon is following you.

  • The invasion of Ukraine has been the top story in the news for the last few weeks, and kids around the world are asking questions about what is happening and what it means for them. In this episode we ask Erin Hutchinson, Assistant Professor of Russian History at the University of Colorado Boulder, to help us understand the history behind this conflict. Adults: we don’t go into detail about what war looks like on the ground, but we acknowledge war is a scary topic. You may want to preview this episode ahead of time to make sure it's right for your kids.

    Download our learning guides: PDF | Google Slide | Transcript

    We have collected some resources for parents/caregivers about how to talk to kids about war and ways families can help.

    How to talk to kids about war

    Meet the Helpers

    Common Sense Media

    News Sources for Kids from Common Sense Media

    NAMLE Parent’s Guide to Media Literacy

    Ways To Help

    Save the Children

    UNICEF

    Eurasia Foundation

    Donations for refugees in Moldova

  • Violet, 5, wants to know: what was life like before refrigerators? And Ellinor, 6, asks: how did they make ice in the old times? In this episode, we learn about the history of ice harvesting and the industry that built up around it, where ice cut from lakes in New England was shipped to as far away as India and the Caribbean. We hear more about this history from Gavin Weightman, author of The Frozen Water Trade. And we visit Rockywold-Deephaven Camps in New Hampshire, where ice is still harvested each winter from Squam Lake and used to keep old fashioned ice boxes at the camp cool all summer long.


    Download our learning guides: PDF | Google Slide | Transcript

    Before refrigeration, people stored food in a lot of different ways. Food would be smoked, dried, salted, fermented or pickled. It would also be kept in root cellars or pits underground.

    Wealthy people who lived in cold climates were more likely to have an ice pit or later an ice house where they would keep ice for use in warm months.

    In the 1800s, a Massachusetts man named Frederic Tudor thought he could get wealthy by shipping ice to warmer climates. After trying and failing many times, he finally succeeded in convincing people that there was a market for ice and wound up shipping ice around the world, as far away as India. The ice was kept cold by insulating it with straw and sawdust and stored in warehouses until it was time to be used.

    People cut ice from lakes using hand saws. Eventually they started using horse drawn machinery to cut ice, but it was still hard and dangerous work.

    People in cities also became accustomed to ice as an everyday necessity, and eventually, naturally harvested ice was eventually replaced by ice made in factories. In cities, “ice men” would deliver ice to butchers and fishmongers, and to individual houses, where people would use them in their ice boxes.

    Ice boxes were wooden or metal chests with a compartment in the top where a block of ice would be placed. Cold air falls and cools the food below it. Ice boxes needed more ice every day or two.

    The electric refrigerator was invented in the early 1900s and became popular by 1940.

    Resources

    Ice Harvesting Video

  • Why is the heart a symbol of love? Why do people draw hearts when they love someone? Why do we draw hearts the way we do when they're nothing like the hearts inside of your body? And do we need a heart to love or does the brain do it? We’re learning all about hearts and symbolism with Thomas and Stephen Amidon, authors of The Sublime Engine: A Biography of the Human Heart.

    Download our learning guides: PDF | Google Slide | Transcript

    No one really knows where the heart symbol comes from, but there are theories. One is that the heart shape comes from the shape of the leaves of a now-extinct plant called silphium, which was considered a key component of a love potion in the time of the Romans. Another theory is that St. Valentine used the symbol when arranging secret marriages. Another is that it was simply a guess of what the human heart looked like.

    Love and other emotions are actually regulated in the brain, not the heart. Specifically, a part of the brain called the amygdala.

    People might partly associate the heart with strong emotions like love because when we get excited to see someone, our heart sometimes beats faster, and we notice our heartbeat. We aren’t really aware of what’s happening in our brain.

    The human heart pumps blood to all parts of your body. The heart beats once a second. If you live to the age of 70, your heart will have beat about 2 billion times!

    Resources

    How the heart actually pumps blood - TEDEd

    Your Hardworking Heart and Spectacular Circulatory System by Paul Mason

    Heart and Circulatory System Activities

  • The U.S. Mint is producing a new series of quarters featuring American women. The first one, featuring poet Maya Angelou, has just been released. We're learning about coins are made and how images are chosen for money around the world. The US has a law preventing any living person from appearing on its money. Kenya has a new rule preventing any individual people on their money at all. Meanwhile, many countries with kings or queens have those leaders on their money while they’re still in power. Questions we tackle in this episode: How are coins made and how do they get their logos? How are presidents chosen for coins? Why does Lincoln have his shoulder in the picture while other presidents don’t? Why are coins different sizes? What are coins made of? We learn more from Rodney Gillis of the American Numismatic Association and Leigh Gordon of the Royal Australian Mint.

    Download our learning guides: PDF | Google Slide | Transcript

    Some people like learning about coins so much they collect them! A coin collector is called a numistmatist! Numismatics is the study or collection of coins, paper currency, and medals.

    The U.S. Mint makes coins for the United States. There are four facilities in the US where our coins are made: San Francisco, Denver, Philadelphia, and West Point, New York

    A new image on a coin requires approval from Congress.

    Australian coins feature kangaroos, koalas and native plants.

    U.S. Coins mostly feature former presidents, but some non-presidents have appeared on coins including Susan B. Anthony, Sacagawea and Ben Franklin. The reverse side of quarters changes frequently. There are quarters for every state. Over the next four years the U.S. Mint is releasing quarters featuring 20 notable American women.

    US law says no living person can be pictured on our money.

    Today, the smallest US coin is a dime. But there used to be something called a trime! It was a tiny 3-cent coin and it was so small and thin that it often got bent in people’s pockets.

    Resources

    Coins for A’s

    U.S. Mint Collector’s Corner

    How Coins Are Made

  • What causes wind? How is wind created? Why does the wind blow in different ways? How does the wind start blowing and what makes it stop? Why is it windy by the ocean? Why does it get windy when the weather is changing? How is it you can you feel and hear the wind but not see it? Why is the wind sometimes strong and sometimes cold? Answers to all of your wind questions with National Weather Service Meteorologist Rebecca Duell.

    Download our learning guides: PDF | Google Slide | Transcript

    Wind is just the air around us moving. The atmosphere always wants to be in balance. Some areas of the atmosphere have more air pressure than others. When there’s a pressure imbalance, the higher pressure air moves to fill a vacuum left by lower pressure air.

    The wind starts blowing when that balance is off - when one area is heated more than another area. That heat comes from the sun. Warm air will rise and cold air will sink. When one area is heated that warm air will start to rise. Air at the surface will be rushing to fill that area where the air is rising.

    Wind near the ocean is called a sea breeze. The land is absorbing more heat from the sun than the ocean water absorbs. As the less dense warm air over the land starts to rise and the cooler, the more dense air over the ocean rushes in to fill the space. If there’s enough moisture in the air when it rises, it will cause rains, which is why you often get afternoon rain and thunderstorms in places like Florida.

    The wind can be hot or cold depending on where that air is coming from. The northern winds will be colder, winds from the south will be warmer. (In the northern hemisphere. It’s opposite in the southern hemisphere.)

    Related Episodes

    What’s What With The Weather?

    How Do Meteorologists Predict the Weather?

    Experiment

    One way to see the wind is to put some steam or smoke into the air. Which way is it blowing? Be sure to have an adult help you! Or you can look at a smokestack or chimney. Which way is the smoke blowing? Are there other ways you can see the wind?