Scientists are creating a mini universe and simulating black holes

We're creating simulators for phenomena in the universe that we have no direct access to in the lab. So what we have here is really a black hole in a box and in the new experiment we've moved to a universe in a box. In the glass cryostat on my right we generate a rotating vortex with super fluid helium and that acts as a simulator for the space-time around a rotating black hole. We use surface waves on top of a rotating super fluid as the analog of light waves that are trapped in the vicinity of a rotating black hole and then using a set of high-speed cameras we can observe those waves on the surface and we can see what kind of dynamics that they have in that inaccessible region. The big missing question at the moment in physics in general is the relationship between quantum mechanics and gravity. So what we are trying to do in this experiment is create something that mimics space-time which is the domain of relativity and gravity theory with a material that has very quantum properties. It gives us a way to start approaching the question from an experimental perspective as to whether or not gravity is a quantum field like all the others or if it genuinely stands apart the way that mathematics as we currently understand it makes it seem. Once this experiment really ran its course we wanted to upgrade and start looking at different types of space-time geometries. Now we've moved to a universe in a box. We're trying to create a flat two plus one dimensional space-time and then we're looking at excitations which are the equivalent of particle excitations in a quantum field in that flat space-time. We have a closed experimental cell which we fill with helium gas and then we cool the whole system down so the helium transitions into a superfluid and it forms a very thin film that coats the inside of the cell. Now the fridge has got all of these pumps running to keep everything cold and that introduces some mechanical vibrations. Those drive tiny surface waves on top of that thin film. The film is the analogue of our flat two dimensions of space one dimension of time and those excitations on the surface those are like the excitations of a single quantum field and what we're really interested in is do all observers agree on what those excitations look like. So the idea is we take a pair of beams from a single laser source we split that beam one goes through the cryostat through that thin film of helium and back out at the front where it's then recombined with the beam that we originally split off and by interfering these two expanded beams and using the interference at different points in space we can actually develop a hologram of what those surface fluctuations look like and the equivalent here in the analog system is if we can measure the kind of density of all of these different waves of different wavelengths in the system that's akin to counting the particles of different energies in our toy universe and we're going to introduce a second laser probe. This beam is going to be in a constant circular motion so it's probing these excitations at different points around a circular path and the question is when we compare our stationary observer to our rotating accelerating observer do they agree on the number of particles that they can count in this toy universe? So Unruh predicted that the accelerating observer should see particles that a stationary observer wouldn't and this gives us a way to look for those particles directly in an analog system rather than looking for this really infinitesimally tiny effect out in the real universe. This is a philosophical problem more than anything. On one level you can say well it makes sense that we could have different observers seeing different numbers of particles because we're used to particles being created and destroyed all the time but the number of particles in the universe should be some really fundamental number that arguably everybody should agree on and if two observers disagree about the contents of the universe then you've got to start asking yourself which one is real? What does real even mean when you start asking how many particles are in the universe? So this is a really fundamental question about are the things that we take for granted that we observe in nature objective or is you know reality something that's just locally defined by the observer that's looking and this is potentially going to be one of the first experiments that can actually shine a light on that sort of thing.