It's likely that you've seen video of ferrofluids doing things like growing spines when exposed to magnets, or being built up into sculptures by artists using magnetic fields. But what if they're not just artistic triumphs? What if ferrofluids can act as models and let scientists learn about the multiverse?
Researchers at The University of Maryland and Towson University have suggested studying ferrofluids as a way of understanding how multiverses form. This first sprang from an interest in metamaterials as ways to model physical behavior. Metamaterials are human-made materials that exhibit characteristics which no one sees in natural materials. They happen to coincide, in some behaviors, with the odder bits of the physical universe. In fact, the researchers argue applying a strong magnetic field to the vacuum of space itself makes it act like a metamaterial.
They specifically took a look at ferrofluids, which are fluids with metal filaments suspended in them. When a magnetic field is applied to them, they create elaborate solid structures. They're not metamaterials in and of themselves, but under certain influences, they form tiny columns and groups of wires that function as metamaterials. Specifically, they form hyperbolic metamaterials. Hyperbolic metamaterials play tricks on light; light moving one way will interact with the material like it's a metal, while light traveling another way will act with the material as if it were transparent glass. The researchers keep the ferrofluids at a point just before they turn into a hyperbolic metamaterial, and let random thermal fluctuations in the ferrofluid kick it up so it develops pockets of hyperbolic metamaterial briefly and spontaneously.
That's interesting enough, but the scientists believe that studying the material and its fluctuations can teach us about little multiverses that appear and disappear in the greater universe. The way that light moves through this material is analogous to how people picture Minkowski spacetime. This is a four dimensional spacetime, with three physical dimensions and one extra dimension that signifies time. Unfortunately, human beings can't see time as a physical dimension. (Note: If you can do this, please do contact us for an interview.) The pockets of hyperbolic metamaterial in the ferrofluid could seen as Minkowski spacetime in two dimensions, with the third dimension signifying time. This, humans can see, and while it's not a perfect copy of regular Minkowski spacetime, it is a good model. So the thermal fluctuations in these ferrofluids could be giving us a picture of how multiverses pop up in the four dimensional spacetime of our universe.
Top Image: Gregory F Maxwell