Separating the Science From the Fiction in Sunshine
When director Danny Boyle and producer Andrew Macdonald (28 Days Later, Trainspotting) enlisted the help of leading experimental physicist Brian Cox as the scientific advisor on their new film Sunshine, one might have finally expected a movie that makes up for so many years of far-fetched Hollywood science fiction.
Not quite. While Sunshine boasts Dr. Cox's esteemed track record (a research fellow at the Royal Academy, the United Kingdom's national academy of science, and a member of the team working at the world's largest particle accelerator), dazzling simulated images of the Sun, and a plot borrowed from cutting-edge particle physics, it's ultimately about as plausible as Bill and Ted's Excellent Adventure.
Set 50 years in the future, Sunshine imagines that the Sun is dying prematurely. The Earth is blanketed by ice and a crew of astronauts has set out to deliver a nuclear payload into the Sun's center to recharge it.
While the story might recall the asteroid-detonating plot of Michael Bay’s Armageddon (1998), the mission aboard Icarus 2 is far more complex: Here, the astronauts aim to destroy a supersymmetric particle called a Q-Ball that is eating the Sun from the inside out.
First posited some 20 years ago by Harvard physicist Sidney Coleman, a Q-Ball is a super-heavy object that could have formed during the Big Bang and would have the ability to break down ordinary matter made of protons and neutrons. Normally, protons are stable because they are the lightest particles to carry a conserved quantum number called the baryon number, and there is no way for them to get rid of this number and decay. But Q-balls, made from tightly packed supersymmetric particles that can accommodate a baryon number at lesser energetic cost than a proton, allow the proton to disintegrate, while the baryon number of the Q-ball increases. Q-Balls, says Dr. Cox, "can be pictured as giant agglomerations of supersymmetric particles that could, if they drifted into the heart of a star, eat away like a cancer, eventually destroying the star from within."
In the film, it is up to astrophysicist Robert Capa (played by Cillian Murphy) to stop this process by launching a "stellar bomb" into the sun's core. Consisting of uranium and dark matter, the mysterious quantity of unobservable matter in the universe that exerts a gravitational force, the detonation would recreate the super-heated conditions in which the Q-Ball was made, splitting it up into benign supersymmetric particles called squarks. Then the sun could shine again.
But there are several major problems on which this premise rests, not least of which is that supersymmetry and Q-Balls are as yet completely unproven. Even Cox admits that our sun is not dense enough to hold a hypothetical Q-Ball. Because the supersymmetric Q-ball is a very compact assembly of heavy particles packed in a small volume, it is billions of times denser than an atomic nucleus, so it would fly right through the sun "like a knife through whip cream," says UCLA physicist Alexander Kusenko, one of the leading Q-Ball researchers. Kusenko theorizes that a more likely target for a Q-Ball is a neutron star, which is far denser than the sun.
But for argument's sake, even if a Q-Ball did invade the sun and started eating the solar matter, New York University's Georgi Dvali, co-author with Kusenko and Mikhail Shaposhnikov of the paper "New Physics in a Nutshell, or Q-ball as a Power Plant," says the energy released by this process would be so high that "the intensity of the sun's radiation should increase enormously." He adds, "So then the problem of our civilization will not be the sun's death, but rather enormous radiation before it."
As Kusenko says, "You would not be freezing, you would be fried."
UCLA professor of solar physics Roger Ulrich doubts that humankind would even be around if the Earth got to a point where it was freezing over. By that point, as he sees it, the sun would have already passed through the red giant phase into a cooling white dwarf. "Well before the sun makes it too cold for us, we are going to get seriously roasted and quite possibly the whole earth could be evaporated and incorporated into the solar gas," he says.
Then there's the problematic issue of the film's conception of a "stellar bomb," which in Dr. Cox's configuration, works like an atomic bomb. Instead of normal explosives setting off the uranium into a nuclear explosion, the stellar bomb uses uranium to create a dark matter explosion.
But separating Q-balls into squarks with a nuclear explosion is "like trying to disintegrate a ship in the ocean with wind," says Kusenko. "The wind may have a lot of power, but the energy density is small, so the ship is not going to disintegrate."
Plus, Kusenko explains, the fundamental properties of dark matter—that it does not directly engage with normal matter—would make it impossible to be hauled in a spaceship. He offers another analogy: "If you try to push fog with your hand, it'll just push right through your hand."
The film also presents the more straightforward quandary of whether a spaceship could actually get close enough to a weakening, but still powerful sun in the first place. While it may sound unfeasible, Dr. Joseph B. Gurman, a U.S. Project Scientist for the Solar and Heliospheric Observatory, says there are currently plans for a Solar Probe that could come as close as 3 or 4 solar radii—2.1 million to 2.8 million km—from the visible surface. "Basically, they'd use a ceramic heatshield," he explains, not unlike those depicted in the film. "At that perihelion, closest approach distance, you wouldn't want to fold away your heat shield ever." Then again, shooting a missile from such a distance would make for a far less dramatic climax than what is depicted in the movie.
So is there a better way of rebooting our dying sun, when it does expire in an estimated five billion years? Kushenko is at a loss. "I don't have any good ideas," he says. "Nuclear bombs don't seem like a feasible option."
Still, Ulrich says that it might be possible to "fully mix" the sun by dropping a properly sized black hole into its center. "After accreting enough matter, it would settle to the center and produce energy in such a way that the outer layers would mix," he says.
But there's one final catch: Even if futuristic humans did discover a way to remix the sun's energy, it would take thousands of years for those rays to reach the Earth—and by then, no one would be around to get a tan.
Dr. Cox is aware of the film's scientific shortcomings. But he contends that shouldn't detract from the ability of Sunshine to raise vital questions about the universe's confounding and dangerous nature. "What is certainly true is that our position on the fragile Earth is far from secure," he says. "We live in a violent universe that we certainly do not fully understand."
Anthony Kaufman has written about films and the film industry for The New York Times, The Los Angeles Times, The Wall Street Journal, Slate, Seed, Variety, The Village Voice, and indieWIRE.