147 Fun Facts About The Moon

Roughly how long does the Moon take to orbit Earth once?

About 27 days, 27.3 to be exact, is one lap measured against the stars; because Earth is moving around the Sun meanwhile, the phases take two days longer, about 29.5, to come round again.

What is the name of the first human to walk on the Moon?

Neil Armstrong stepped out about 19 minutes ahead of Buzz Aldrin, and their lander carried scraps of wood and fabric from the Wright brothers' 1903 Flyer, tying the first powered flight to the first Moon landing.

What causes the phases of the Moon?

How much of the sunlit half faces Earth changes as the Moon circles us; half of it is always lit, which is why a full Moon, opposite the Sun, always rises around sunset.

What is the average distance from the Earth to the Moon, whose orbit is slightly elliptical?

238,900 miles (384,400 km) is only the average: the oval orbit brings the Moon about 26,000 miles closer at its nearest than at its farthest, which is why some full Moons look slightly bigger and brighter than others.

The Moon's largest dark plain, where Apollo 12 landed, is known as the Ocean of what?

Storms: Oceanus Procellarum, the Ocean of Storms, is the only lunar plain large enough to be called an ocean, and Apollo 12 set down on it within walking distance of a robot probe that had arrived in 1967.

Which numbered NASA mission was the first to land humans on the Moon?

Apollo 11's lunar module touched down on July 20, 1969; Apollo 8 only orbited the Moon and Apollo 10 flew the landing's dress rehearsal without touching down.

What is the term for the Moon's near side always facing Earth?

Tidal locking happened because Earth's gravity raised a bulge in the young Moon and kept tugging on it, braking the Moon's spin until one turn took exactly as long as one orbit.

What name is given to the second full Moon in a single calendar month?

Blue Moon has two rival meanings: the popular one is the second full Moon in a calendar month, but an older rule gives the name to the third of four full Moons in a single season.

Which theory is most widely accepted for how the Moon came to exist?

The giant impact hypothesis says a Mars-sized body struck the young Earth and the debris gathered into the Moon, which would explain why the Moon has so little iron: it was built mostly from rocky outer layers.

The Moon's gravity is approximately what fraction of Earth's gravity?

1/6 of Earth's pull is why moonwalkers seem to bounce in the old footage: Apollo crews tried two-footed kangaroo hops before settling on a loping stride as the easiest way to get about.

Which spacecraft made the first soft landing on the far side of the Moon, in 2019?

Chang'e 4 touched down in Von Kármán crater on 3 January 2019; because the far side never faces Earth, China first parked the Queqiao relay satellite beyond the Moon to carry its signals home.

How many humans walked on the Moon during the Apollo program?

12 men walked on the Moon, two from each of six landings; three further landings, Apollos 18 to 20, were cancelled as budgets shrank, or the tally would have reached eighteen.

What is a lunar eclipse?

The Moon passes through Earth's shadow only at full Moon, and because the shadow darkens the Moon itself, everyone on the night side of the planet can watch, with no eye protection needed.

Which NASA program, begun in 2017, was created to return humans to the Moon?

Artemis, named for Apollo's twin sister in Greek mythology, was established in December 2017; its uncrewed first flight, Artemis I, looped around the Moon in November 2022.

Stepping onto the Moon, Buzz Aldrin summed up the view in which two words?

Buzz Aldrin called the view 'magnificent desolation' moments after stepping off the ladder; he reused the words as the title of his 2009 memoir about the depression that followed his return.

Roughly how wide is the Moon?

About 2,160 miles (3,475 km) makes the Moon a quarter as wide as Earth but much less dense, since its iron core is small: it would take about 81 Moons to match Earth's mass.

Which Apollo astronaut stayed in lunar orbit while his crewmates walked on the Moon during Apollo 11?

Michael Collins circled alone in the command module Columbia, out of radio contact on every pass behind the Moon; he wrote that what he felt there was not loneliness but 'almost exultation'.

Apollo 11's plaque on the Moon says its crew 'came in peace for' whom?

All mankind: the steel plaque, signed by the three astronauts and the US president, is fixed to the ladder of the lander's lower stage, which stayed behind on the Moon as the launch pad for the trip home.

What is a Moon called when it is more than half lit but less than full?

Gibbous comes from the Latin for 'hump', after the bulging shape; a Moon swelling toward full is a waxing gibbous, and one shrinking after it is a waning gibbous.

What is the point in the Moon's orbit where it comes closest to Earth called?

Perigee is why some full Moons look bigger: one that falls there can appear up to 14% wider and 30% brighter than a full Moon at the farthest point of the orbit.

Which lunar plain did Apollo 11's lunar module set down on in July 1969?

Tranquillitatis, the Sea of Tranquility, was picked for being flat and smooth, yet the autopilot was steering for a field of boulders and the commander had to take over and fly on to clear ground.

What is the largest confirmed crater on the Moon?

The South Pole-Aitken Basin, about 2,500 km across and up to 8 km deep, is so big that the blast should have dug up rock from far below the crust, which is why landers are sent there.

Which country was the first to land a spacecraft on the Moon?

The Soviet Union's Luna 9 became the first spacecraft to achieve a soft landing on the Moon on February 3, 1966, three years before the first crewed landing.

Which Roman goddess of the hunt was also worshipped as a goddess of the Moon?

Diana, patroness of hunters and the countryside, was merged over time with the older Moon goddess Luna, so Romans came to honour her as a triple goddess of the hunt, the Moon and the underworld.

Why does the Moon's surface swing from about 250°F by day to far below freezing at night?

It has almost no atmosphere to trap or spread warmth, so ground in full Sun bakes while a patch of shadow a step away is far below freezing.

Who was the last Apollo astronaut to climb off the lunar surface?

Eugene Cernan was last up the ladder on 14 December 1972, after the crew unveiled a plaque declaring that here 'man completed his first explorations of the Moon'.

What causes tides on Earth?

Gravity of the Moon and Sun stretches the oceans into two bulges, one facing the Moon and one opposite; at new and full Moon the two pulls line up and produce the extra-high spring tides.

On the Moon, what is regolith?

Loose dust and rubble blanketing the surface was smashed from bedrock by billions of years of meteorite hits; with no wind or water to round them, the grains stay sharp enough to scratch lenses and wear out seals.

Which gas, making up over 40% of Moon soil by weight but locked into minerals, do engineers hope to extract?

Oxygen is the most abundant element in Moon soil, but it is bound up as oxides in the rock; European engineers have freed it from imitation moondust by electrolysis in molten salt, leaving usable metal behind.

What callsign did the Apollo 11 Lunar Module carry?

Eagle was named for the bald eagle on the mission patch; in the first design the bird held an olive branch in its beak, but a NASA chief thought its bare talons looked too warlike, so the branch was moved to them.

Which Indian spacecraft successfully landed near the Moon's south pole in August 2023?

Chandrayaan-3 set down near the south pole on 23 August 2023, four years after its predecessor's lander lost contact and crashed during the same final descent, and then sent out its small rover, Pragyan.

Measured in Earth time, roughly how long does daylight last at one spot on the Moon?

About 2 weeks of daylight are followed by two weeks of night, because the Moon turns only once for each trip around Earth: sunrise to sunrise takes about 29.5 Earth days.

What name do scientists give the Mars-sized world thought to have been destroyed as the Moon was born?

Theia is named for the Titan who in Greek myth was mother of the Moon goddess; computer models suggest its iron core sank into Earth's own while its rocky debris went into the Moon.

What did Apollo astronauts leave on the Moon for laser measurement of its distance?

Retroreflectors need no power: each simply bounces a laser pulse straight back the way it came, which is why observatories have been able to keep timing the round trip ever since 1969.

Which numbered NASA mission aborted its lunar landing after an oxygen tank explosion?

Apollo 13's oxygen tank ruptured in April 1970 when a routine stir ignited damaged wire insulation; the crew survived by using the lunar module Aquarius as a lifeboat.

What is the term for when the Moon passes directly between the Earth and the Sun?

A solar eclipse can be total only through a lucky coincidence: the Sun is about 400 times wider than the Moon but also about 400 times farther away, so the two look the same size in our sky.

Why can ice survive for billions of years inside some craters at the Moon's poles?

Sunlight never reaches their floors because the Moon's axis is tilted only about 1.5°, so the Sun just skims the polar horizon and these 'cold traps' stay colder than minus 400°F.

Approximately how old is the Moon?

4.5 billion years is nearly Earth's own age, and we know it from radioactive clocks in Apollo rocks: the oldest date to about 4.4 billion years, while rocks from the dark plains are a billion years younger.

What did Apollo 15's astronauts become the first people to do on the Moon in 1971?

Drive a car: David Scott and James Irwin unfolded a battery-powered rover from the side of their lander, which let them explore mountains and a canyon miles from where they touched down.

What is the Moon slowly doing to its orbit around Earth each year?

The Moon is drifting outward about 3.8 cm a year, a recession tracked by lunar laser ranging since 1969; the energy comes from Earth's tides, which are slowly braking our planet's rotation.

In Greek mythology, who was the goddess of the Moon?

Selene drove the Moon's chariot across the night sky, and her name lives on in selenium, an element named for the Moon because it so closely resembled tellurium, which is named for the Earth.

Astronomically, what defines the Harvest Moon?

The Harvest Moon is the full Moon nearest the autumn equinox; for several evenings around it the Moon rises soon after sunset, which once gave farmers extra light to bring in their crops.

The pale highlands of the Moon show that the young Moon was once covered by what?

An ocean of magma once covered the young Moon: as it cooled, light crystals floated to the top and froze into the pale highland rock, anorthosite, while heavier ones sank.

What was NASA's Gateway, shelved in 2026, designed to be?

A small space station in orbit around the Moon was the plan, with hardware promised by Europe, Japan and Canada, until NASA shelved it in March 2026 in favour of building a base on the surface instead.

Why does the Moon turn red during a total lunar eclipse?

Earth's air bends sunlight onto it, letting the red through while scattering the other colours away, so the eclipsed Moon is lit by every sunrise and sunset on Earth at once.

Which astronaut hit golf balls on the Moon?

Alan Shepard, commanding Apollo 14 in February 1971, swung a makeshift six-iron one-handed because of his stiff suit and joked that the second ball went 'miles and miles and miles'.

What percentage of the Moon's surface is visible from Earth over time?

About 59% of the lunar surface is visible from Earth over time; the extra 9% comes from libration, an apparent wobble from the Moon's tilted, slightly elliptical orbit that peeks around both limbs each month.

What is armalcolite, a mineral first found in Apollo 11's Moon rocks, named after?

The mission's three astronauts gave it their surnames: ARMstrong, ALdrin and COLlins. First found in the 1969 samples, the titanium-rich mineral has since turned up on Earth too.

Apollo 12's crew landed within walking distance of which earlier robotic probe?

Surveyor 3 had soft-landed in April 1967; Apollo 12's Conrad and Bean walked over to it on their second moonwalk and cut off parts, including its TV camera, to bring home for study.

What struck Apollo 12's Saturn V twice shortly after its rainy-day launch?

Lightning struck twice in the first minute and scrambled the spacecraft's readings; a young flight controller, John Aaron, recalled an obscure switch setting, 'SCE to Aux', that brought the data back and saved the mission.

Why did Pete Conrad joke about a 'long' step as his first words on the Moon?

To win a bet with a reporter: Oriana Fallaci was sure NASA scripted its astronauts' first words, so Conrad wagered $500 that he could say what he liked, and later said she never paid up.

What did Apollo 15's crew leave on the Moon to honour spacefarers who had died?

A small metal figurine, the Fallen Astronaut, lies beside a plaque naming fourteen American and Soviet spacefarers; the crew placed it in secret and revealed it only after they were home.

What carved Hadley Rille, the winding valley that Apollo 15 landed beside?

Flowing lava formed the channel, and one idea is that it began as a lava tunnel whose roof later caved in; boulders as big as houses now litter its floor.

David Scott dropped a hammer and what else on the Moon to demonstrate Galileo's theory?

Scott let a falcon feather and a geology hammer fall together; with no air to slow either, both struck the surface at the same instant, as Galileo had predicted centuries earlier.

Sent to the Descartes Highlands to collect volcanic rock, what did Apollo 16's crew find instead?

Rubble fused by impacts, known as breccia, filled the sample bags; the surprise overturned the volcanic theory that had picked the landing site in the first place.

Which Apollo moonwalker was the only professional geologist to reach the lunar surface?

Harrison Schmitt got his seat because geologists pressed NASA to fly one of their own before the landings ended; he took the place of Joe Engle, a test pilot who had been in line for it.

Apollo 17's crew landed in which valley, chosen for suspected volcanic features?

Taurus-Littrow, a valley on the southeastern rim of Mare Serenitatis, was picked after orbital photos hinted at volcanism; Cernan and Schmitt landed there on 11 December 1972.

What colour was the soil that thrilled Apollo 17's crew at Shorty crater?

Orange soil turned out to be tiny beads of volcanic glass sprayed out by a fiery eruption over 3.5 billion years ago, not the sign of recent activity that the crew had hoped for.

Orbiting the Moon on Christmas Eve 1968, Apollo 8's crew read from which book?

Genesis, the opening creation verses, was read in turn by all three astronauts on live television; an atheist campaigner sued the government over it, and the courts dismissed the case.

Which astronaut took the famous 'Earthrise' photograph from lunar orbit in 1968?

William Anders shot Earthrise on 24 December 1968 with a modified Hasselblad; stories persisted for years that commander Frank Borman had taken it, but all three frames were Anders's.

What did the Soviet probe Luna 2, the first craft to hit the Moon, carry to scatter as it struck?

Small metal pennants, engraved with 'USSR' and the launch date, were packed into two spheres built to burst apart at the Moon; days later Khrushchev handed President Eisenhower a replica.

Which English radio observatory picked up and decoded Luna 9's first pictures from the Moon's surface?

Jodrell Bank's radio telescope picked up Luna 9's signal in February 1966; staff realised it matched the standard newspaper picture-fax format, and the Daily Express printed the images before the Soviets did.

How much lunar soil did the robotic Luna 16 bring back to Earth in 1970?

101 grams was the whole haul, drilled and sealed up by robot; three specks of it, weighing a fifth of a gram between them, sold at Sotheby's in 2018 for $855,000.

How was Lunokhod 1, the first rover on the Moon, steered across the surface in 1970?

By drivers on Earth: a five-man team steered it from television frames that arrived seconds apart, and kept it going for 321 days, far beyond its planned three months.

Which probe made the first American soft landing on the Moon, in June 1966?

Surveyor 1 touched down on 2 June 1966 and sent back more than 11,000 pictures, along with measurements of how much weight the ground could bear, which NASA needed before trusting a crewed lander to it.

Ranger 7 in 1964 was the first NASA probe to do what?

Send close-up images was all Ranger 7 was built to do before it crashed: after the six Rangers before it had failed, it returned more than 4,300 pictures in its final 17 minutes.

Luna 3's 1959 far-side photos revealed a dark region named after which city?

Moscow gives its name to Mare Moscoviense, the Sea of Moscow, one of only two dark patches in Luna 3's pictures: the hidden side turned out to be rugged, cratered highlands, quite unlike the face we know.

The bright rayed crater Tycho is named after an astronomer from which country?

Denmark's Tycho Brahe, who lost part of his nose in a duel with a cousin and wore a false one, gives his name to a crater only about 108 million years old, young enough for its rays to stay bright.

How did NASA's LCROSS mission test a south-polar crater for ice in 2009?

Crashed a rocket stage into it: the spent Centaur hit the crater Cabeus, and a trailing probe flew through the plume for about four minutes, detecting water, before striking the Moon itself.

In 2020, China's Chang'e 5 made it only the second country to do what on the Moon?

Plant a national flag: Chang'e 5 unfurled a cloth flag made of a composite designed not to fade or warp in the harsh conditions, half a century after the first American one went up.

What nickname did Japan's SLIM lander earn for its precision-landing goal?

Moon Sniper lived up to its name, coming down about 55 m from its target in January 2024, but an engine fault left it resting on its nose with its solar panels turned away from the Sun.

What was Commander Moonikin Campos, which flew around the Moon in NASA's Orion capsule in 2022?

A mannequin wired with sensors sat in the commander's seat to record the vibration and radiation a crew would face; a public vote named it after Arturo Campos, an engineer who helped bring a crippled Apollo crew home.

The word 'supermoon' was coined in 1979 by a member of which profession?

Astrologer Richard Nolle's term has no precise astronomical definition, which is why outlets disagree about how many supermoons occur each year.

India's first lunar probe, Chandrayaan-1, is credited with discovering what in 2009?

Chandrayaan-1's M3 instrument found widespread water and hydroxyl across the lunar surface, announced in September 2009; the orbiter had also dropped a probe that sampled traces of water on its way down to crash near the south pole.

Which country's Beresheet lander crashed on the Moon in April 2019?

Israel's Beresheet, built by SpaceIL and named with the Hebrew for 'in the beginning', crashed on 11 April 2019 after a gyroscope fault led to an engine cut-out; it carried dehydrated tardigrades in a time capsule.

Intuitive Machines' Odysseus, the first private lander on the Moon, ended up how?

Tipped to a 30° angle after it skidded and snapped one of its six legs on touchdown in February 2024, Odysseus kept its instruments working, though the lean slowed its radio link to a trickle.

Which company's Blue Ghost became the first fully successful commercial Moon lander?

Firefly Aerospace's Blue Ghost landed on 2 March 2025 with ten NASA experiments and kept working through the whole lunar day, then for five more hours after sunset until its batteries ran flat.

What did Apollo 14's Stuart Roosa carry around the Moon that was later planted across America?

Tree seeds, hundreds of them, rode in the kit of Roosa, a former forest firefighter; the bags burst open during decontamination and the seeds were feared dead, yet nearly all sprouted into 'Moon trees'.

Which company built the Lunar Roving Vehicle that Apollo astronauts drove on the Moon?

Boeing developed the 210-kg rover in just 17 months; it rode to the Moon folded up against the side of the lander, and the astronauts lowered and unfolded it with a system of ropes and pulleys.

Which aerospace company built the Apollo Lunar Module?

Grumman, of Bethpage, New York, built the two-stage lander; after one served as a lifeboat for a crippled Apollo crew in 1970, the firm sent the command module's maker a joke invoice for towing.

NASA's Lunar Prospector carried the ashes of which scientist to the Moon in 1998?

Eugene Shoemaker, co-discoverer of comet Shoemaker–Levy 9, died in 1997; Lunar Prospector carried a capsule of his ashes and was steered into a south-polar crater, later named Shoemaker, in July 1999.

Japan's lunar orbiter Kaguya is named after a princess in which folktale?

The Tale of the Bamboo Cutter tells of Kaguya-hime, found as a baby inside a glowing stalk of bamboo, who at the story's end reveals where she came from and goes home to the Moon.

Apollo 10's lunar module, flown to within miles of the surface, had which call sign?

Snoopy swooped to within about 15 km of the surface in May 1969 while the command module Charlie Brown waited; its upper stage was then fired off into orbit around the Sun, the only Apollo lander sent there.

The first meteorite recognised as coming from the Moon was found in 1982 where?

Allan Hills 81005 was picked up in Antarctica in January 1982; a Smithsonian scientist saw that it matched the highland rocks Apollo crews had brought home, proving that pieces of the Moon can fall to Earth.

Which lunar sea on the western limb famously resembles a bullseye target?

Mare Orientale means 'Eastern Sea', though it sits on the Moon's western edge: it was named in 1906, when maps put east on that side, and its rings, about 930 km across, are hard to make out from Earth.

What did Buzz Aldrin do in 2002 when a Moon-hoax believer called him a liar to his face?

Punched him: Bart Sibrel had cornered Aldrin outside a Beverly Hills hotel, demanding he swear on a Bible that the landings were real, and prosecutors declined to bring charges.

Which 2024 mission was the first to return samples from the far side of the Moon?

Chang'e 6 landed in a far-side crater named Apollo in June 2024 and brought home about 1.9 kg; with no line of sight to Earth, it had to work through a relay satellite launched ahead of it.

Roughly how far did the Soviet rover Lunokhod 2 drive across the Moon in four months of 1973?

About 40 km in four months set a record for driving on another world that stood until 2014, when NASA's Opportunity finally passed it after ten years on Mars.

Why is 'dark side' a misleading name for the Moon's far side?

It gets just as much sunlight as the side we see; 'dark' only ever meant unseen, since no one had laid eyes on it until a Soviet probe photographed it in 1959.

Which 1967 pact bars any nation from claiming sovereignty over the Moon?

The Outer Space Treaty opened for signature in three capitals at once on 27 January 1967; its Article II bars national appropriation, so planting a flag confers no ownership.

The 1902 film 'A Trip to the Moon' was written, directed and produced by which filmmaker?

Georges Méliès, a Paris stage magician turned filmmaker, built the film on Jules Verne's novels; American firms, Edison's among them, copied and sold it without paying him, so he opened a New York office to fight the pirates.

Johannes Hevelius, who published the first atlas of the Moon in 1647, made his living in which trade?

Brewing beer paid for it all: Hevelius, from a family of wealthy Danzig brewers, built an observatory across the roofs of his three houses and spent four years charting the Moon himself.

What happened to the cotton seedlings that sprouted aboard a Chinese Moon lander in 2019?

They froze when night fell: the sealed canister, which also held potato seeds, yeast and fruit-fly eggs, could not be kept warm, and the experiment ended after nine days as it sank to minus 52°C.

Why don't eclipses happen at every new and full Moon?

The Moon's orbit is tilted about 5° to Earth's path around the Sun, so in most months the Moon passes just above or below the line-up and the three bodies never quite align.

Why do some astronomers call Earth and the Moon a 'double planet'?

The Moon is so large beside its planet, over a quarter of Earth's width, that no other planet's moon comes close; by the usual test the pair still falls short, because the point they both circle lies inside Earth.

Why is Thomas Harriot little known for drawing the Moon by telescope months before Galileo?

He never published them: Harriot sketched the Moon in July 1609, months ahead of Galileo, but his drawings stayed in private papers until 1784 while Galileo's 1610 book took the fame.

What name is given to the faint glow sometimes seen on the dark part of a crescent Moon?

Earthshine is sunlight that bounces off Earth, lights the Moon's night side and comes back to our eyes; Leonardo da Vinci sketched it and guessed the cause five centuries ago.

Apollo astronauts said the Moon dust clinging to their spacesuits smelled like which substance?

Spent gunpowder is the smell and taste reported for lunar dust. Its fine particles are also sharp and very clingy.

The Moon is smaller than the planet Mercury but considerably larger than which of these worlds?

Pluto, the largest dwarf planet, is considerably smaller than the Moon. The Moon itself ranks as the fifth largest natural satellite in the Solar System.

Which animals flew around the Moon aboard the 1968 probe Zond 5, months before any astronaut did?

Tortoises were chosen because they were easy to strap in securely. The pair lost about a tenth of their body weight on the trip but showed no loss of appetite.

The Moon's surface reflects about as much light as which material?

Worn asphalt is the usual comparison, because the Moon bounces back only about 12% of the light that hits it. Even so, it outshines everything else in the night sky.

Why does the Moon look so much bigger near the horizon than when it is high in the sky?

An optical illusion is to blame: a pebble held at arm's length covers the Moon just as well high or low. The low Moon is in fact about 1.5% farther away.

In the English nursery rhyme 'Hey Diddle Diddle', which animal jumped over the Moon?

Cow is the answer, and the rhyme is sometimes simply called 'The Cow Jumped over the Moon'. Its modern form was first printed in London around 1765.

With almost no air above it, what colour is the daytime sky seen from the Moon's surface?

Black is the colour of the lunar sky even at midday, because the Moon's atmosphere is negligibly thin. The same is true on airless Mercury.

Compared with the view from Europe, how does the Moon appear to skywatchers in Australia?

Upside down is how it looks, because the Southern Hemisphere sees the Moon rotated 180°. The lit edge even appears to grow from the opposite side as the weeks go by.

Which day of the week takes its English name from an Old English phrase meaning 'Moon's day'?

Monday comes from the Old English 'monandaeg'. Japanese and Korean share the idea: their word for the same day also means 'day of the moon'.

In the animated film 'A Grand Day Out', Wallace and Gromit rocket to the Moon to find which food?

Cheese is what the pair go looking for after finding their fridge empty on a bank holiday. In the film's world, the Moon really is made of it.

Which US president told a Houston crowd in 1962, 'We choose to go to the Moon'?

John F. Kennedy gave the speech to about 40,000 people at Rice University's stadium. A 1961 poll had found 58 percent of Americans opposed to his Moon goal.

Which animal do Chinese and Japanese folk tales see in the Moon, pounding with a mortar and pestle?

Rabbit is the shape picked out; in Japan and Korea it is pounding rice cakes rather than a magic elixir. China named its 2013 lunar rover Yutu, 'Jade Rabbit', after an online poll.

The Moon rises from which part of the horizon?

East is where the Moon comes up, just as the Sun and stars do, because our planet spins eastward. The exact spot swings north and south of due east over each month.

Which planet is the brightest object in Earth's night sky after the Moon?

Venus ranks third among the brightest objects in Earth's sky, behind only the Sun and the Moon. It shines so strongly that it is commonly misreported as a UFO.

Which Renaissance artist explained earthshine, the faint glow on the dark part of a crescent Moon?

Leonardo da Vinci worked out that the glow is light bounced off our own planet, though he credited the oceans rather than the clouds. It is sometimes called the Da Vinci glow.

Which French author fired three travellers from a giant cannon in 'From the Earth to the Moon'?

Jules Verne published the novel in 1865 and did rough sums for his space gun, some of them remarkably accurate. He even sited the launch in Florida.

A bright ring around the Moon on a hazy night is moonlight bent by what, high in the atmosphere?

Ice crystals, millions of them and each six-sided, bend the light into a ring about 22 degrees from the Moon. Folklore says such a ring warns of a coming storm.

Which widely used calendar is purely lunar, so its 354- or 355-day year drifts through the seasons?

Islamic dates follow the Moon alone, with nothing added to pull them back into line with the Sun. The whole cycle slips right round the seasons in about 33 years.

Long cliffs are forming on the Moon because, as its interior cools, the whole globe is doing what?

Shrinking is the cause: the Moon has contracted by about 90 metres in the past billion years. Its brittle crust wrinkles much as a grape does on the way to becoming a raisin.

What name do scientists give the Moon's atmosphere, so thin that it is very nearly a vacuum?

Exosphere is all the Moon has for an atmosphere, and the whole thing weighs less than 10 tonnes. Its traces include neon blown in on the solar wind.

Which term describes the slow rocking of the Moon that lets observers peek slightly around its edges?

Libration comes partly from the Moon's uneven pace: it speeds up and slows down along its path while turning at a steady rate, so it seems to nod from side to side.

What do astronomers call the moment the Moon passes in front of a star or planet and hides it?

Occultation of a star is abrupt: with almost no lunar air to dim it, the star winks out at the Moon's edge in a tenth of a second or less.

Which term describes the Sun, Earth and Moon lying in a straight line, as at every new and full Moon?

Syzygy covers any three celestial bodies in a row. When a distant light, a massive object and an observer line up the same way, the result is an Einstein ring.

Which volcanic moon of Jupiter is the only natural satellite denser than Earth's Moon?

Io edges out the Moon by about 5 percent in density because it is rock almost through and through, with less water than any other known body in the Solar System.

Which ibis-headed Egyptian god of writing and wisdom was also a god of the Moon?

Thoth may owe his ibis head to the bird's curved beak, which Egyptians possibly saw as a crescent moon. Millions of the birds were mummified and buried in his honour.

The 1835 'Great Moon Hoax' claimed which real astronomer had seen bat-winged people on the Moon?

John Herschel was initially amused by the six newspaper articles, noting that his real observations could never be as exciting. Reporter Richard Adams Locke later admitted writing them.

The Moon and our planet both circle a shared balance point, the barycentre, which lies where?

Inside the Earth is right: the balance point sits about 4,671 km from the planet's centre, roughly three-quarters of the way out to the surface.

Which term names the farthest point of the Moon's orbit, about 405,500 km from Earth?

Apogee puts the Moon about 11.6% farther away than its closest approach. The long axis joining the two extremes swings right round once every 8.85 years.

Soon after it formed, the Moon is thought to have been covered by a deep global ocean of what?

Molten rock hundreds of kilometres deep is the theory, proposed in 1970 from rock fragments in the first Apollo samples. Light crystals floated to the top to form the crust.

Which rare isotope, lodged in lunar soil by the solar wind, is often proposed as a future fusion fuel?

Helium-3 has built up in the Moon's top layer over billions of years. Fusing it would release no dangerous neutron radiation, though one critic calls mining it on the Moon magical thinking.

Which English band's 1973 album 'The Dark Side of the Moon' begins and ends with a heartbeat?

Pink Floyd meant the title as a nod to lunacy rather than astronomy. The record went on to sell more than 45 million copies.

Whose 1964 recording of 'Fly Me to the Moon' became closely linked with NASA's Apollo missions?

Frank Sinatra's version was played on a portable cassette player aboard Apollo 10 as it circled the Moon. The song began life in 1954 under the title 'In Other Words'.

Which composer's Piano Sonata No. 14, finished in 1801, is known as the 'Moonlight Sonata'?

Ludwig van Beethoven never used the nickname. It grew from a poet's later image of a moonlit lake; the composer's own label was 'Sonata quasi una fantasia'.

Which Christian festival falls on the first Sunday after the first full Moon on or after 21 March?

Easter moves from year to year because it follows the Moon, and working out its date is a calculation known as computus. The full Moon used is a calculated one, not the one in the sky.

Which unit of the calendar has an English name that grew from the same root as the word 'Moon'?

Month and Moon are cognates, because a month began as the time the Moon takes to run through its phases. Twelve such cycles fall about 11 days short of a full year.

The ocean tides raised by the Moon act as a brake that is gradually slowing what?

Earth's rotation is slowing, so the day grows by about 17 microseconds every year. Timekeepers add the occasional leap second to keep clocks in step.

The Moon's small core, only about a fifth of its radius, is thought to be mostly which metal?

Iron, alloyed with a little sulfur and nickel, is the likeliest recipe for the Moon's core. A solid inner ball is thought to be wrapped in a shell of liquid metal.

Buzz Aldrin reported that Apollo 11's flag did what as the lunar module's engine fired for takeoff?

Blew over is what he saw, because the flag stood only about 27 feet from the lander. Later crews took care to plant theirs farther away.

Travelling at the speed of light, how long does moonlight take to cross the gap to Earth?

About 1 second, or 1.3 to be exact, is all it takes to cross a gap roughly 30 times the width of our planet. Sunlight, by comparison, needs about eight minutes to arrive.

Which actress first sang 'Moon River', on a fire escape in the 1961 film 'Breakfast at Tiffany's'?

Audrey Hepburn accompanied herself on the guitar for the scene. Henry Mancini and Johnny Mercer wrote the song for her to sing, and it won the Academy Award for Best Original Song.

The Moon's steady pull is credited with keeping which feature of our planet from swinging wildly?

Axial tilt is what the Moon steadies. Without that pull, one analysis suggests the planet's lean could swing as far as 90 degrees within a few million years.

Around the Moon's first and third quarters, coasts get their weakest tides, known by which name?

Neap tides have the smallest gap between high and low water, and come about seven days after the strongest ones. Those 'spring' tides are not named after the season.

Which insects were the first animals shown to navigate by polarisation patterns in moonlight?

Dung beetles of one African species were found to steer this way. Their relatives are the only insects known to orient themselves by the Milky Way.

Which comic-book hero reached the Moon with Captain Haddock in a story collected in 1954?

Tintin made the trip in 'Explorers on the Moon', praised as uncannily accurate. Hergé had a model rocket with detachable parts built so that his team could sketch from it.

Seeing a human face in the Moon's dark patches is a classic example of which trick of perception?

Pareidolia is the tendency to find a meaningful image where there is none. Another well-known case is the Face on Mars, a rock formation that looked human in certain satellite photos.

Which American author wrote 'The Moon Is a Harsh Mistress', about a lunar penal colony's revolt?

Robert Heinlein won the 1967 Hugo Award for the novel. It popularised the motto TANSTAAFL: 'There ain't no such thing as a free lunch'.

Which ancient Greek, later charged with impiety, taught that the Moon shines by reflected sunlight?

Anaxagoras also held that the Moon was earthy and had mountains, and that the Sun was a mass of red-hot metal. He ended up in exile in Lampsacus.

Which 19-year cycle, credited to an Athenian astronomer, returns Moon phases to the same dates?

Metonic cycles of 235 lunar months overshoot 19 years by only about two hours. The Babylonian calendar used the pattern to decide which years needed a thirteenth month.

In Norse mythology, which brother of the Sun, Sól, is the Moon personified and is chased by a wolf?

Máni and his sister cross the sky every day to count the years for mankind, each with a wolf in pursuit. His name is simply the Old Norse word for 'Moon'.

The Moon's whole surface, about 38 million square kilometres, is comparable in area to which region?

The Americas match the whole Moon for area, so each lunar hemisphere is roughly one continent's worth: North America on one side, South America on the other.