Seasonal science
Summer science questions
Sunshine, sand, waves, thunderstorms, fireflies and melting ice cream. Every one is a real question from the A Million Whys books, with a short video answer.
☀️ Sunshine and sun safety
Why Use Sunscreen?
We use sunscreen because sunlight has UV rays that can burn skin and harm skin cells! Sunscreen works like a shield, blocking or absorbing some of the rays. Ask a grown-up to help you put it on, and add hats and shade too.
Why Is Sunscreen Still Useful on Cloudy Days?
A gray, cloudy day can fool you into thinking you cannot get sunburned. Clouds block some light, but a lot of the invisible UV rays can still get through. Sunscreen still protects your skin, and that is why it is smart on bright, overcast days!
Why Do Sunglasses Help on Bright Days?
On a bright day, you squint and your eyes feel tired and glary. Good sunglasses make the light dimmer and cut down glare, and the right ones also block harmful UV rays. That is why sunglasses help on bright days!
Why Wear Sunglasses in Bright Glare?
We wear sunglasses in bright glare because bright sunlight can bother and harm our eyes! Good sunglasses cut the glare and block the invisible UV light from the Sun. Never stare straight at the Sun, even with sunglasses on.
Why Must You Never Stare at the Sun?
Never stare at the Sun, because sunlight can permanently damage your eyes! It's so bright and strong that it can hurt the delicate parts at the back of your eye. Even a quick look can do harm.
Why Does the Sun Feel Stronger at Noon?
The Sun feels stronger around noon because it is at its highest point in the sky. When the Sun is high, its light takes a shorter path through the air, so less light is lost along the way. More of it reaches you, and it feels punchier!
Why Is It Cooler in the Shade than in the Sun?
Shade blocks the direct beams of the Sun. The heat energy in sunlight cannot warm you or the ground there. That is why shade feels cooler than the sunny spot beside it.
Why Do Dark Clothes Feel Hotter in the Sun than Light Ones?
Dark colors soak up most of the light that hits them. They turn that light energy into heat. Light colors bounce more light away, so they stay cooler.
Why Do You Sunburn Faster in the Mountains?
You sunburn faster in the mountains because the Sun's UV light is stronger up high! There is less air above you to block it. And snow makes it even stronger.
Why Is the Sun So Bright?
The Sun is a giant ball of hot gas, like a huge fusion lamp! Deep in its core, hydrogen slams together and becomes helium. That fusion dumps huge energy as light and heat.
🥵 Hot days
Why Do We Sweat? Your Built-In Cooling System!
Sweat is your body's natural cooling system. When you get hot, sweat comes out onto your skin from tiny sweat glands, and as the liquid evaporates into water vapor it carries heat away with it. A breeze helps the sweat evaporate faster, so you cool down more quickly. The page says your skin has about 2 to 4 million sweat glands working every day. Try running around and then standing in a breeze to test your hypothesis!
Why Does Humidity Make Hot Days Feel Hotter?
Humid air makes hot days feel hotter because it slows down your body's cooling system. When you sweat, the sweat evaporates and takes heat away from your skin. In very humid air, sweat can't evaporate as easily, so heat feels heavier!
Why Do Heat Waves Stick Around?
Heat waves stick around because of a stuck area of high pressure, sometimes called a heat dome. A high-pressure area can park over a region for days, and it keeps the hot air from moving away. Stuck weather makes sticky heat!
Why Do Mirages Shimmer on Hot Roads?
On a hot day, a faraway road can look wet and shiny even when it is completely dry. That trick is called a mirage. Hot air near the ground bends light from the sky, so you see a patch of sky that looks like water.
Why Drink Water on Hot, Humid Days?
On a hot, sticky day, your body works extra hard to stay cool. It sweats, and that sweat is mostly water that leaves your body. Drinking water replaces what you lose and helps you feel well, and that is why we drink water on hot, humid days!
Why Is Sand Too Hot to Walk on at Midday?
Sand gets too hot to walk on because it soaks up the Sun's energy! Dry sand is also not good at carrying heat downward, so the top layer gets very hot. That hot sand can burn bare skin.
Why Does a Parked Car Get So Hot with the Windows Closed?
A parked car can get dangerously hot, even on a mild day. Sunlight gets in easily. But the heat has trouble getting out! On a warm day, a closed car can heat up by twenty degrees Fahrenheit in ten minutes.
Why Does Sand Heat Up Faster than Water?
On a sunny beach, the sand feels scorching hot. But the water feels cool, even after the same hours of sun. Why do they heat up so differently?
Why Do Long Summer Days Feel Endless?
Long summer days feel endless because the Sun really does stay up longer! Earth's tilt points your half of the world toward the Sun in summer, so the Sun is above the horizon for many extra hours. That is daylight overtime!
Why Is Summer Hotter than Winter Where You Live?
Summer is hotter because of a tilt! Earth leans as it travels around the Sun. In summer, your part of the world leans toward the Sun, so light hits more directly and days last longer.
Why Do Ponds Get a Green Film in Summer?
That green film is often algae! Algae are tiny plant-like living things. With warm sun, still water, and extra nutrients, they bloom into a scum you can see.
🏖️ Beaches and waves
Why Are There Waves?
Wind pushes on the surface of the water. That push travels across the sea as a wave. The water mostly bobs up and down, but the wave's shape moves forward.
Why Do Waves Keep Coming?
Most waves are wind energy traveling through water! The water mostly just goes up and down. It's the energy that keeps rolling toward the shore.
Why Do Waves Get Bigger Near Shore?
In deep water, a wave is a long, low shape. Near shore, the bottom crowds it from below. So the wave stands taller, until it breaks.
Why Do Tide Pools Appear?
When the tide drops, some seawater stays trapped in rocky bowls. Those bowls become tiny leftover oceans. Animals wait there until the sea comes back.
Why Is Some Sand Wet Under the Dry Top?
Sand is a pile of tiny grains with tiny gaps between them. Water hides in those gaps. The sun dries the top first, but below stays damp.
Why Is Beach Sand Often Tiny?
Waves tumble rocks for years and years. Big pieces smash and rub against each other. Slowly, they wear down into tiny grains of sand.
Why Do Seashells Wash Up?
A shell is a leftover house. After the animal dies or leaves, waves carry the empty house to shore. Light, hollow shells float and roll along.
Why Is Some Sand Black?
Black sand is often tiny bits of dark volcanic rock. Or it can be heavy dark minerals left after the lighter grains wash away. The color comes from the parent rock.
Why Does Wet Sand Hold a Castle?
A little bit of water acts like glue between sand grains. Too dry, and the walls crumble. Too soupy, and they slump. Deep holes can collapse, so keep them small.
Why Does Wet Sand Look Darker than Dry Sand?
Dry sand scatters light off every grain, so it looks pale. Wet sand has a thin film of water around each grain. More light slips inside, where it gets absorbed, so the sand looks darker!
Why Can You Hear the Ocean in a Seashell?
The ocean sound in a seashell is not really the ocean! It is the quiet noise all around you, made louder by the shell's hollow space. A cup or a mug works just as well.
Why Do Ghost Crabs Dig Burrows on the Beach?
Ghost crabs dig burrows on the beach to stay cool, damp, and hidden! The hot sun can dry a crab out. So they hide deep in the sand by day and come out at night.
Why Do Sea Turtles Come Back to a Beach?
Sea turtles often return to nest on the same stretch of coast where they hatched, even decades later. A mix of smell, Earth's magnetic field, and wave clues helps guide them home. The sand holds the eggs, and the ocean holds the food.
Why Do Parrotfish Poop Sand?
Parrotfish scrape algae off rocks and coral with a strong beak. They swallow bits of limestone along with it, and grinding teeth in their throats crush it into powder. The leftover grit comes out as pale sand!
Why Do Some Beaches Have Singing Sand?
Singing sand makes sounds because layers of sand grains slide over each other together! That slipping makes a steady vibration. You hear it as a squeak, a hum, or even a boom.
Why Are Some Beaches Green?
Some beaches are green because their sand is made of tiny green crystals from volcanic rock. The crystals are a mineral called olivine. Waves leave the heavy green crystals on the beach.
🏊 Swimming and floating
Why Does Salt Help You Float?
Salt water is denser than fresh water. That means the same cup of water is heavier. Denser water pushes up harder, so floating gets easier.
Why Does a Swimming Pool Look Shallower than It Really Is?
Light bends when it leaves water and enters the air. Your brain assumes light always travels in a straight line, so it places the bottom of the pool higher than it really is. That makes the water look shallower.
Why Do Swim Goggles Keep Water Out?
Goggles are like dry rooms for your eyes. A soft gasket makes a seal against your skin, and a strap holds it tight. A good seal plus a small pocket of air keeps the pressure even, so water stays outside.
How Does a Life Jacket Keep You Afloat?
A life jacket keeps you afloat because it is filled with foam or air chambers that are lighter than water! It pushes up on your body. That force is called buoyancy.
Why Do Boats Float? The Secret of Buoyancy!
A giant steel ship can float while a small rock sinks, and it is all about pushing water aside. Water pushes up on things, and that push is called buoyancy. A boat pushes a lot of water aside, and if the upward push beats its weight, it floats. Steel ships float because the hull is a big hollow shape, so more hollow volume means more water displaced and a bigger upward push. Float a clay ball and then shape the clay into a bowl to see it yourself!
Why Do Many Sharks Keep Swimming?
Sharks breathe with gills, and gills need fresh water flowing over them. Many open-water sharks swim with their mouths slightly open, so water streams in all the time. For those sharks, swimming is how they breathe!
Why Do Some Fish Swim in Schools?
A school is a moving crowd of fish! Many eyes spot danger, and the group can twist together, so a hunter has a harder time picking just one fish. There's safety in numbers.
⛈️ Summer storms
Why Does Thunder Follow Lightning? Light Wins the Race!
Flash first, boom later! A lightning bolt is super hot and heats the air around it to hotter than the surface of the Sun. That air expands fast and explodes outward in a shock wave, which we hear as thunder. Light travels much faster than sound, so you see the flash before you hear the boom. The page shares a tip: count the seconds between them and divide by 3 to estimate the distance in kilometers.
Why Do We See Lightning Before Thunder?
Lightning and thunder start together. Light reaches your eyes almost instantly. Sound needs time to cross the air.
Why Do Thunderstorms Build So Fast?
On a hot, humid afternoon, a calm blue sky can turn into a thunderstorm in less than an hour. Hot, moist air rockets upward, and it cools as it rises. Scientists call that unstable air, and it is a storm factory.
Why Is Lightning So Bright?
A flash of lightning can light up the whole sky, even in the middle of the night. That is because the lightning channel gets incredibly hot, hotter than the surface of the Sun. Very hot air glows brightly, and lightning is a quick burst of that glow.
Why Does Lightning Zigzag?
Lightning never travels in a straight line. It zigzags and branches across the sky. That is because air is not the same everywhere, so electricity finds its way in short steps.
Why Should You Avoid Open Fields in Lightning?
An open field has no tall buildings or trees, so a person standing in it becomes one of the tallest things around. That makes you a risky target for lightning. Flat and lonely is bad lightning math.
Why Do Some Storms Make Hail the Size of Marbles?
Some thunderstorms make hail as big as marbles, or even bigger. That happens when the storm has very strong updrafts that keep ice floating high up for longer. The longer a hailstone stays up, the more icy layers it collects.
Why Do Grown-Ups Say “When Thunder Roars, Go Indoors”?
Thunder is the sound of lightning, so if you can hear thunder, lightning is close enough to be dangerous. Lightning can strike many kilometers away from the storm, even when the sky overhead looks blue. That is why the rule is: when thunder roars, go indoors.
🦟 Fireflies, crickets and mosquitoes
Why Do Fireflies Glow?
The glow is a living lantern, used as a signal. Many fireflies flash to find a mate, and some young larvae glow too, as a keep-away warning. There are over 2,000 kinds of fireflies in the world.
Why Do Fireflies Light Up?
A firefly's glow is a chemical lantern in its belly. A special reaction makes cold light with almost no heat. Each species blinks in its own pattern, like a secret code that says, I am here, and I am your kind.
Why Do Crickets Chirp?
A chirp is a cricket song. Most of the night music you hear is a male, calling to a female, or warning other males away. Only the male crickets make the loud songs.
Why Do Crickets Chirp After Sunset?
A male cricket rubs a file on one wing against a scraper on the other wing to make a chirp. The chirp is a night advertisement that says, I am here, and I am your kind. Cooler, darker hours hide him from some hunters that use sight.
Why Do Cicadas Buzz So Loud?
That loud summer roar is a male cicada calling for a mate! Ribs in his abdomen click so fast that they make a buzz that can travel across a whole yard. It takes special body parts to be that loud.
Why do some cicadas spend 13 or 17 years underground?
Periodical cicada nymphs live in the soil, feeding on sap from tree roots, for either 13 or 17 years. Then, all in the same year, they climb out, shed their skins, and become noisy adults. Emerging in huge numbers means predators can't eat them all. Scientists think prime numbers like 13 and 17 helped them avoid being on the same schedule as predators.
Why Do Mosquitoes Bite?
Not every mosquito bites people. Many sip plant juices, and only some females take a tiny blood meal, because they need extra protein to make eggs. So a bite is really an egg-making mission.
How Do Mosquitoes Find People?
Female mosquitoes find people by following several clues at once! They sense the carbon dioxide in our breath from far away. Then they use smell, warmth, and movement to get closer.
Why Do Mosquitoes Whine High While Bumblebees Buzz Low?
Mosquitoes whine high and bumblebees buzz low because of how fast their wings flap! A mosquito flaps hundreds of times each second. A bumblebee flaps more slowly, so its buzz is lower.
Why Does a Campfire Look Extra Bright at Night?
The fire did not get hotter just because the sun left. Your eyes adapted to the dim woods, so the same flames look like a spotlight. A small bright flame against black trees also makes a huge contrast.
🌅 Arctic summer and the midnight sun
What Is the Midnight Sun?
The midnight Sun is when the Sun stays above the horizon all night long in summer! It happens in places north of the Arctic Circle. Let's soak up some sunshine.
Why Do Plants Grow So Fast in the Arctic Summer?
Plants grow so fast in the Arctic summer because the midnight Sun gives them light almost around the clock! They race to grow before winter comes back. Let's watch them grow.
🍦 Summer treats
Why Does Ice Cream Melt? Frozen Water, Fat and Air!
Ice cream is frozen water, fat and air, and room heat gives its molecules energy. The solid mix turns slushy and then into soup. The page says freezer cold locks the mix in place. Time how long a scoop lasts on the table and see what you find out!
Why Does Chocolate Melt in Your Hand? Cocoa Butter Science!
Chocolate is full of special fats, and those fats melt near body heat. Your hand is about 37 degrees C, which is warm enough to turn solid chocolate soft, smooth and eventually liquid. The page says cocoa butter is designed by nature to melt near skin heat. Try holding one square in a cool spoon and another in your palm to compare.
Why Does Ice Cream in a Bag Need Salty Ice?
Ice cream in a bag needs salty ice because salt makes the ice colder than ice alone! Salty ice melts at a lower temperature, so the icy salt water gets colder than freezing. That super-cold bath chills the cream until it turns into ice cream.