Spoiler-free guide to the science of Interstellar
This is going to require some serious science.
The film's hard-science pedigree is guaranteed by its science advisor and executive producer, Kip Thorne, one of the world's leading experts on Einstein's theory of general relativity. "The things he was able to open up for me were far more exotic and exciting than anything I could've come up with as a screenwriter," Nolan told New Scientist.
Some critics have said they wished they'd brushed up on their physics before seeing the film – so here's our spoiler-free guide to everything you need to know before you see Interstellar.
What is this "dust" that threatens the Earth's food supply?
The agent of destruction is a blight fungus. In the film, set on an Earth of the near future, the blight is sweeping across the world, and has already destroyed wheat and okra as a crop. In the real world, blight is indeed a serious threat – responsible for the Irish potato famine – and a different blight fungus, Ug99, now threatens wheat. Norman Borlaug, dubbed the father of the Green Revolution, said Ug99 "has immense potential for social and human destruction".
Nolan was influenced by the real-life ecological disaster of the Dust Bowl in 1930s North America, when the rich top soil essential to farming dried out and blew away, desolating vast areas and causing famine and mass human displacement – a situation that could yet happen again with the severe, ongoing US drought in the US.
But chin up people. Consider the movie's tagline: the end of Earth will not be the end of us.
How can we ensure the survival of the human race?
Colonising our neighbouring planets and their moons will be the first step. Once we've arrived at our new home we need to grow crops and establish a viable population.
Poor old Anne Hathaway, playing Interstellar's only female astronaut, Amelia Brand, isn't expected to do all this herself – she is taking a whole load of frozen human embryos with her. Presumably some artificial wombs, too.
But as Stephen Hawking has argued, the long-term survival of our species depends on us developing interstellar travel.
Even if we don't render our planet uninhabitable, the sun will eventually swell up and engulf Earth. This won't happen for 5 billion years, but nevertheless, Michael Caine's character in the film – based on Thorne – insists we have to travel through a wormhole to another galaxy. "We must confront the reality that nothing in our solar system can help us," he says.
How could we travel to planets beyond our solar system?
It's a long way to the nearest exoplanets. To get there without spending thousands of years on the journey, the options are limited. Physics won't let us go faster than the speed of light, but it will allow for radical shortcuts. There are efforts to devise Star Trek-inspired warp drives, but even if they were possible, they could be deadly. That leaves the main contender: wormholes.
Wormholes are hypothetical tunnels through space-time – predicted by Einstein's general theory of relativity – that can connect distant parts of the universe.
Until recently, wormholes have been seen as unworkable curiosities. That's now changed. Physicists have described how you could make a one big enough to send a message or a spaceship Movie Camera through – or even reunite star-crossed loversMovie Camera.
We can even visualise what it would look like to travel through one – rendered here with slightly cheaper graphics software than in Interstellar.
We won't manage to make a wormhole for a while – that will take a highly advanced civilisation. If we do ever get to go through one, who knows what we'll find when we get out. The crew on the Interstellar spaceship, the Endurance, discover an unwelcome beast at the other side of theirs: a supermassive black hole.
What are the real dangers of approaching a black hole?
The beautiful black hole in Interstellar is not just visually stunning, it is scientifically accurate. At the heart of a black hole is a singularity, a point of effectively infinite density. This exerts a lot of gravity, which drags matter towards it, spiralling into the hole in a vast swirl called an accretion disc.
Kip Thorne worked out the mathematics of what happens to the accretion disc, and found that the intense gravity warps the disc around the black hole, creating the spectacular halo that is one of the movie's visual highlights. It's a phenomenal achievement.
If you fall into a black holeMovie Camera, or get too close to its intense gravity (and somehow survive), you'll notice weird things happening to time. This is a favourite Nolan trope, also used in his mind-bending hit Inception, in which time moved at different speeds depending on the dream state his characters were in.
Gravity's time-warping effect intensifies the heart-wrenching separation between Matthew McConaughey's character, Cooper, and his 10-year-old daughter, left back on Earth. Astronaut twins Mark and Scott Kelly's ages diverged by roughly 10 milliseconds when one of the brothers was on the International Space Station, but Cooper can't know how old his daughter will be if he ever gets back to Earth.
McConaughey said being away from his own daughter brought this feeling home. "It happens all the time, whether you're dropping your kids off at school or going on a vacation. This is the most extreme nature of that. This is a father going off for a long time. There's no guaranteed return ticket."