Fermi's controversial experiment, conducted to search for possible signs that our universe may be a hologram, found nothing. It is called Holometer ("holographic interferometer"), and it is the brainchild of Fermi laboratory physicist Craig Hogan. He came up with it in 2009 as a way to test the so-called holographic principle.
Back in the 1970s, physicist Yaakov Bekenstein showed that information about the interiors of a black hole is encoded on its two-dimensional surface ("boundary"), and not in its three-dimensional volume. Twenty years later, Leonard Susskind and Gerard t'Hooft extended this idea to the entire universe, likening it to a hologram: our three-dimensional universe in all its beauty flows from a two-dimensional "source code". New York Times journalist Dennis Overbye likened the hologram idea to a soup can. All the "substance" of the universe, including humans, constitutes the "soup" inside the jar, but all the information describing this substance is written on the label on the border of the jar.
Initially, Susskind treated the idea as a metaphor, but after doing some calculations, he came to the conclusion that it could be completely literal: the three-dimensional universe can be a projection of two-dimensional information on the border.
Since then, the holographic principle has become one of the most influential ideas in theoretical physics, although many consider it untestable, at least for now. (Verification would require close-up probing of the black hole, a daunting prospect for which we don't have any technology yet.) Hogan decided to try it anyway. Holometer looks for a special type of holographic noise - a kind of quantum shudder of space-time - using a rather modest setup: an array of lasers and mirrors in a dank underground tunnel, with a control room located in a trailer. However, no one said that physics should be glamorous.
Holometer uses a pair of laser interferometers positioned next to each other, each sending a 1-kilowatt beam of light through a beam splitter and down two perpendicular arms, 40 meters each. The light is then reflected back into the beam splitter, where the two beams are connected. (Somewhat similar to the mechanics of eLISE, which will look for gravitational waves).
If there is no movement, the newly collected rays will be the same as the original beam. But if fluctuations in brightness are observed, scientists will then analyze those fluctuations and see if the space vibrations have affected the separator.
Locating such a detail is of course very difficult because there are many other things that can be mistaken for a jitter, including wind and traffic noise. When preliminary results came out in April, they weren't the most promising. So it may come as no surprise that the final analysis was completely fruitless.
The $ 2.5 million experiment was controversial from the start, and among the skeptics were the inventors of the holographic principle themselves. So theoretical physics is openly gloating. As noted by Sabin Hossenfelder, a physicist at the Nordic Institute for Theoretical Physics and one of the critics of the experiment, “The Holometer results are ready: nothing. No wonder, as the underlying idea is meaningless."
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Hogan remains optimistic. In the end, zero result is also a result, and a theoretical model needs to be worked out to exclude all possibilities. “This is just the beginning of the story,” he says. “We have developed a new way of exploring space and time that we didn’t have before. We don't even know if we have reached the right sensitivity."