The first moments after the birth of the universe are shrouded in mystery. Partly because we cannot see far enough into the past. However, scientists believe that the universe underwent a huge expansion immediately after the Big Bang, but it is not at all clear how this rapid inflationary stage unfolded.
Now a team of physicists has created a kind of tiny, expanding universe using a “quantum field simulator” made of supercold atoms, the study published in the journal Nature, reports. The experiment was able to simulate different versions of warped space-time that fit models of the universe as either spherical or hyperbolic in geometry. These adjustable distortions of space-time affect how particles are formed, among many other factors.
The purpose of the experiment was to explore the dynamics that might be similar to the early universe under various scenarios in the laboratory, with the ability to suspend the entire system and analyze it in more detail—something that cannot be done with the real universe.
The success of the experiment suggests that such simulators “offer the possibility of entering unexplored regimes” in quantum physics, which studies matter and energy at the tiny scale of atoms, the study said. Although no experiment can produce conditions directly comparable to those of the early universe, the new experiment probes mechanisms that may be analogous to the physics governing spacetime and particle production in the moments after the Big Bang.
“We’re definitely not the first experiment to do some kind of expansion or to show this particle production,” said Nikolas Liebster, an experimental physicist at Heidelberg University in Germany who co-authored the study, in a call with Motherboard. “But we’re the first to put it in this specific context of how these different kinds of inflationary histories—like an accelerated universe, a decelerated universe, or a constantly expanding universe—can change the particles that you produce.”
Liebster and his colleagues explored these questions by cooling about 20,000 potassium-39 atoms down to temperatures barely above absolute zero (roughly around -400°F). In this frigid environment, the atoms form what’s known as a Bose–Einstein condensate, which is a state of matter that can be used to simulate the kinds of exotic physical phenomena that occur around black holes or in the early universe.
The condensate in this experiment was a superfluid, that is, a liquid that has no viscosity, and had the shape of a two-dimensional pancake. The setup could be configured to simulate different theories of cosmic inflation, as well as different types of space-time warping, such as flat, spherical, and hyperbolic models.
By passing sound waves through the condensate — an analogue of the light that permeates the universe — Liebster and his colleague were able to probe the strange physics of each model, which might be similar to what arose in the early universe. The sound waves in the experiment played the role of light waves in the real universe, as their path through the condensate was affected by different configurations.
“It could be that in the past, our universe had different kinds of spatial curvature, and that’s what we can tune in our system,” Liebster explained. “We have control over those kinds of parameters.”
The team was able to simulate stoppable patterns of cosmic inflation to study the dynamics behind them, which Liebster called a “a dream in cosmology.”