50 Fun Facts About Time Travel

Which author's 1895 novella popularised the idea of travelling through the years by mechanical means?

H. G. Wells. His title gave English the phrase 'time machine', and he had already tried the idea out in a college-magazine story, 'The Chronic Argonauts'.

In the 1895 novel The Time Machine, the gentle Eloi are preyed on by which underground race?

Morlocks. The Time Traveller decides they descend from workers once banished underground, who by the year 802,701 are farming the idle rich for meat.

In Prisoner of Azkaban, Harry and Hermione use a Time-Turner to save Sirius Black and which creature?

Buckbeak. The hippogriff has been sentenced to death, so the pair lead him away just before the execution, and Sirius Black then escapes on his back.

In Star Trek IV: The Voyage Home, the crew journey to 1986 San Francisco to collect which animals?

Humpback whales. An alien probe is wrecking 23rd-century Earth while calling to the long-extinct species, so Kirk's crew fetch a pair to answer it.

In Washington Irving's 1819 tale, Rip Van Winkle sleeps through which war?

The American Revolution. He dozes off a loyal subject of King George III and wakes 20 years later to find the inn sign repainted as General Washington.

In Mark Twain's A Connecticut Yankee in King Arthur's Court, how is Hank Morgan sent back to Camelot?

A severe blow to the head. A workmate fells Hank with a crowbar; in Camelot he escapes the stake by 'commanding' a solar eclipse he remembers from history.

In Slaughterhouse-Five, Billy Pilgrim is abducted by aliens from which planet?

Tralfamadore. Its aliens see every moment of time at once, which is why they greet each death with a shrug: 'So it goes.'

In Back to the Future, what speed must the DeLorean reach to travel through time?

88 miles per hour. Marty first hits it by accident, flooring the DeLorean to escape the Libyan gunmen who have just shot Doc.

In Back to the Future, how much power does the DeLorean need to travel through time?

1.21 gigawatts. In 1955 the only thing that can supply that much power is a bolt of lightning, so Doc wires the car to the town's clock tower.

In early drafts of Back to the Future, the time machine was built into which household appliance?

A refrigerator. The film-makers dropped it for fear that children would copy Marty, climb into a fridge and get trapped, so the DeLorean got the job.

Which actor was originally cast as Marty McFly and replaced by Michael J. Fox after filming began?

Eric Stoltz. He filmed for weeks before the makers decided he was playing a comedy far too seriously and reshot his scenes with Michael J. Fox.

In Back to the Future, what happened on November 5, 1955, the destination date Doc enters?

He conceived his invention. Doc slipped while hanging a clock in his bathroom, knocked himself out and came round with a vision of the flux capacitor.

What does TARDIS stand for in Doctor Who?

Time And Relative Dimension In Space. In the first episode the Doctor's granddaughter Susan claims she made the name up herself, yet other Time Lords use it too.

The Doctor's TARDIS is stuck in the shape of what obsolete British object?

A police box. Its chameleon circuit is meant to disguise the ship wherever it lands, but the circuit jammed in 1960s London and no repair has lasted.

Doctor Who's first episode aired the day after which event?

JFK's assassination. The news so overshadowed the launch that the BBC showed the first episode again a week later, just before the second.

In The Terminator, which machine intelligence sends a cyborg back to 1984?

Skynet. By 2029 it is losing its war with the human resistance, so it sends a Terminator to kill the leader's mother, Sarah Connor, before he is born.

James Cameron got the idea for The Terminator from what?

A fever dream. Sick in Rome, Cameron had a nightmare of a metal skeleton dragging itself out of a fire, and built the whole film around that image.

Terry Gilliam's 12 Monkeys is based on which French short film?

La Jetée. Chris Marker told it almost entirely in still photographs; its only moving footage is a few seconds of a woman waking and opening her eyes.

In 12 Monkeys, James Cole is sent back from 2035 to trace the source of what?

Deadly virus. Cole is not sent to stop the outbreak, only to gather information on the original strain so that the future can develop a cure.

In Bill & Ted's Excellent Adventure, what shape is the time machine?

A phone booth. The script first used a 1969 Chevrolet van, dropped for being too much like the DeLorean in Back to the Future.

In Groundhog Day, Phil Connors relives which date over and over?

February 2. Phil escapes Punxsutawney's endless Groundhog Day only after he stops exploiting the loop and spends the day helping the townspeople.

In Hot Tub Time Machine, what do the friends spill on the tub's controls?

Energy drink. The spill sends them back to 1986, and they have to get the can of illegal Russian 'Chernobly' back from a ski-patrol bully before the tub can take them home.

In Somewhere in Time, Christopher Reeve's character travels to 1912 by what method?

Self-hypnosis. The spell holds until he finds a penny dated 1979 in his pocket, which drags him back to the present and leaves him unable to return.

In Outlander, time-travelling nurse Claire Randall tries to head off which battle, Bonnie Prince Charlie's final defeat?

Culloden. Claire knows from her own century how the Jacobite rising ends, so she and Jamie go to Paris to choke off its funding, and fail.

Which author's 1979 novel Kindred sends a Black writer back to a slave plantation?

Octavia Butler. Her heroine Dana is dragged from 1976 Los Angeles to Maryland whenever her slave-owning ancestor Rufus is in danger, and must keep him alive so that she will one day be born.

In The Time Traveler's Wife, Henry DeTamble's involuntary time travel is caused by what?

A genetic disorder. Henry can take nothing with him when he vanishes, so he arrives naked every time and has taught himself to pick locks and steal clothes.

Shane Carruth's cult time-travel film Primer was made for roughly how much?

$7,000. Carruth, a former engineer, wrote, directed, edited, scored and starred in it himself, and the result still won Sundance's Grand Jury Prize.

In Avengers: Endgame, the heroes reach the past through what?

The Quantum Realm. Scott Lang emerges from it having lived five hours while five years passed outside, which gives the Avengers the idea for their 'time heist'.

Which action star plays a time-travelling federal agent in the 1994 film Timecop?

Jean-Claude Van Damme. His agent Max Walker uncovers a senator who is sending men into the past to get rich, all to bankroll a run for president.

In physics, what are spacetime paths that would let an object return to its own past called?

Closed timelike curves. General relativity allows them on paper, which is why physicists have gone looking for a deeper law that rules them out; none has been proved.

Which logician's 1949 rotating-universe solution to Einstein's equations would allow travel to the past?

Kurt Gödel. The result upset his friend Einstein, who had hoped his theory ruled such trips out; the catch is that Gödel's universe does not expand, and the real one does.

Which paradox asks what happens if a time traveller goes back and prevents their own birth?

The grandfather paradox. Back to the Future plays it out with parents instead: once Marty keeps his mother and father apart, he and his siblings start fading from a family photo.

Under Novikov's self-consistency principle, any attempt to change the past will what?

Always fail. In the physicists' test case, a billiard ball sent back to knock its younger self off course only ever lands a glancing blow that sends it on its way.

Stephen Hawking's suggestion that the laws of nature forbid time travel is called what?

The chronology protection conjecture. Hawking argued that the energy of virtual particles would soar just as a time machine formed, and joked that this keeps the past 'safe for historians'.

Wormholes are also known as bridges named after which two physicists?

Einstein and Rosen. Their 1935 bridges turned out to be useless as shortcuts: later work showed one would collapse too quickly for even light to get through.

Which physicist, who also popularised the term 'black hole', gave spacetime shortcuts the name 'wormholes'?

John Archibald Wheeler. In a 1957 paper he and Charles Misner borrowed the word for an insect's tunnel through fruit, suggesting physicists 'might perhaps be excused' for so vivid a term.

In relativity's twin thought experiment, how does the twin who flew off at near light speed come home?

Younger than the other. It looks like a paradox because each twin sees the other's clock run slow, but only the traveller turns round, so the two journeys are not symmetrical.

After 803 days in orbit, cosmonaut Sergei Krikalev's clock is out of step with Earth's by about how much?

0.02 seconds. Orbital speed and weaker gravity tug a clock in opposite directions, and even the winner shifts it by only millionths of a second a day.

Which real-world technology has to correct for relativistic time dilation to work?

GPS satellite navigation. Its orbiting clocks gain about 38 microseconds a day on clocks on the ground; left uncorrected, position fixes would drift by roughly 10 km every day.

The Hafele-Keating experiment tested time dilation by doing what?

Flying atomic clocks around the Earth. In 1971 the pair took four caesium clocks twice round the world on ordinary scheduled airliners, and found them out of step with ground clocks, as relativity predicted.

In Time Bandits, six dwarfs hop through history using a map stolen from whom?

The Supreme Being. He had hired the dwarfs to patch the holes left in his creation; they kept his map of those holes and use it to rob the rich of every era.

In Interstellar, each hour the crew spends on Miller's water planet costs how long back on Earth?

Seven years. The planet orbits so close to the black hole Gargantua that time there crawls, and one bungled landing ends up costing the crew 23 years.

In the Talmud, Honi sees a carob tree planted, sleeps 70 years, then finds whom picking its fruit?

The planter's grandson. In the Babylonian Talmud's telling, the man had said he was planting for his descendants, since a carob takes 70 years to fruit; back home, nobody believes Honi is who he says.

Which Japanese legend has a fisherman return from a short stay away to find generations gone?

Urashima Tarō. In the familiar telling he is carried to an undersea palace for rescuing a turtle, and when he opens the box he was told to keep shut, all his missing years catch up with him at once.

At the end of 1968's Planet of the Apes, which ruined landmark tells Taylor he was on Earth all along?

The Statue of Liberty. Taylor's crew woke from hibernation believing they had reached another world, but they had landed in the far future of their own, now ruled by apes.

In Ray Bradbury's 'A Sound of Thunder', a time-travelling hunter changes the future by crushing what?

A butterfly. Eckels panics on a dinosaur hunt and steps off the path; back home the spelling on signs has changed and a would-be dictator has won the election.

Which hypothetical particle would always travel faster than light, and so could carry signals into the past?

Tachyon. Gerald Feinberg coined the name in 1967 from the Greek for 'swift', and Gregory Benford's novel Timescape has scientists use tachyons to warn the past of a coming disaster.

Stephen Hawking threw a party for time travellers in 2009 and sent out the invitations when?

After it was over. Only a visitor from the future could have known to turn up, and when nobody did, Hawking called it experimental evidence that time travel is not possible.

In Looper, Joseph Gordon-Levitt plays a hitman who must kill his older self, played by whom?

Bruce Willis. Gordon-Levitt wore facial prosthetics to pass for a young Willis; a looper's final job is to 'close the loop' by shooting the man he will become.

In the 2014 film X-Men: Days of Future Past, whose consciousness is sent back to 1973?

Wolverine. Only his healing power can survive so long a trip; in the original 1981 comic it was Kitty Pryde who went back, and in the film she is the one who sends him.