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What If? Lab What if Mars had oceans again? Mars is a cold, dusty desert today, but rovers have found dry riverbeds, deltas and an ancient lake. Its air is now so thin that liquid water can't last on the surface. Imagine a blue Mars, find out what it would need, and see a possible clue to past life that NASA's Perseverance rover has found.
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.
What If? Lab What if an ocean food web changed? Antarctic krill are small shrimp-like animals, but they feed a huge number of bigger ones. Take krill out of our model's Southern Ocean food web and all seven other species are affected: every animal in it loses all its food, from silverfish to orcas.
What If? Lab What if there were no ocean currents? Ocean currents are like rivers in the sea. They carry warm water away from the equator and cold water away from the poles, and some lift food-rich water up from the deep. Imagine them stopping: follow the Gulf Stream, warm and cold coasts, and the rich fishing waters fed by upwelling.
What If? Lab What if orcas left the Southern Ocean? Orcas are apex predators: they eat at the top of the food web. Take them out of our model's Southern Ocean food web and the seals, penguins and fish they eat could become more common, which then changes the food of others. Explore the knock-on effects, and the real orcas that make long trips north.
What If? Lab What if warmer seas changed ocean life? When seawater gets too warm, corals can lose the tiny algae that feed them and turn white. Fish and shellfish move toward cooler water, and a long ocean heatwave can leave whole food webs short of food. Explore what scientists have seen, and what they still study about storms.
What If? Lab What if whales returned to every ocean? Hunting in the last century took away most of the world's great whales, and since a 1985 ban on commercial whaling many are growing in number again. Whale poop feeds the tiny drifting plants at the base of the ocean food web, and whale bodies carry carbon to the deep sea. Imagine whales back in every ocean and follow what they might do.
What If? Lab What if the whole Earth were covered by ocean? Water soaks up a lot of heat before it gets hot, and gives it back slowly. Turn a patch of damp ground into ocean in our model and watch the gap between day and night temperatures shrink, then see how the sea already keeps coastal towns mild.
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.
What If? Lab What if all the sea ice melted? Sea ice floats, so it is already pushing aside about as much water as it will make when it melts, like an ice cube in a glass. In our model, melting all the Arctic's springtime sea ice raises the sea by only about 2 millimeters. The same ice melting on land would raise it about 7 centimeters.
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.
What If? Lab What if cities floated on the sea? Floating buildings already exist: in Rotterdam, in the Netherlands, a three-story office floats in a harbor on concrete pontoons. Designers have also planned a floating neighborhood off Busan, South Korea, for up to 12,000 people. But a floating city would need to stay afloat, cope with waves and storms, and find fresh water in the middle of salty sea. Explore each challenge.
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.
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.
What If? Lab What if Earth had no Moon? The Moon's pull stretches Earth's oceans and gives us most of our tides. Take the Moon away in our tide model and see what is left: the Sun still makes tides, but they are less than half as big as the Moon's.
What If? Lab What if waves had no wind? Most ocean waves are made by wind blowing over the water. So what if the wind stopped everywhere? New waves would stop forming, but swells from earlier storms could keep rolling in for a while. And the tide would still come in and go out, because tides are made by the pull of the Moon and the Sun, not by wind.
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.
What If? Lab What if there were no plastic? Plastic is light, cheap and lasts a long time, so it is everywhere: in toys, bottles, phones, cars and hospitals. Those same things make it hard to clean up when it ends up in the ocean. Imagine a world without plastic, then meet the older materials and the new plant-based plastics people are designing.
What If? Lab What if you visited an icy moon? Jupiter's moon Europa and Saturn's moon Enceladus are covered in ice, but scientists think salty oceans lie underneath. The squeezing pull of their giant planets keeps the insides warm. Imagine walking on the ice, peeking at the ocean below and joining the search for places where life could exist.
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.
What If? Lab What if waves came from a faraway storm? Some waves are made by wind nearby: short, choppy and close together. Others are swells that have traveled thousands of kilometers from a distant storm: long, smooth and far apart. In our model, waves 1.5 meters high arriving every 14 seconds carry about 2.3 times the power of equally tall waves arriving every 6 seconds, and wear a sandy island away much faster.
What If? Lab What if you could dive to the deepest trench? The Challenger Deep, at the bottom of the Mariana Trench, is about 11 kilometers down: deeper than Mount Everest is tall. Imagine diving there. Discover how strong the water's squeeze becomes, what lives in the dark, and the explorers who have already made the trip.
What If? Lab What if glaciers melted? Glaciers are huge, slow-moving masses of ice on land. When land ice melts, its water runs into the ocean and raises the sea. In our model, melting every mountain glacier on Earth would lift the sea by about 40 centimeters; scientists' best estimate is a little less, about 32.
What If? Lab What if an ice age came back? About 20,000 years ago, ice sheets more than 3,000 meters thick covered much of North America, and the sea was about 125 meters lower than today. Ice ages come and go over tens of thousands of years as Earth's orbit and tilt slowly change. Imagine an ice age returning, and follow what might change.
What If? Lab What if a beach lost its dune plants? Grasses such as marram grass and sea oats grow on sand dunes, and their spreading roots help hold the sand in place. In our coast model, taking away all the plant cover makes ordinary waves wear a sandy shore about 1.7 times faster.
What If? Lab What if a coast were made of hard rock? Waves wear coasts away, but not every coast wears at the same speed. In our model, a bare sandy island facing ordinary waves keeps about 72 percent of its land after 50 model years. Make the same island of hard rock and it keeps about 99 percent. That is why hard rock is often left sticking out to sea as headlands.
What If? Lab What if cold wind blew over a warm lake? In late fall and winter, the Great Lakes are often much warmer than the freezing air that often blows in from Canada. As cold wind crosses the open water, it picks up warmth and moisture, rises and builds narrow bands of clouds that can drop 2 to 3 inches of snow an hour, while a town a mile or two away stays sunny. This thought experiment follows the air across the lake.
What If? Lab What if mangroves lined every tropical coast? Mangroves are trees that grow where land meets the sea in warm places, standing on tangled roots. Their roots calm waves, give young fish a safe place to grow, and hold lots of carbon in the mud. Imagine mangroves along every tropical coast and follow three paths: calmer waves, fish nurseries and stored carbon, then find out where mangroves can and can't grow.
What If? Lab What if your skin could make food from sunlight? Plants catch sunlight and turn it into food, a process called photosynthesis. Imagine if your skin could do the same. Would you be able to skip meals? We'll compare how much energy your body needs with how much sunshine could give, and meet a real sea slug that keeps borrowed plant parts working inside its body.
What If? Lab What if June were winter? Earth's two halves take turns leaning toward the Sun, so they have opposite seasons. In our sunlight model, on June 21 London gets 16.4 hours of daylight and a high Sun, while Sydney, south of the equator, gets just 9.7 hours and a low Sun: its shortest day of the year.
What If? Lab What if Earth’s tilt changed? Earth's axis leans 23.4 degrees, and that lean is what gives us seasons. Straighten Earth up in our sunlight model and the Sun climbs to the same height every noon, every day lasts 12 hours, and summer and winter disappear.
What If? Lab What if a solar panel lay flat? Sunlight gives a panel the most energy when it hits the panel straight on. In London in March, the Sun stays low in the sky, so our model panel tilted at 40° makes about 1.86 kilowatt-hours in a day. Lay it flat and the slanting light spreads out: it makes only about 1.17.
What If? Lab What if you lived on the equator? On the equator the Sun is up for about 12 hours every single day of the year, and it always climbs high at noon. In our sunlight model, moving from London to the equator on December 21 turns a 7.6-hour winter day into a 12-hour day. Near the equator, seasons are mostly about rain, not cold.
What If? Lab What if the Sun stayed low in the sky? A low Sun spreads its light thinly over more ground, and in winter it is up for fewer hours too. In our sunlight model, London's noon Sun drops from about 62 degrees in June to about 15 degrees in December, and its daily sunlight falls to about one seventh.
What If? Lab What if trees never lost their leaves? Every autumn, maples, birches and many other trees drop their broad leaves, while pines and spruces stay green. Imagine broad-leaved trees keeping their leaves all winter: what would happen to their water, to their branches in a snowstorm, and to the bright autumn colors?
What If? Lab What if every day had the same weather? Weather changes because the Sun heats some places more than others, and big bodies of warm or cold, wet or dry air keep moving around. Imagine a world where every day had the same weather: no need to check a forecast, but plants and animals that follow the seasons might be confused. Some places near the equator come surprisingly close.
What If? Lab What if we found life on another world? So far, the only life we know of is here on Earth. Scientists search for signs of life with rovers on Mars, spacecraft heading to icy moons and powerful telescopes. Find out how they look, why they test every clue so carefully, and imagine what a first discovery might be like.
What If? Lab What if Earth spun on its side like Uranus? Earth's spin axis leans 23.44 degrees, which gives us gentle seasons. Tip it all the way over to 90 degrees, like Uranus, and each pole points at the Sun in turn. In our model, a place 60 degrees north would get about four months of non-stop daylight, then about four months with no sunrise at all.
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.
What If? Lab What if you lived where the Sun never sets? North of the Arctic Circle, Earth's tilt keeps the Sun above the horizon all day and all night around midsummer: the midnight Sun. In our sunlight model, moving from 40° north to 69.5° north on June 21 turns a 14.8-hour day into 24 hours of daylight.
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.
What If? Lab What if the wind stopped blowing? Wind is air rushing from places of high pressure to places of low pressure. It carries heat, water and weather around the world, lifts seeds to new homes and has pushed sailing ships across oceans. Imagine all the air going still, and follow what might change.