You may have read today that the entire universe is a giant hologram. Maybe your mind was blown while you contemplated a 2D universe, or that researchers had somehow found substantial evidence you were "living in an illusion".
Image: NASA/WMAP Science Team/Wikimedia Commons
No, nope. Not what happened. Rather, physicists figured out that one of their models doesn't break when they apply data from the real universe. Which is still awesome, but not insane.
Theoretical physicists try to understand the Big Bang and how the universe ended up the way it is today. One theory scraps a spatial dimension to better describe the strange behaviour of the early universe. Now, an international group of physicists found they could recreate actual physical data collected on our universe using this 2D holographic model.
"It's holographic in the sense that there's a description of the universe based on a lower dimensional system consistent with everything we see from the Big Bang," Niayesh Afshordi, the study's first author from the University of Waterloo in Canada, told Gizmodo.
Unfortunately, the theory explaining how massive things work, general relativity, doesn't fit nicely with the theory of how tiny things work, quantum mechanics. That especially sucks when you're trying to describe the early universe, where literally all mass and energy was balled up in a tiny space. One theory trying to reconcile the two, quantum gravity, says that if you ditch a spatial dimension, you can also ditch gravity in your calculations to make things easier.
The researchers built a model with one time and two space dimensions from this insight, and plugged in real data on the universe, including cosmic microwave background (CMB), invisible light from several hundred thousand years after the Big Bang that hits Earth from all directions. The model accurately recreated the behaviour of thin slices of the CMB, but cannot recreate slivers of the universe more than 10 degrees wide, which would require a more complex model. Afshordi explained the scientists didn't prove that the early universe was a hologram, but rather, found that they couldn't rule out holographic models. They published their results in the journal Physical Review Letters on Friday.
Image: Paul McFadden
Other researchers were intrigued by the results, but pointed out that the holographic model isn't preferred over the standard models of cosmology that scientists currently use to study both the present universe and the universe around the time of the Big Bang. "In that sense, the result is inconclusive in that it does not allow you to rule out their holographic model," Daniel Grumiller, physicist at the Institute for Theoretical Physics at the Vienna University of Technology, told Gizmodo, but "neither does it allow to make a statement that the data would prefer their holographic model over standard cosmology".
And finally, somehow, no one else seemed to ask the researchers the most important question: Does the model say that we're living in a hologram? "I would say you don't live in a hologram, but you could have come out of a hologram," said Afshordi. After all, the theory intends to describe the early universe. If there was a time when the universe had only two spatial dimensions, it's not clear when switch would have happened, or what things would be like if you could travel back in time.
As for the universe in 2017, Ashfordi himself told me: "There are definitely three dimensions."