A controversial experiment has indicated that the universe is not a hologram. Researchers from the Fermi National Accelerator Laboratory (Fermilab) have taken it upon themselves to test one of the cornerstones of string theory and quantum gravity.
The holographic principle affirms that all the matter and energy in the universe can be explained in terms of information on a “screen”. If this was true, theories would need one less dimension to explain everything, e.g. a 3D universe could be described in term of its 2D properties.
The Fermilab Holometer tested if it was possible to precisely know a 3D position to a very small scale (10-35 meters, 10 million billion times smaller than a quark). If the universe was a hologram, thus requiring one less dimension than the ones we see, we might not be able to measure all direction – forward-backwards, up-down, left-right – with the same precision. The team called this uncertainty “holographic noise.”
To test this, the scientists used an interferometer, a system of lasers and mirrors that can spot subtle differences in the light during its journey from emission to the detector. Craig Hogan, the theoretical physicist behind the experiment, believes that if the universe was a hologram then lasers sent in different directions will not find the position precisely. The holographic noise will make the laser “jiggle” and the instruments are able to detect these minimal changes. No jiggle was detected.
A scientist working on the Beam Splitter Station of Fermilab Holometer. Credit: Fermilab
The experiment is controversial because a lot of physicists don’t believe that the holographic principle would require the existence of a noise. Yanbei Chen, a theorist at the California Institute of Technology in Pasadena, stated in an article in Science that he doesn’t fully understand the theory behind the holographic noise, but he commends Craig Hogan and the Fermilab team for looking into an experimental confirmation of string theory predictions.
"At least he's making some effort to make an experimental test," Chen said in a statement. "I think we should do more of this, and if the string theorists complain that this is not testing what they're doing, well, they can come up with their own tests."
The results were presented at a talk at the Fermilab near Chicago, Illinois and they are available on ArXiv.
