110 Fun Facts About Atmosphere

What force holds Earth's atmosphere to the planet instead of letting the air drift off into space?

Gravity. The small, hot innermost planet has too weak a pull to do the same job, which is why it is left almost airless.

Oxygen, dry air's second most abundant gas, is about what percentage?

21%. Almost all of it is a by-product of photosynthesis: before living things began releasing oxygen, the air held practically none.

After the two dominant gases, which gas ranks third in dry air at nearly 1%?

Argon. Almost all of it was made inside the Earth, by the slow radioactive decay of potassium in rocks, and has been leaking out into the air ever since.

CO2 makes up roughly what percentage of dry air by volume?

0.04%. Small as that share is, burning fossil fuels had by 2024 pushed it about 50% above its level before the Industrial Revolution.

At what altitude is the Kármán line, the conventional edge of space?

100 km. The round number is a convention: Theodore von Kármán's own sums put the limit of winged flight nearer 84 km, and the US Air Force counts space as starting at 80 km.

In July 2021, whose spaceflight crossed the Kármán line days after a rival's flight had stopped short of it?

Jeff Bezos. His New Shepard capsule cleared the line nine days after Richard Branson's rocket plane peaked below it, though still high enough to count as space by the US definition.

Which is the lowest layer of the atmosphere, where nearly all weather happens?

Troposphere. It holds most of the atmosphere's mass, and its air cools with height, which is why high mountain peaks can stay snow-capped in summer.

The ozone layer sits within which layer of the atmosphere?

Stratosphere. Its air warms with height instead of cooling, so it barely churns, and airliners cruise along its calm lower edge to avoid the turbulence below.

Which layer of the atmosphere is the coldest place on Earth and where most meteors burn up?

Mesosphere. It is too high for planes and balloons and too low for satellites, so it can only be sampled by brief rocket flights and remains the least understood layer.

The International Space Station orbits within which layer of the atmosphere?

Thermosphere. Even 400 km up, enough thin air remains to drag on the station, so it slowly sinks and has to fire rocket engines every so often to climb back.

Which layer of Earth's atmosphere has no clear top and fades into space?

Exosphere. Its gas is so thin that atoms almost never collide and the fastest simply fly off, which is why some scientists count it as outer space, not atmosphere.

The troposphere, where air constantly rises and sinks, takes its name from the Greek tropos, meaning what?

Turn. The same Greek root gave us the tropics, the two lines on the globe where the Sun seems to turn back at the solstices.

Temperature rises with height in the ozone layer because ozone absorbs what?

Ultraviolet radiation. The energy ozone soaks up warms the surrounding air, and it is also why most of the Sun's most harmful rays never reach the ground.

What phenomenon makes the daytime sky look blue?

Rayleigh scattering. Air scatters short blue wavelengths far more than long red ones, so at sunset, when light crosses much more air, the blue is stripped out and red is left.

Which gas does the most to trap heat in Earth's natural greenhouse effect, about half the total?

Water vapor. Together with the other heat-trapping gases it keeps Earth's surface near 15 °C; without them the average would be a frozen −18 °C.

Who became the first skydiver to fall faster than sound, jumping from a balloon 39 km up in 2012?

Felix Baumgartner. His voice link to the ground was Joe Kittinger, the retired US Air Force colonel whose own record jump of 1960 he had come to beat.

Ozone takes its name from the Greek for 'to smell'; which kind of weather fills the air with its sharp scent?

Thunderstorms. Lightning splits molecules in the air and some of the fragments end up as ozone; the chemist who named the gas knew its smell from lightning strikes.

Ozone shields life from high above, but near the ground it is a main ingredient of which urban air pollution?

Smog. Ground-level ozone forms when sunlight cooks traffic and factory fumes on hot days, and breathing it irritates the lungs that the same gas protects from above.

Which US president signed the treaty that phased out ozone-destroying chemicals, calling it 'a monumental achievement'?

Ronald Reagan. He signed in April 1988, three weeks after the Senate had approved the deal without a single vote against it.

Which treaty to protect the ozone layer became the first in UN history ratified by every country?

The Montreal Protocol. It is working, too: a 2023 UN-backed assessment found the ozone layer on track to recover to its 1980 state within about four decades.

Which Philippine volcano's 1991 eruption threw up enough sulfur haze to cool the whole Earth?

Mount Pinatubo. Its blast lofted millions of tonnes of sulfur dioxide, and the thin haze that spread round the globe dimmed sunlight enough to cool the surface for about two years.

In 1985, British scientists reported that springtime ozone had thinned drastically above which continent?

Antarctica. Its winter is cold enough to form rare clouds high in the ozone layer, and their surfaces speed up the reactions that destroy ozone once sunlight returns in spring.

What did Paul Crutzen, Mario Molina and Sherwood Rowland jointly receive in 1995 for their work on ozone?

Nobel Prize in Chemistry. Molina and Rowland had warned in 1974 that everyday industrial gases could eat away the ozone layer, eleven years before a hole in it was actually found.

Which manufactured chemicals were the main cause of ozone depletion?

Chlorofluorocarbons. Invented as safe, non-toxic coolants for refrigerators, they drift up intact and release chlorine, and one atom of it can destroy many thousands of ozone molecules.

Oxygen atoms high in the atmosphere give the aurora its most common colour, which is what?

Green. The same atoms glow red higher up, where the air is thinner, but that light is fainter and tends to show only when the Sun is unusually active.

The word 'aurora' comes from the Roman goddess of what?

The dawn. The full name 'aurora borealis' means 'northern dawn', and it is said to date from a spectacular display that was seen right across France in 1621.

Besides Pierre Gassendi, which scientist is credited with first using the term 'aurora borealis' in the early 1600s?

Galileo Galilei. The phrase appears in a 1619 discourse on comets that was largely his work, thirty years before Gassendi printed it, yet many reference books credit the Frenchman alone.

Noctilucent clouds, the highest clouds in the atmosphere, are made of what?

Water ice crystals. So little moisture reaches that height that the ice is thought to need something to freeze onto, most likely specks of smoke left by burnt-up meteors.

Noctilucent clouds were first recorded in 1885, two years after the eruption of which volcano?

Krakatoa. Its ash painted sunsets so vividly that evening sky-watching became a craze, and whether the eruption made the clouds or simply put more eyes on the sky is still unclear.

What does 'noctilucent' roughly mean in Latin?

Night shining. The clouds float so high that the Sun, already below the horizon for anyone on the ground, still lights them up against a sky that has gone dark.

Who is usually credited with inventing the barometer in the 1640s?

Evangelista Torricelli. He argued that the weight of the air outside, not the pull of the empty space above, held up the liquid in his tube, and in the process made the first lasting vacuum.

Sea-level air pressure holds up a column about 760 mm tall of which liquid in a classic barometer?

Mercury. The column sinks as low-pressure air moves in, which is why a falling barometer has long been read as a warning of wind and storms.

Which 1979 Pacific storm set the record for the lowest sea-level air pressure ever measured, 870 hPa?

Typhoon Tip. Air Force crews flew dozens of missions into the storm to take its measurements, and at its widest it spread about 2,200 km across, the largest tropical cyclone ever observed.

Winter air pressure often tops 1,040 hPa beneath a pool of cold air named after which region?

Siberia. The Siberian High builds each winter as the frozen continent chills the air above it until it is dense and heavy, and its outflow feeds Asia's winter monsoon winds.

Half the atmosphere's mass lies below 5.6 km; which African peak alone tops that?

Kilimanjaro. Its summit stands 5,895 m above the sea, and with so much of the air left below, altitude sickness strikes many of the trekkers who walk up.

The Great Oxidation Event about 2.4 billion years ago is credited to oxygen produced by which organisms?

Cyanobacteria. Oxygen was only a waste product of their photosynthesis, and it is thought to have poisoned much of the oxygen-shunning life that had ruled the planet until then.

In which geological period did atmospheric oxygen soar above today's level as giant dragonfly-like insects took to the air?

Carboniferous. Vast swamp forests were buried and became coal faster than they could rot, which locked their carbon underground and left the oxygen they had made in the air.

The speed of sound is the basis of which number for fast aircraft?

Mach number. Sound travels at about 340 m/s (761 mph) at sea level but more slowly in the cold air where airliners cruise, so a jet up there reaches Mach 1 at a lower speed than near the ground.

In which direction do the jet streams flow?

West to east. Airlines plan routes to ride them and save fuel, which is why a flight heading east with the wind is usually quicker than the same trip flown back against it.

In which language did Wasaburo Oishi publish his 1920s jet stream discovery, leaving it largely unnoticed?

He tracked pilot balloons near Mount Fuji. Real understanding of jet streams is often credited to WWII bomber crews hitting 100 mph tailwinds.

Venus's atmosphere is 96.5% which gas?

Carbon dioxide. That thick blanket traps so much heat that the surface stays near 465 °C, which makes Venus the hottest planet in the Solar System although it is not the closest to the Sun.

Surface pressure on Venus, about 93 bar, equals the pressure at roughly what depth under water on Earth?

900 m. That crushing weight of air, together with heat of about 465 °C, is why the Soviet landers that reached the surface kept working for two hours at most.

Venus spins so slowly that one rotation outlasts its year, yet its upper atmosphere laps the planet in roughly what time?

Four days. The cloud tops race round at some 360 km/h, yet down at the surface the winds drop to a light breeze.

The average surface pressure on Mars is roughly what percentage of Earth's?

0.6%. Even that thin air comes and goes: about a quarter of it freezes onto the winter pole each year, so the pressure rises and falls with the Martian seasons.

Which moon is the only natural satellite in the Solar System with an atmosphere denser than Earth's?

Titan. Its surface air pressure is about one and a half times Earth's, thick enough for the Huygens probe to float down under a parachute and land safely in 2005.

Which substance rains from the sky and fills lakes on Saturn's largest moon?

Methane. At about −180 °C it plays the part that water plays on Earth, forming clouds, rain, rivers and seas on the only other world known to have liquid on its surface.

Edward Appleton won the 1947 Nobel Prize in Physics for using radio waves to confirm which region of the atmosphere?

The ionosphere. Its electrically charged layers bounce radio waves back to the ground, which explains how Marconi's early wireless messages could follow the curve of the Earth across the Atlantic.

Which unreactive gas is so light that, once released into the air, it eventually escapes into space for good?

Helium. Though it is the second most common element in the universe, on Earth it has to be tapped from natural gas wells, where it builds up from the slow radioactive decay of rocks.

Which astronomer posed the 'faint young Sun paradox' in 1972, asking how early Earth stayed unfrozen under a dimmer Sun?

Carl Sagan. With George Mullen he calculated that the early oceans should have been frozen solid, and proposed that traces of ammonia in the air had kept the young planet warm.

Sailors once took which blue glow, seen on a ship's mast in stormy weather, as a good omen?

St. Elmo's fire. It is named after St. Erasmus, patron saint of Mediterranean sailors, and it is real: a storm's electric field makes the air around a pointed tip glow.

Which cockpit instrument relies on the fact that air pressure falls about 12 hPa for every 100 m climbed?

Altimeter. It is really a barometer with its dial marked in feet or metres, so pilots have to reset it as the weather changes or it would show the wrong height.

The upper atmosphere can top 1,500 °C yet would feel cold; why?

Too few molecules. Each one carries a great deal of energy, which is why the reading runs so high, but so few of them would strike your skin that they could not warm it.

Mirages occur because the refractive index of air changes with which property?

Temperature. Light from the sky bends as it nears the hot air hugging a sunbaked road and curves up to your eye, so you see a shimmering patch that looks like a puddle on the tarmac.

Earth's first atmosphere is thought to have been gas left over from the Sun's birth, mostly which gas?

Hydrogen. An atmosphere that light could never have lasted, because Earth cannot hold on to hydrogen for long, and the air we know came later, largely from gases released by volcanoes.

Over which part of the globe does the troposphere reach highest, far higher than it does over the poles?

The Equator. Warm air expands, so the layer stands two to three times taller over the tropics than over the poles, and it swells in summer and shrinks again in winter.

What name is given to the well-mixed lower atmosphere, where gas ratios stay constant?

Homosphere. Turbulence keeps its gases stirred into fixed ratios; above it, in the heterosphere, they separate by weight, with the lightest on top.

Which effect of Earth's rotation makes hurricanes spin one way in the Northern Hemisphere and the other way in the Southern?

Coriolis effect. It steers storms hundreds of miles wide, but it is far too weak to decide which way a sink or toilet drains, despite the popular belief.

In which Major League Baseball city does thin, low-density air make fly balls carry the farthest?

Denver. Coors Field sits a mile above sea level, and because the city's dry air also makes baseballs livelier, the Rockies store game balls in a humidor.

Which planet's atmosphere holds the Great Red Spot, a storm watched for more than 150 years?

Jupiter. Its Great Red Spot is shrinking: in the late 1800s it could have fit three Earths side by side, and Hubble has since measured it at under half that width.

Which belt in the heart of the tropics did sailing crews dread because ships could sit stranded there for weeks?

The doldrums. Sun-heated air there rises instead of blowing across the sea, leaving so little surface wind that a sailing ship could lie becalmed for weeks.

Which gas makes up about 78% of Earth's air, almost four times the share of the oxygen people need?

Nitrogen was named azote by Antoine Lavoisier, from the Greek for 'no life', because nothing can breathe it alone. Several languages still call it that.

Which natural flash heats the air around it to about 30,000 °C and happens some 44 times a second?

Lightning heats the air so suddenly that the pressure jumps and sends out a shock wave, which is the thunder heard moments later.

At the summit of which mountain is the air pressure only about one-third of that at sea level?

Mount Everest's thin air makes most climbers carry bottled oxygen, though Reinhold Messner and Peter Habeler reached the top without it in 1978.

Dust from which desert crosses the Atlantic each year and feeds the Amazon rainforest with phosphorus?

The Sahara is the world's largest source of windblown dust, sending roughly 400 to 700 million tons into the air every year.

Which word did two Australian scientists coin in 1964 for the earthy smell of rain falling on dry ground?

Petrichor joins the Greek words for stone and ichor, the golden fluid said to run in the veins of the gods.

On Mars the daytime sky is a dusty butterscotch, but which colour glows around the setting Sun?

Blue surrounds the rising and setting Sun on Mars, the reverse of Earth, where the day is that colour and dusk turns red.

Which flow of charged particles from the Sun, racing outward at 250–750 km/s, sets off auroras near Earth's poles?

Solar wind was first measured directly in January 1959, when the Soviet Moon probe Luna 1 flew through it.

Meteorologist Edward Lorenz's rounded-off 1960s weather simulations inspired which famous idea about tiny causes?

The butterfly effect began with a seagull: Lorenz first pictured a gull stirring up a storm, then swapped in a more poetic insect and a tornado.

Which gas, about 18 parts per million of the air, gives advertising signs their reddish-orange glow?

Neon takes its name from the Greek for 'new', a name suggested by the son of its co-discoverer William Ramsay in 1898.

Which process in plants, algae and some bacteria is the main source of the oxygen in Earth's air?

Photosynthesis captures about 130 terawatts of sunlight worldwide, roughly eight times the power used by all of human civilisation.

Which term did chemist Robert Angus Smith coin in 1872 after studying the polluted air of industrial Manchester?

Acid rain forms when sulfur fumes from burning coal and oil react with moisture in the air, producing sulfuric acid that falls back to the ground.

Which weather phenomenon is really a cloud at ground level, by definition cutting visibility to under one kilometre?

Fog and mist differ only in thickness: once droplets cut visibility below 1 km it is fog, and anything clearer is merely mist.

Which word describes a region's weather pattern averaged over about 30 years, rather than conditions on any one day?

Climate comes from the ancient Greek klima, meaning 'inclination'; one freezing week is weather, not a change in the long-term pattern.

Which line-shaped clouds form when moisture in hot jet-engine exhaust freezes in the cold air at cruising altitude?

Contrails is short for 'condensation trails'; they are made mostly of ice, just like the wispy natural clouds found at the same height.

Which weather instrument did Horace Bénédict de Saussure build in 1783 using a stretched human hair as its sensor?

A hair hygrometer works because hair changes length as the air grows damper, a tiny movement that a lever magnifies onto a dial.

Which wind-speed instrument, first described by Leon Battista Alberti around 1450, usually has spinning cups today?

Anemometer comes from the Greek anemos, 'wind'; the familiar three-cup design dates from 1926 and replaced a four-cup version of 1846.

Which devices, released from at least 900 sites worldwide two or more times a day, carry radiosondes into the sky?

Weather balloons swell roughly a hundredfold as the air thins, and can climb 40 km or more before they finally burst.

Which planet has the fastest winds in the Solar System, reaching about 2,100 km/h despite its distance from the Sun?

Neptune gets only about 40% of the sunlight that reaches Uranus, yet its internal heat still powers supersonic storms.

Fishermen in which country named the Pacific's El Niño warming after the Christ child, as it arrives around Christmas?

Peru's sailors called the warm current El Niño de Navidad, the Christmas Boy, a name reported to a geographical congress in Lima in 1892.

Which Greek philosopher wrote Meteorologica around 340 BC, the oldest comprehensive treatise on weather and the skies?

Aristotle's four-book work stayed the basis of weather textbooks in the West for some 2,000 years, right up to the 17th century.

Which French thinker sent his brother-in-law up the Puy de Dôme with a barometer in 1648 to test the weight of air?

Blaise Pascal's brother-in-law Florin Périer found the mercury stood lower at the summit than in the town below, and the SI unit of pressure now carries Pascal's name.

Which English minister, who also invented soda water, isolated oxygen in 1774 and called it 'dephlogisticated air'?

Joseph Priestley gave the crew of Captain Cook's second voyage his method for making fizzy water, wrongly hoping the drink might cure scurvy.

Which towering storm cloud, often topped with a flat anvil, can produce hail, tornadoes and violent downpours?

Cumulonimbus comes from the Latin for 'heap' and 'rain cloud', and a big one can stretch from 500 m above the ground to 16 km up.

On which Hawaiian volcano has an observatory tracked the steady rise of CO2 in the air since 1958?

Mauna Loa's record also wiggles by about 6 ppm every year, as the world's land plants soak up CO2 during the growing season.

Which drilled samples hold tiny bubbles of ancient air, letting scientists read the sky's make-up 800,000 years back?

Ice cores come from holes more than 3 km deep; the air was sealed in as old snow slowly squeezed into solid ice.

Austrian physicist Victor Hess rode balloons to 5,300 m in 1912 and found which radiation growing stronger with height?

Cosmic rays kept arriving even when Hess went up during a near-total eclipse, which ruled out the Sun as their source.

Which red flashes above storm clouds, first photographed by accident in 1989, share a name with fairy-tale creatures?

Sprites can spread 50 km across, yet they went unnamed for several years after a University of Minnesota team's low-light camera caught one by chance.

Which bright spots, known to scientists as parhelia, sometimes appear on one or both sides of the Sun?

Sun dogs form when flat, six-sided plates of ice bend sunlight, and they sit about 22° to the left and right of the Sun, level with it.

Which Swiss physicist, the model for Tintin's Professor Calculus, rode a sealed balloon cabin to 15,781 m in 1931?

Auguste Piccard and his assistant landed 17 hours after take-off, having been given up for dead, with every aircraft height record beaten.

Otto von Guericke, whose air-emptied copper hemispheres defied teams of horses, was mayor of which German city?

Magdeburg gave the hemispheres their name. With the air pumped out, teams of horses could not pull them apart, yet they separated easily once a valve let air back in.

Which grim nickname do climbers give altitudes above 8,000 m, where thin air cannot sustain a person for long?

The death zone was first described in 1953 by the Swiss doctor Edouard Wyss-Dunant, who called it the lethal zone.

Above which altitude line, about 18–19 km up, does water boil at human body heat, forcing pilots into pressure suits?

The Armstrong limit is named after US Air Force general Harry Armstrong, who first recognised that saliva and tears would boil away up there.

Which English meteorologist passed out near 8,800 m on a record 1862 balloon flight later dramatised in The Aeronauts?

James Glaisher lived because co-pilot Henry Coxwell, his hands numb, climbed into the rigging to free the gas valve. The 2019 film leaves Coxwell out.

Which fruity nickname is given to the river of moist air flowing from near Hawaii to North America's Pacific coast?

Pineapple Express storms went by the plainer name 'Hawaiian Storm' until about 1980; a run of them flooded the San Francisco Bay Area in January 1952.

Which Indonesian volcano's 1815 eruption dimmed the skies enough to cause 1816's 'Year Without a Summer'?

Mount Tambora's gloom kept Mary Shelley indoors on a rain-soaked Swiss holiday in June 1816, where a ghost-story contest led her to write Frankenstein.

Which seasonal wind, known for its drenching summer rains, takes its name via Portuguese from the Arabic for 'season'?

Monsoon reached English through the Portuguese monção; the wind reverses direction between summer and winter, swapping wet months for dry ones.

Which temperature, a staple of weather forecasts, must air be cooled to before its moisture starts to condense?

Dew point is reached when relative humidity hits 100%; chill the air any further and its moisture has to turn into liquid water.

Which optical effect of the air keeps the setting Sun in view after it has truly dropped below the horizon?

Refraction lifts the Sun's image by about half a degree at the horizon, so if the air vanished at sunset the whole disc would already be out of sight.

Through which process do plants release water into the air from leaf pores called stomata?

Transpiration, with a little seepage from leaf edges, carries off 97 to 99.5% of the water a plant's roots take up.

Which Anglo-Irish chemist, whose gas law links pressure and volume, improved Otto von Guericke's air pump in the 1650s?

Robert Boyle was born at Lismore Castle, the fourteenth child of the Earl of Cork, and his book The Sceptical Chymist is seen as a cornerstone of chemistry.

Because the Moon has almost no atmosphere, what colour is its sky even at midday with the Sun shining?

Black skies are what any world without air gets, and the Moon's atmosphere is so thin that it is essentially a vacuum.

Which 13-step ranking of wind, devised by a Royal Navy officer in 1805, was first based on a frigate's sails?

The Beaufort scale swapped sails for the look of the sea in 1916, once steam power had taken over, and it was then extended to observations on land.

Which lines on a weather map, named from the Greek for 'weight', join places of equal air pressure?

Isobars are drawn from readings adjusted to sea level, and their pattern reveals the strength and direction of the wind.

Which wispy, high-altitude cloud made of ice takes its name from the Latin for a curl or tendril?

Cirrus clouds are often a sign that rain is on the way, yet all they drop themselves are thin falling streaks of ice.

Which period of fading light ends, by astronomers' definition, once the Sun sinks 18 degrees below the horizon?

Twilight exists only because of air: sunlight caught by the upper atmosphere is redirected down to light the ground after the Sun has gone.

Which weather pattern, with warm air sitting on top of cooler air, traps pollution close to the ground over cities?

An inversion flips the usual order: the lowest air is normally the warmest, because the sunlit ground heats it from below.

Which term covers the tiny solid or liquid particles hanging in the air, from sea spray and smoke to volcanic haze?

Aerosols are what clouds are built on: moisture normally condenses onto specks such as dust and salt to form each droplet.

Which dwarf planet did New Horizons find in 2015 to be wrapped in about 20 separate layers of haze?

Pluto's air is astonishingly thin: the probe measured a surface pressure roughly one hundred-thousandth of Earth's.

Which process, in which warm, less dense air rises and cooler air sinks, creates the thermals that gliders ride?

Convection also draws 'cloud streets' across the sky: in a steady wind, thermals and the puffy clouds on top of them line up in rows.

Which name do meteorologists give to a ground-level cloud of tiny ice crystals that forms under clear, frigid skies?

Diamond dust is most often seen in the polar regions and is sometimes called clear-sky precipitation, since it falls with no ordinary cloud overhead.