One inconclusive experiment doesn't mean we're any closer to understanding the nature of space-time.
The world's first experiment designed to look for evidence that the universe exists as a hologram has found nothing to suggest that is the case.
But not-so-fast, Matrix naysayers: The result, published by researchers at the Department of Energy's Fermilab, is merely the first in a series of experiments designed to both show that we may be living in a hologram and to determine what type of hologram it is.
As you might expect, the details of one of the most advanced quantum mechanics experiments ever conducted are quite complex. But, basically, Fermilab scientist Craig Hogan is trying to determine the basic unit that makes up space-time. From an article about the theory we published earlier this year:
"Hogan says that you can imagine the universe around us as something of a television screen. If you zoom in far enough, you'll eventually start to see these 'pixels' where there is a lack of information. In other words, there could be a finite amount of 'data' that makes up the world, and when you get in close enough, you can see where the data starts to fail. Hogan is looking for that failure."
To look for this failure, Fermilab built the $2.5 million Holometer, which is a large device called an interferometer that blasts mirrors spaced apart in a long underground tube with lasers. As the mirrors move through time, Hogan explained earlier this summer, the lasers should be able to measure their position—any sort of jitteriness or uncertainty would suggest that space-time is not a continuum, Hogan told me.
"It means space and time aren't infinitely divisible, that they aren't a continuum. You can't divide the line into smaller and smaller points forever," Hogan said earlier this summer. "You get to the point where, like atoms, it's invisible. Except that invisible unit isn't even a unit of spacetime, it's a fundamental element of something that looks like spacetime when you have a lot of them together. It'd suggest that, when you dig down to some microscopic level, it's a quantum system."
So, that's what he was looking for. Fermilab announced Thursday that Hogan did not find what he was looking for. Does that mean his hypothesis is wrong? Not exactly.
"The first step to do is to do what we've already done, but do more of it—we need to run longer and look more sensitively," Hogan told me Friday, after the announcement of his experimental results. "This result is based only on about 150 hours of data, so in a few months we'll have a larger data set and we'll be able to nail it—maybe we'll have a more conclusive statement to make."
If he still sees no signal of quantum weirdness, that still doesn't mean that the nature of the universe isn't holographic. To be clear, we're not talking Princess Leia on an R2D2 projection hologram—Hogan is suggesting that what we see has, on a very tiny, quantum level, some weirdness and is by its nature imprecise. Therefore, what we see is more or less an interpretation of space-time units, whatever they may be.
There are several holographic hypotheses, and the Holometer is only set up right now to look at evidence that would suggest the universe is a hologram in what Hogan said is "the most obvious way."
"It could be a qualitatively different form of holographic jitter—instead of [spacetime] jittering back and forth, it could be a rotational jitter. If all of space were rotating, how could you tell?" he said. "Well, we can reconfigure the Holometer to do that but we have to change the paths of the light, which will take a couple years to set up."
Hogan says that even if he had gotten the results he was expecting, he wouldn't be trying to suggest that the universe isn't "real."
"A lot of the press coverage has emphasized the 'Do we live in a hologram,' aspect, which makes sense because of movies like The Matrix," he said. "Part of that is accurate—we are testing the idea that things are less independent than you thought, that things aren't as separate as something else in another place. We're not trying to prove that the three dimensional world is an illusion—it's obviously real. But the thing is there might be more behind it, a deeper level of connectivity we didn't know about."
Hogan has received some flack for even trying these experiments. As reported in Gizmodo, some of his fellow theoretical physicists believe the Holometer is a flawed experiment:
"Expect to see a bit of schadenfreude making the rounds of the theoretical physics community today. As Sabine Hossenfelder, a physicist at Nordita in Sweden and one of the more outspoken critics of the experiment, tweeted: 'Holometer results are out: Nothing. Not surprising, as the idea underlying it is nonsense.'"
As you'd expect, Hogan disagrees, and in talking to him, he sounds quite glad that his theoretical forebearers have left him with enough theories to test and that he's able to do this work at all.
"I can't say I'm disappointed," he said. "We had a machine doing the experiment we wanted which was the idea, we're doing a quantum experiment on space-time, testing the relationship between quantum mechanics and and the theory of relativity. I think that's to me, the physics message I want people to take away."
"Of course it would have been unbelievably exciting to make a discovery in the first round," he added. "Probably literally incredible to most of my colleagues. This is the best thing about doing science. It's a real exploration of the nature of the universe."