A scientist’s courageous experiment, now under construction in Illinois, will attempt to test these ideas by the end of next year using what will be two of the world’s most precise clocks.

Skeptics of the test abound, but their caution comes with good reason: The smallest pieces of space, time, mass and other properties of the universe, called Planck units, are so tiny that verifying them by experiment may be impossible. The Planck unit of length, for example, is 10 trillion trillion times smaller than the width of a proton.

Craig Hogan, a particle astrophysicist at Fermilab in Illinois, isn’t letting the seemingly insurmountable barrier stop him from trying.

Hogan is following through on a radical idea to confirm Planck units with two of the most precise clocks in the world (now under construction at Fermilab). Deemed holometers, each L-shaped laser interferometer will have two perpendicular, 131-foot-long arms to scan for pixelation in the very fabric of space and time.

“What we’re looking for is when the lasers lose step with each other. We’re trying to detect the smallest unit in the universe,” Hogan said. “This is really great fun, a sort of old-fashioned physics experiment where you don’t know what the result will be.”

The two holometers, now being built in a roof-covered ditch of sorts on Fermilab’s sweeping high-energy physics campus, will initially be stacked almost on top of one another to listen for the same Planck-scale “noise.” Once the machine is calibrated and environmental interference is accounted for, Hogan says it should only take a matter of minutes to see if the devices simultaneously see it.

Should they detect something significant, Hogan’s team will then separate the machines and run the experiment all over again. If the noise they measure next isn’t correlated between the machines, it could be the calling card of space-time’s resolution.

Inspiration for the holometer came from such a noise picked up by an experiment called GEO 600. Designed to detect gravity waves — ripples in space-time caused by things like colliding black holes, the machine is a laser interferometer like the holometer will be, yet has arms 15 times longer and a lower-frequency laser source (to be sensitive to gravity waves, if they exist).

Experimental physicist Hartmut Grote, of the Max Planck Institute in Germany, said he and his colleagues at GEO 600 have been unable to pinpoint the source.

“In the past, [Hogan] became a little bit driven, even excited for some time, that this noise could be a result of the holographic principle,” Grote said.

The holographic principle, derived from weirdness theorized to occur at the boundaries of black holes, says reality could be a 3-D projection of a 2-D surface of information. It’s much the same way a hologram printed on a credit card creates the illusion of a 3-D object but, as Hogan explained, we can’t perceive the 2-D surface.

“We could be living inside that 3-D projection, with the truer vision of it as a 2-D sheet hidden by scale,” Hogan said.

Ultra-precise devices such as laser interferometers might be able to detect noisy fluctuations in the projection, which Grote says might “blow up” the pixelation to a larger, detectable size. Yet Grote suggests Hogan’s holometers, which are slated to be finished in a year, may be too late if progress with GEO 600 continues on-schedule.

“We are not at the point where we can verify the noise we discovered is holographic, but we can falsify it as soon as our instrument is more sensitive than the limits of Hogan’s theory,” Grote said. “I’m confident we will reach that point over the next half of a year and find the source of the noise.”

Hogan maintains his cheeriness for the endeavor, even if much of the physics community remains skeptical. But Grote says Hogan has good reason to be upbeat.

“I think it’s a reasonable design to measure this effect, even though I think it’s unlikely he’s going to measure something,” Grote said. “If anything happens, he’ll put to rest another exotic theory about the universe.”

If he does find a limit to the universe’s resolution by exploiting the cosmos’ possible holographic underpinnings, however, Grote said it will make waves.

“It would be a very strong impact to one of the most open questions in fundamental physics,” he said. “It would be the first proof that space-time, the fabric of the universe, is quantized.”

Via: symmetry breaking

Images: Fermilab

See Also:

• Ultra-Precise Quantum-Logic Clock Trumps Old Atomic Clock

Authors: Dave Mosher

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