Do we live in a 2D hologram? There's no short answer, but physicists believe it may be possible. The holographic principle -- a property of particle physics' string theory -- proposes that information about a region of space can be ascertained by the information on the surface that surrounds it -- much like you can determine, say, currents in water by the eddies on the surface.
But does this actually mean that our universe is an optical illusion created by light diffraction? Fermilab has just switched on a machine that may help a team of researchers figure it out: the Holometer, the most sensitive instrument ever built to measure the quantum jitter of space.
They liken the idea to a television, where pixels become less cohesive the closer you get to the screen. Those tiny pieces of data, however, holistically form a recognisable image when you move away from the screen; the researchers believe the universe may be contained in the same way, with the "pixel" size of space roughly 10 trillion times smaller than an atom -- the smallest distance possible in the universe, called the Planck length.
The Holometer uses a pair of inteferometers -- devices used to superimpose waves to compare them -- placed close together to each send a one-kilowatt laser (equivalent to 200,000 laser pointers) at a beam splitter and down two 40-metre arms arranged in a perpendicular L-shape. The light is reflected back to the beam splitter, and, if there is motion, this will cause fluctuations in brightness. It is these fluctuations that the researchers will analyse, looking for holographic noise.
This is expected to occur in all frequencies, but the researchers will be looking for noise that can't be explained away, such as radio waves emitted from nearby electronics. Because the frequency the Holometer is working at is extremely high -- millions of cycles per second -- the motions of normal matter are not likely to affect results, which makes matters a little less complicated.
"If we find a noise we can't get rid of, we might be detecting something fundamental about nature -- a noise that is intrinsic to space-time," said Fermilab physicist Aaron Chou, lead scientist and project manager for the Holometer. "It's an exciting moment for physics. A positive result will open a whole new avenue of questioning about how space works."
This will allow the machine to gauge the limits of the universe's ability to store information. If there are a finite number of bits that tell you how to locate something, for instance, there will come a point at which no more information is available.
"We want to find out whether space-time is a quantum system just like matter is," said Fermilab Center for Particle Astrophysics director Craig Hogan. "If we see something, it will completely change ideas about space we've used for thousands of years."
The Holometer experiment is expected to continue to gather data over the coming year.