Earth’s inhabitants are in danger of being swallowed up by the sun. So the United Earth Government comes up with a plan to thrust the Earth out of orbit and send the planet beyond our solar system to its new home as a satellite of Proxima Centauri.
Such is the out-of-this-world premise for The Wandering Earth. In February, the Mandarin-language sci-fi action movie rapidly became the second-highest grossing film in Chinese box office history. Its worldwide box office total now stands at just shy of $700 million. Netflix quickly snatched up streaming rights to The Wandering Earth for over 190 countries, including the United States.
After the film’s impressive theatrical run, Netflix added the movie to its streaming library on May 5 with zero fanfare. (It wasn’t even included in Netflix’s May newsletter sent to press.)
The hit movie is based on the 2000 short story of the same title by Liu Cixin, best known for his Hugo Award-winning novel, The Three-Body Problem.
The Wandering Earth’s premise may sound ridiculous, but it turns out much of the film’s science holds up better than you might expect.
Here’s the official premise from Netflix:
The Wandering Earth tells the story of a distant future in which the sun is about to expand into a red giant and devour the Earth, prompting mankind to make an audacious attempt to save planet. The multi-generational heroes build ten-thousand stellar engines in an effort to propel Planet Earth out [of] the solar system, in the hope of finding a new celestial home. During the 2,500 year-long journey, a group of daring heroes emerge to defend human civilization from unexpected dangers and new enemies, and to ensure the survival of humanity in this age of the wandering Earth.
“Things that I would have expected it to gloss over, I was happy to see that they actually addressed. So it looked like they did their homework to an extent,” says John Elliott, a senior engineer at NASA’s Jet Propulsion Laboratory in Pasadena, California.
Indeed, The Wandering Earth filmmakers did their homework. Four scientists from the Chinese Academy of Scientists consulted on the film.
Inverse spoke with Elliott, a systems engineer and vision architect at JPL, to play “what if?” and determine what aspects of The Wandering Earth are feasible and what parts are a stretch.
This article contains some spoilers for The Wandering Earth.
A Helium Flash in the Near Future
Let’s start there. In The Wandering Earth, scientists have determined that a helium flash from the sun is nigh. Do we need to worry about the sun unleashing a burst of blazing hot helium on us anytime soon? Short answer: probably definitely not.
Helium flashes are known to occur in stars in the red giant phase. Our sun won’t become a red giant for another 5 billion years.
Elliott’s an engineer though, so “never” and “no way” aren’t exactly in his vocabulary.
“I would not be one to say there couldn’t be something that goes wrong in the sun that causes this to happen, but it’s not in current theory,” he says.
Thrusting Earth Out of Orbit
Now, let’s imagine that a helium flash is a verified danger, and we do need to relocate the Earth. If that still sounds absurd to you, hang tight while we break it down with Elliott’s help.
In The Wandering Earth, the journey from Earth’s orbit to Jupiter’s neighborhood takes 17 years. Elliott kindly took the time to run some numbers for us: To move that distance in 17 years would take roughly 10 kilometers per second of delta-v.
(Elliott notes, though, that it depends on how you do the math to know what that exact number would be — it could be anywhere between 8 and 16 kilometers per second.)
There are 10,000 “Earth engines” in the film propelling the planet through space. To provide 10 kilometers per second of delta-v to the mass of the Earth (rounded to 6 x 1024 kilograms) over 17 years, each of those engines would need to produce a continuous 2.5 x 1015 pounds of thrust, Elliott says.
That’s a number wildly beyond realistic capabilities once you consider the real-world F-1 engine, Elliott notes. The F-1 engine used on Saturn V (a launcher which NASA used from 1967 to 1973) is the most powerful single-nozzle, liquid-fueled rocket engine ever developed, according to NASA’s website. Alas, this legendary engine falls short of what the engines of The Wandering Earth would need: a single F-1 engine that puts out 1.5 million pounds of thrust.
“Pretty inconceivable” is how Elliott sums up the movie’s giant engines.
In Liu’s short story (translated into English by Holger Nahm), the largest Earth engines are 6,000 feet taller than Mount Everest.
“Well, I don’t know how you would build something that big,” Elliott says.
But even if you could build engines large enough, mining the Earth (as these engines do in the film) causes a problem. There would barely be any Earth left by the point you mined enough dirt to thrust the planet to Proxima Centauri, 4.2 light-years away.
“It would take about 95 percent of the mass of Earth to do this,” Elliott estimates.
Other Ways to Keep Safe From a Helium Flash
So if thrusting the Earth through the galaxy is out, what would be a more realistic way to save the human race?
The best plan may be to “get as many people as you can off the Earth,” Elliott says.
He notes that “you’re not likely to go anywhere outside the solar system with current technology or even projected technology.”
Settling on nearby planets might be the way to go. Perhaps Mars would become habitable if the sun expands. “Would it warm it up enough that the water that’s sub-surface now would melt and cause an atmosphere?” Elliott wonders. Ganymede, an icy moon of Jupiter, might also become a decent contender for a new home.
Stopping Earth’s Rotation (?!?)
Let’s accept that the Earth could be thrust toward the next-closest star. We’ll now examine how the rest of the film holds up.
To use these giant engines, first the Earth’s rotation is stopped. The resulting widespread tsunamis (and limited space in underground havens) seem to be to blame for Earth’s population being reduced to 3.5 billion.
Though Elliott says he finds it “a little odd” that the United Earth Government was willing to accept that level of casualties, he says the tsunamis themselves are a realistic consequence of halting the Earth’s rotation.
“If you’re going to stop the Earth rotating, the oceans are gonna splash over everything when you slow down,” Elliott says. “It does depend on how fast they stopped [the rotation], but it would be hard to conceive of them stopping it very quickly just because of the mass. I don’t know if there’s a [speed at which] you could stop it when you wouldn’t get extreme flooding.”
Elliott continues: “You’d have flooding, you’d have earthquakes, tectonic plates would be screwed up and moving around.”
Conditions on the Surface of the Earth
Several years after Earth has stopped rotating and is on its way to Alpha Centauri, siblings Qi and Duoduo journey out of the safety of underground early, and a display screen in the elevator indicates that the temperature on the surface near Beijing is -84° Celsius (a brisk -119.2° Fahrenheit). Thermal suits protect them from the icy conditions outside.
Elliott says -84° Celsius on the bright side of the Earth while it’s in Jupiter’s neighborhood “didn’t seem non-credible to me,” while the dark side of the Earth “might be well below that.”
By comparison, daytime temperatures on Ganymede, Jupiter’s largest moon, range from -297° to -171° Fahrenheit.
The JPL engineer notes that Earth has its own internal heat — both that and the planet’s atmosphere means Earth would take some time to cool down. It seems that the sun hasn’t reached red giant status yet by this point in the film, so an expanding sun would not keep the Earth warm as it reaches the outer edges of the solar system.
What About the Moon?
In all of the film’s shots of the wandering Earth, the moon is nowhere in sight.
Leave the moon behind? “You can’t just do that,” Elliott says.
The engineer explains that if the speed of the Earth moving through the solar system is accelerating, “the moon’s gonna adjust its orbit as you move, and as it does that, it’s gonna get into an unstable orbit,” Elliott notes. “And depending on how fast they’re accelerating and how fast they’re moving away, I would not be surprised if [the moon] ran into [Earth].”
As for how (somehow) getting rid of the moon would affect the Earth’s tides, well, remember, stopping the Earth’s rotation has already messed with the oceans and tectonic plates.
“You’ve already done so much to the surface of the Earth by stopping the rotation that I think the tidal forces aren’t gonna be a big issue by that time,” Elliott points out.
A Gorgeous Jet Stream
The moving Earth is depicted on screen with a jet stream trailing behind it. The image seems almost too picturesque to be plausible.
“It was maybe a little artistically enhanced, but given the size of everything in this, you probably would see something like that,” Elliott says.
He further explains: “The way they show the engines, I guess they don’t tell you a lot, but the implication is they’re basically using dirt and propelling that out of these engines. And with that much propulsion and that much thrust and that much force, you probably would see a dust trail.”
As for real-life images of something similarly picturesque, Elliott suggests checking out images of Saturn’s outermost ring (E-ring) and its sixth-largest moon, Enceladus. The E-ring is largely composed of icy water vapor that has burst out of geysers on Enceladus.
Jupiter’s Great Red Spot
Also supplying stunning visuals in The Wandering Earth is our solar system’s largest planet. Jupiter looming over Earth’s sky is quite a sight. The Great Red Spot is on full display above Sulawesi in the film’s climactic moments.
If you’ve heard that the Great Red Spot is shrinking, you may be quick to deem this a goof.
It’s not explicitly stated in The Wandering Earth when the film’s events take place, but a frost-covered stadium boasting a 2044 Olympic Games label in Shanghai tells us that the film takes place sometime after 2061 since the planet’s been on the move with everyone tucked underground for 17 years.
So will Jupiter’s iconic massive storm (twice as wide as the Earth!) still be brewing 42 years from now? About a year ago, Business Insider reported that the Great Red Spot may disappear within one or two decades. According to a post on NASA’s website by Elizabeth Zubritsky, “Researchers don’t know whether the spot will shrink a bit more and then stabilize, or break apart completely.”
The film’s apparent proposition that the Great Red Spot will hold out for at least another four decades “didn’t really bother me,” Elliott says. “There’s a chance that it will go away, but, being a weather-related thing, it’s always hard to predict.”
The plan is to slingshot Earth around the solar system’s largest planet. This concept is basically a Jupiter gravitational assist, which Elliott says is “a reasonable thing for them to do.”
Real scientists used a Jupiter gravitational assist on the Cassini mission, which sent a probe to study Saturn.
How humans would fare that close to Jupiter, though, is another matter. Jupiter’s intense radiation field would be a problem, for one.
Much of The Wandering Earth film adaptation focuses on Earth nearing Jupiter — an approach that gets too close. Our planet goes off-course and is at risk of colliding into Jupiter rather than slingshotting around it.
“If you were doing a mission like this, you’d do all these trajectory correction maneuvers, and you would always know exactly where you were and make sure you were on course,” Elliott says. “You wouldn’t wait until a week before you were too close to figure that out.”
But this is a suspenseful action movie, so of course we get too close to Jupiter. At that point, humans across the globe are warned that Jupiter is “capturing Earth’s atmosphere” and people will die of asphyxiation.
This dramatic turn does seem to be a plausible expression of the Roche limit, which is the minimum distance at which a satellite can approach another celestial body without being broken apart by tidal forces.
“When you get to the Roche limit, yes, stuff would start being sucked off,” Elliott explains.
Final Thoughts: The Appeal of The Wandering Earth
Elliott says he can see why The Wandering Earth would find box office success.
“The science in it is compelling. It’s realistic enough that it’s not just something that you’d dismiss,” he says. “It’s got the one big thing about moving the Earth, which is hard to accept, but once you accept that, the rest of it kind of flows from that.”
The Wandering Earth is an epic action flick that channels movies like Armageddon and Roland Emmerich’s collection of disaster movies. The director, Gwo Frant, has cited Terminator 2: Judgment Day as an influence.
The fast-paced, high-octane vibe of these movies is a stark contrast to the cadence of the short story that inspired The Wandering Earth’s screenplay. Like Liu’s Remembrance of Earth’s Past (the trilogy that begins with The Three-Body Problem), the short story Wandering Earth spans several generations.
Title cards in the film do lay out the 2,500-year plan — 500 years accelerating, 1,300 years coasting, and then 700 years decelerating before firing up rotation again by Proxima Centauri — but the movie primarily takes place within a suspenseful 36-hour period.
The movie focuses on characters solving the immediate problem of a potential collision with Jupiter. It’s an effects-laden film that depicts human resilience in the face of a majorly daunting (but quickly solved) challenge.
The Wandering Earth was released in China on the first day of the Lunar New Year, and the filmmakers amped up the emotion of that human resilience with values the holiday is meant to celebrate. Hope and the idea of a family reunion fuel the characters’ determination to save Earth — much like July 4 provides the rousing backdrop to Independence Day.
The idea of Earth being in danger of getting burned up by the sun naturally calls to mind the real-world dangers of global warming. Has that very real threat ever been made into a big-budget movie? Yes, sort of.
The highest-profile film about global warming is yet another installment in the lineup of high-octane disaster movies: Emmerich’s The Day After Tomorrow, the 2004 film that depicts climate change at a rapid pace.
But, hey, if the movie followed the short story or the pace of real-life science more closely, we wouldn’t have been treated to this memorable disaster movie line: “Let’s light up Jupiter!”
The Wandering Earth is currently available to view on Netflix in several territories, including the United States. It is scheduled to debut on Netflix in Australia and New Zealand on August 5, 2019.