Physicists at Fermilab in Illinois have turned on a laser-based experiment that could reveal whether the three-dimensional world we perceive is merely a "Matrix"-style illusion generated by a cosmic two-dimensional hologram.
The Holometer experiment is the result of years of work by particle astrophysicist Craig Hogan and his colleagues at the federally funded Fermi National Accelerator Laboratory, and it could provide the first clear evidence for the existence of the holographic universe. The concept has been debated for decades, but it's devilishly difficult to show whether it can ever be anything more than a concept.
Hogan aims to find out whether the universe is a hologram by looking for telltale quantum jitters in the fabric of space-time itself. "If we see something, it will completely change ideas about space we've used for thousands of years," he said in a news release.
Reidar Hahn / Fermilab
A photo taken with a wide-angle lens from above shows the heart of the Holometer as a Fermilab researcher works on the apparatus.
The Holometer — short for "holographic interferometer" — consists of two interferometers, each of which fires a 1-kilowatt laser beam at a beam splitter, and then down two perpendicular 130-foot (40-meter) arms. The laser light is then reflected back to the beam splitter and recombines. If the splitter has moved slightly due to jitters in the space-time continuum, subtle fluctuations in the light should reveal the effect.
The apparatus is moving all the time, of course — but the Holometer is tuned to detect differences on the scale of less than a millionth of a second. Scientists should be able to filter out the effects of physical motion as well as radio noise from the electronics in the lab.
"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."
How space-time (might) work
The traditional view is that our universe has three spatial dimensions, with time serving as the fourth dimension. String theorists say the equations that govern quantum mechanics and gravity become more elegant if the universe has six or seven additional dimensions. Physicists will be looking for evidence of those higher dimensions when Europe's Large Hadron Collider starts up again next year.
The physicists behind the holographic principle go in a different direction: They take their cue from the theoretical study of black holes — that is, the suggestion that all of the information that's locked up inside a black hole could be encoded on the 2-D surface of its event horizon.
Theoretically, the entire universe could be structured in the same way: Like a hologram, a cosmic 2-D surface could encode all of the information for a 3-D space. The concept could provide a basis for tying together quantum mechanics and gravity — one of the biggest challenges in theoretical physics.
"Determining how space-time is constructed is a pretty big deal for a physicist," Hogan told NBC News in an email. "A holographic model aims to improve on the conventional view of how space-time relates to matter, which has been problematic and paradoxical since quantum mechanics was invented."
The model makes it sounds as if we're in "The Matrix" movie series — where the characters experience a colorful, vibrant world that's generated by a drab underlying reality. But if that's the case, how could we ever tell?
Hunting for the hologram
That's where the quantum jitters enter the picture: If the universe is a hologram, the space-time continuum should be made up of separate 2-D bits, comparable to the pixels on a TV or computer screen.
Look closely enough at your screen, and the seemingly smooth picture breaks down into individual, noisy bits. In a similar way, the Holometer is designed to look closely for noisy bits at what's known as the Planck scale, where the size of each "pixel" is roughly 10 septillion (10^25) times smaller than an atom. Theory suggests that at that scale, the pixels of space-time should jitter in accordance with quantum uncertainty.
"We have the tool ready now — the best ever developed for high-frequency variations of space-time," Hogan said. "The instrument has the raw sensitivity for a highly significant detection."
The Holometer includes two interferometers in evacuated 6-inch steel tubes about 130 feet long. Optical systems (not shown here) in each interferometer "recycle" laser light to create a steady, intense laser wave with about a kilowatt of laser power to maximize the precision of the measurement. The outputs of the two photodiodes are correlated to measure the holographic jitter of the space-time the two machines share.
Hogan has long been intrigued by the possibility of detecting holographic noise. Several years ago, his interest grew when he heard that the GEO600 experiment in Germany had picked up some anomalous laser-light readings. "They've never published about that, since to them it's essentially just an unaccounted nuisance for their gravitational-wave detection," he told NBC News.
Now that the Holometer is in operation, Hogan, Chou and other members of the Fermilab team can begin gathering data — and looking for the subtle signature of holographic noise. That could take years.
"Most of the time from here on will be spent not just sitting back and waiting for the data to roll in," Hogan said, "but in active investigations of all the possible sources of noise."
First published August 27 2014, 12:31 PM