Silke Weinfurtner is trying to build the universe from scratch. In a physics lab at the University of Nottingham—close to the Sherwood forest of legendary English outlaw Robin Hood—she and her colleagues will work with a huge superconducting coil magnet, 1 meter across. Inside, there’s a small pool of liquid, whose gentle ripples stand to mimic the matter fluctuations that gave rise to the structures we observe in the cosmos.
Weinfurtner isn’t an evil genius hell-bent on creating a world of her own to rule. She just wants to understand the origins of the one we already have.
The Big Bang is by far the most popular model of our universe’s beginnings, but even its fans disagree about how it happened. The theory depends on the existence of a hypothetical quantum field that stretched the universe ultra-rapidly and uniformly in all directions, expanding it by a huge factor in a fraction of a second: a process dubbed inflation. But that inflation or the field responsible for it—the inflaton—is impossible to prove directly. Which is why Weinfurtner wants to mimic it in a lab.
If the Big Bang theory is right, the baby universe would have been created with tiny ripples—so-called ‘quantum fluctuations’—which got stretched during inflation and turned into matter and radiation, or light. These fluctuations are thought to have eventually magnified to cosmic size, seeding galaxies, stars, and planets. And it’s these tiny ripples that Weinfurtner wants to model with that massive superconducting magnet. Inside, she’ll put a circular tank, some 6 centimeters in diameter, filled with layered water and butanol (the liquids have different densities, so they don’t mix).
Then, her group of researchers will kick in the artificial gravity distortions. “The strength of the magnetic field varies with its position,” says Richard Hill, one of the paper’s co-authors. “By moving the pool to different regions of the field, the effective gravitational force can be increased or decreased,” he says, “and can even be turned upside-down.”
By varying gravity, the team hopes to create ripples—but unlike those on a pond, the distortions will appear between the two liquids. “By carefully adjusting the speed of the ripples we can model an inflating universe,” says another team member, Anastasios Avgoustidis. In cosmic inflation, space rapidly expands while the ripples of matter propagate at a constant speed—and in the experiment, the speed of the ripples rapidly decreases as the liquid’s volume remains constant. “The equations describing the propagation of ripples in these two scenarios are identical,” Avgoustidis says.
Not everyone is convinced that simulating our universe’s first moments in the lab will help cosmology, though. Ted Jacobson of the University of Maryland thinks that such experiments are “not so much verifying something we are uncertain about, but rather implementing and observing it in a lab.” Why mimic the universe in the lab? “It’s fun. And it may suggest new phenomena we didn’t think of in cosmology,” he says.
Avi Loeb, an astrophysicist at Harvard University, is not as optimistic.
The real test of inflation would be, Loeb says, the production of the substance that propelled it—the inflaton—in the lab. But this would require reaching energies up to a trillion times larger than those achieved in our most powerful particle accelerator, the Large Hadron Collider—and such a test seems unlikely in the near future.
“Just mimicking the equations of an analogous system is a metaphor to the real system, not an actual test of its fundamental properties,” says Loeb. It’s like “smelling food instead of eating the actual food,” he adds, only “the latter has the real value.”
That’s true, but sometimes the smells from a kitchen can tell you a lot about what was served for dinner.
