Every What If? Lab

349 to explore · page 5 of 8

• Watch What If? Lab What if plants glowed in the dark? Some living things make their own light: fireflies, a few kinds of mushrooms, and many animals in the deep sea. It's called bioluminescence. Garden plants don't glow, but scientists have now made a few plants that do. Imagine a world of glowing plants: how bright would it be, and what might it change?
• Watch Try it What If? Lab What if plants had more carbon dioxide? Leaves build sugar out of carbon dioxide from the air, using the energy in light. Some greenhouse growers add extra carbon dioxide on purpose. Raise the carbon dioxide around a model leaf from today's level to more than double and see how much faster it makes sugar, and why it soon stops helping as much.
• Watch Try it What If? Lab What if plants received less light? Green leaves use light to turn water and carbon dioxide into sugar, their food. In our model leaf, cut the light to a quarter and watch how much sugar it still makes, then find out how some forest trees manage to live in deep shade.
• Watch What If? Lab What if Pluto were still called a planet? Pluto was called our ninth planet for 76 years. Then astronomers found many similar icy worlds beyond Neptune, and in 2006 the International Astronomical Union wrote a definition of 'planet' that made Pluto a dwarf planet. What if Pluto had kept its old title? Explore how a planet is defined, the other dwarf planets, and why science sometimes changes its words.
• Watch What If? Lab What if pollution disappeared from cities? Vehicles, factories and other sources can put pollution into city air. Since 1970, EPA says total emissions of six main air pollutants in the United States have dropped by 78 percent, and cities such as Beijing have cut their pollution too. Imagine city air with no pollution at all, and follow what might change.
• Watch What If? Lab What if popcorn did not pop? A popcorn kernel holds a tiny drop of water inside a hard shell. When it is heated, the water turns to steam, the pressure builds, and the shell bursts. Imagine popcorn that didn't pop, and follow the clues: the water inside, the steam pressure and other grains that pop.
• Watch Try it What If? Lab What if pulleys had friction? A pulley system with four ropes can make a heavy crate feel four times lighter, but only in a perfect world with no friction. Turn friction up in Olly's model and see how much harder you have to pull, and where the extra work goes.
• Watch Try it What If? Lab What if rabbits had more babies? Rabbits are famous for having lots of babies. So if every rabbit in a meadow had babies twice as fast, you would expect a meadow full of rabbits. In our rabbit and fox model, something surprising happens instead: the extra rabbits mostly end up feeding more foxes.
• Watch Try it What If? Lab What if rain grew more slowly than water vapor? Warm air can hold about 7 percent more water vapor for each degree. Climate models find that rain around the world grows only about 1 to 3 percent per degree. In this lab, warm the world by 2 °C and compare the two rates: if rain lags behind, water spends longer in the air.
• Watch What If? Lab What if rainbows appeared at night? A rainbow appears when light shines into drops of water from behind you. Sunlight usually does the job, but bright moonlight can too, making a faint “moonbow”. Explore moonbows, why the light must be behind you, and the ghostly white fog bow.
• Watch What If? Lab What if rivers made electricity everywhere? Falling and flowing water can spin a turbine, and a turbine can spin a generator to make electricity. That's hydropower, one of the oldest ways people have used energy. Imagine every river making electricity, then discover how dams work, why fish need a way past them, and how small water wheels can power a single farm.
• Watch What If? Lab What if robots did all the chores? Millions of robot vacuums already clean floors, but folding a T-shirt is still very hard for a robot. Explore what household robots can do today, why messy, changing jobs like laundry are so tricky, and what robots doing more chores could mean for people.
• Watch What If? Lab What if rubber were not stretchy? Rubber stretches because its molecules are long, tangled chains. Pull, and they straighten out. Let go, and they curl back into a tangle. Imagine rubber that would not stretch and follow what might change for tires, balloons and rubber bands.
• Watch What If? Lab What if salt did not melt ice? Salt water freezes at a lower temperature than plain water. That's why salt melts icy roads and why salty ice can freeze ice cream. Imagine salt that did nothing to ice and follow what might change.
• Watch What If? Lab What if Saturn’s rings vanished? Saturn's rings are billions of icy chunks, and some of that ice is slowly raining down onto the planet. NASA scientists estimate the rings could be gone in less than 300 million years. Explore what the rings are, how they fade, how they already seem to vanish from Earth's view, and what Saturn would be like without them.
• Watch Try it What If? Lab What if sea levels rose? When the sea rises, the water's edge moves inland. How far depends on the land: on a steep cliff it barely moves, but on a flat, gentle coast a rise of 76 centimeters in our model moves the shore about 760 meters.
• Watch What If? Lab What if sea turtles lost their way? Sea turtles cross oceans and return to the coast where they hatched, using Earth's magnetic field like a map. Baby turtles find the sea by heading for the brightest horizon. Imagine them losing their way: follow magnetic maps, bright beach lights, and how people help hatchlings.
• Watch What If? Lab What if seeds could not travel? Seeds ride the wind, float on water, hide in fruit that animals eat, and cling to fur and socks. What if every seed simply dropped under its parent plant? Explore crowded seedlings, wind and animal helpers, and the burrs that gave people an idea.
• Watch What If? Lab What if shadows had colors? A shadow is a place where an object blocks the light. With one lamp, the shadow looks dark. But shine a red and a green light on one object and you get two shadows, one green and one red, because each shadow is lit by the light that is not blocked. Add a blue light and the shadows turn yellow, cyan and magenta.
• Watch What If? Lab What if sharks disappeared? Sharks catch and eat other sea animals, and just having them around changes where those animals go. Follow what scientists have found in Australia's Shark Bay seagrass meadows and on coral reefs, where the evidence is still debated, and how some shark populations are recovering.
• Watch What If? Lab What if skyscrapers could not sway? Tall buildings sway a little in strong winds and earthquakes, and some even hang giant weights inside to calm the motion. Imagine a skyscraper that couldn't sway at all, and follow the clues: the push of the wind, giant swinging weights, and bending without breaking.
• Watch What If? Lab What if snow fell in the desert? A desert is a dry place, not always a hot one. Clear desert skies let heat escape at night, some deserts are icy cold, and snow has even dusted sand dunes in the Sahara. Explore what happens when snow falls in a desert, and how desert plants cope with the cold.
• Watch What If? Lab What if snow were black? Clean snow is white because it reflects most of the sunlight that hits it, which helps it stay cold and frozen. Dark things soak up sunlight and warm up. In some mountains, dust blowing onto snow already makes it melt weeks earlier. Imagine snow that was black, and find out why color matters so much.
• Watch What If? Lab What if soap did not exist? Water on its own slides right off greasy hands. Soap is different: each soap molecule has one end that holds on to grease and another end that holds on to water, so the grease, dirt and germs rinse away. Imagine a world without soap and follow what might change.
• Watch Try it What If? Lab What if solar panels became much more efficient? Efficiency is the share of sunlight a panel turns into electricity. Raise it from 20 to 30 percent in our model and the same panel, in the same sunshine, makes half as much electricity again, so a smaller roof could do the same job.
• Watch Try it What If? Lab What if solar panels received less sunlight? A solar panel turns sunlight into electricity, so the more sunshine reaches it, the more power it makes. In our model, one rooftop panel on a clear summer day makes about 310 watts at noon. When clouds let through only a quarter of the direct sunshine, it makes only a quarter as much. Then find out why real panels can do better than our model on cloudy days.
• Watch Try it What If? Lab What if solar panels were near the equator? On 21 December in London, the noon Sun is only about 15° above the horizon, and it is up for less than 8 hours. In our model, a rooftop panel there makes about 0.64 kilowatt-hours that day. Move the same panel to the equator and the Sun climbs to about 67° and shines for 12 hours: the panel makes about 2.34, more than three and a half times as much.
• Watch Try it What If? Lab What if sound couldn’t travel through air? Sound is a push passed from particle to particle. In air it travels about 343 meters every second. Take the air away, as in empty space, and there is nothing to pass the push along, so a clap makes no sound at all. Water and steel still carry it, and much faster.
• Watch Try it What If? Lab What if sound traveled through water? Sound does travel through water, and it goes more than four times faster than through air. Send the same sound 1,000 meters through air and then through water in our model, then find out how whale songs carry so far in the real ocean.
• Watch What If? Lab What if sugar would not dissolve? When sugar dissolves, it doesn't disappear. Its tiny molecules spread out among the water molecules, so you can't see them anymore. Warm water holds more sugar, and the sugar can even grow back into crystals. Imagine sugar that would not dissolve and follow what might change.
• Watch What If? Lab What if telescopes found planets around every star? Astronomers have confirmed thousands of planets around other stars, called exoplanets: 6,451 in NASA's Exoplanet Archive in October 2026. Most were found by watching a star dim slightly as a planet passed in front. Imagine planets around every star, meet some worlds a bit like Earth, and see how a tiny dip in starlight reveals a planet.
• Watch What If? Lab What if the air were full of dust? Every year, winds lift millions of tons of dust from the Sahara Desert and carry it across the Atlantic Ocean. Dust and other tiny particles in the air can color sunsets red, make the sky hazy and get into our lungs. Imagine air that was always full of dust, and find out why clean air matters.
• Watch What If? Lab What if the continents joined together again? Earth's outer shell is broken into plates that move a few centimeters a year. Long ago the continents were joined in one supercontinent called Pangaea, which USGS says began to break up about 225 to 200 million years ago. Imagine the continents joining together again, and follow what might change for land, climate and animals.
• Watch What If? Lab What if the continents stopped moving? Earth's outer shell is broken into giant plates that creep along just a few centimeters a year. Where they meet, they build mountains and cause earthquakes and volcanoes. Imagine the plates stopped: rain, ice and wind would keep wearing the land down, but nothing would push new mountains up.
• Watch What If? Lab What if the ground were made of limestone? Limestone is a rock that rainwater slowly dissolves. Over thousands of years, water seeping through it carves caves, opens sinkholes and bubbles back up as springs. About a fifth of the land in the United States is already this kind of landscape, called karst. Imagine the ground everywhere were limestone, and find out what would happen to the rain.
• Watch Try it What If? Lab What if the Moon and Sun lined up? The Moon and the Sun both stretch Earth's oceans into tides. When they pull at right angles, at a quarter moon, their stretches partly cancel. In our model, lining them up at new moon makes the tides about 2.7 times as strong: these big tides are called spring tides, and they have nothing to do with the season.
• Watch What If? Lab What if the Moon had air? The Moon has almost no air, so its sky is always black and it has no weather. Scientists have found that the Moon once had an atmosphere, billions of years ago, but it was lost to space or became part of the ground. Explore what air would change, and why small worlds lose theirs.
• Watch What If? Lab What if the Moon had no craters? The Moon is covered with craters made by space rocks crashing into it. With no wind, rain or flowing water, the Moon keeps its craters for billions of years, while Earth wipes most of its craters away. Imagine a smooth Moon, and discover how scientists count craters to tell how old a surface is.
• Watch What If? Lab What if the Moon turned red? During a total lunar eclipse, Earth moves exactly between the Sun and the Moon, and Earth's shadow covers the full Moon. The Moon does not go black. NASA explains that sunlight passing through Earth's air loses its blue light and bends toward the Moon, so the Moon glows red or orange, lit by all of Earth's sunrises and sunsets at once.
• Watch Try it What If? Lab What if the Moon were closer? The Moon's tides depend very strongly on distance. Bring the Moon to half its distance in our model and its stretching of the oceans becomes 2 × 2 × 2 = 8 times stronger, while each trip around Earth takes only about ten days.
• Watch Try it What If? Lab What if the oceans became warmer? Water expands a little when it warms. The ocean is so deep and wide that this small stretch adds up: in our model, warming the top 700 meters by 2 °C raises the sea about 28 centimeters, with no ice melting at all.
• Watch What If? Lab What if the Sahara turned green? Thousands of years ago, the Sahara Desert was a land of grass, wetlands and lakes, where cave paintings show hippos in watering holes. A slow wobble of Earth on its axis brought stronger monsoon rains. Find out why the Sahara was green, why it dried, and what might change if it turned green again.
• Watch What If? Lab What if the sea were as clear as glass? Sunlight fades as it goes deeper into the sea, and below about 200 meters there is hardly any. Tiny drifting plants and bits of mud also change how green, blue or murky the water looks. Imagine the sea perfectly clear, then follow how deep light would go, what it would mean for seaweed forests, and what gives the sea its colors.
• Watch What If? Lab What if the sea were not salty? Rain and rivers wash tiny bits of salt out of rocks and carry them to the sea, where they build up. Imagine a sea with no salt: most sea creatures are built for salty water, sea ice would form differently, and deep ocean currents would lose one of their pushes.
• Watch Try it What If? Lab What if the second hill were taller than the first? A roller coaster gets all its energy from its first big hill, and friction slowly uses some up along the way. In our model, a car that starts 40 meters up easily gets over a 25-meter second hill. Make that hill 45 meters, taller than the start, and the car can never reach the top: it rolls back.
• Watch What If? Lab What if the stars were much closer? Every star is a sun, but even the nearest one is more than four light-years away, so stars look like faint points. Bring them closer and they would shine much more brightly. In real crowded star clusters, the sky would be full of bright stars, but stars that close may make it hard for planets to form.
• Watch Try it What If? Lab What if the Sun disappeared? The Sun cannot vanish, and it will keep shining for billions of years. But imagining it gone answers a real question: what keeps Earth going round? Switch off the Sun's pull in our model and Earth stops curving and travels on in a straight line.
• Watch What If? Lab What if the Sun had no sunspots? Sunspots are darker, cooler patches on the Sun made by strong magnetic fields, and their numbers rise and fall about every 11 years. Imagine a Sun with none: what would happen to its light, to solar storms and to the auroras they bring? Once, for about 70 years, the real Sun came close.