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Why Our Universe is Not a Hologram

Superstrings may exist in 11 dimensions at once. Via National Institute of Technology Tiruchirappalli.

Superstrings may exist in 11 dimensions at once. Via National Institute of Technology Tiruchirappalli.

Editor’s note: This article was originally published by Brian Koberlein on G+, and it is republished here with the author’s permission.

There’s a web post from the Nature website going around entitled “Simulations back up theory that Universe is a hologram.” It’s an interesting concept, but suffice it to say, the universe is not a hologram, certainly not in the way people think of holograms. So what is this “holographic universe” thing?

It all has to do with string theory. Although there currently isn’t any experimental evidence to support string theory, and some evidence pointing against it, it still garners a great deal of attention because of its perceived theoretical potential. One of the theoretical challenges of string theory is that it requires all these higher dimensions, which makes it difficult to work with.

In 1993, Gerard t’Hooft proposed what is now known as the holographic principle, which argued that the information contained within a region of space can be determined by the information at the surface that contains it. Mathematically, the space can be represented as a hologram of the surface that contains it.

That idea is not as wild as it sounds. For example, suppose there is a road 10 miles long, and its is “contained” by a start line and a finish line. Suppose the speed limit on this road is 60 mph, and I want to determine if a car has been speeding. One way I could do this is to watch a car the whole length of the road, measuring its speed the whole time. But another way is to simply measure when a car crosses the start line and finish line. At a speed of 60 mph, a car travels a mile a minute, so if the time between start and finish is less than 10 minutes, I know the car was speeding.

A visualization of strings. Image credit: R. Dijkgraaf.

A visualization of strings. Image credit: R. Dijkgraaf.

The holographic principle applies that idea to string theory. Just as its much easier to measure the start and finish times than constantly measure the speed of the car, it is much easier to do physics on the surface hologram than it is to do physics in the whole volume. The idea really took off when Juan Martín Maldacena derived what is known as the AdS/CFT correspondence (an arxiv version of his paper is here ), which uses the holographic principle to connect the strings of particle physics string theory with the geometry of general relativity.

While Maldacena made a compelling argument, it was a conjecture, not a formal proof. So there has been a lot of theoretical work trying to find such a proof. Now, two papers have come out (here and here) demonstrating that the conjecture works for a particular theoretical case. Of course the situation they examined was for a hypothetical universe, not a universe like ours. So this new work is really a mathematical test that proves the AdS/CFT correspondence for a particular situation.

From this you get a headline implying that we live in a hologram. On twitter, Ethan Siegel proposed a more sensible headline: “Important idea of string theory shown not to be mathematically inconsistent in one particular way”.

Of course that would probably get less attention.


Brian Koberlein is an astrophysicist and physics professor at Rochester Institute of Technology. He writes about astronomy and astrophysics on his blog One Universe at a Time, as well as on Google+. You can follow him on YouTube, and on Twitter @BrianKoberlein.

Comments on this entry are closed.

  • Art Riechert December 14, 2013, 10:47 PM

    People who have NDEs describe them in terms that corroborate the holographic universe theory and that sound like they were on the holographic film rather than the projection from that film. They say things like “I literally felt like I was everywhere in the Universe at once” and “I felt an overwhelming sense of oneness and connectedness” and “it seemed even more real than normal” or “realer than real” which refers to Craig Hogan’s statement that there is a certain inherent blurriness or fuzziness in a holographic projection and since they were on the original film rather than living on the projection which is what our Universe is supposed to be it makes sense that it would be “realer than real.” They also say things like “I had all knowledge” which is a reference to the connectedness of a piece of holographic film.

    • jameskrug December 18, 2013, 11:15 AM

      That’s a very creative connection to make. Science tends to shy away from things deemed “paranormal”, but I think there are certainly very relevant, scientifically eye-opening explanations for almost all of these phenomena, which could greatly expand our knowledge of the universe if taken seriously.

  • magic3499 December 15, 2013, 2:44 AM

    Geez, after reading the comments, I hope there’s no sequel.

  • IVAN3MAN_AT_LARGE December 16, 2013, 8:25 PM

    “boorreetoes”? You mean burritos. Your dog probably ate it!

    • daniel_rey_m December 17, 2013, 9:13 AM

      Ivanman, I’m sorry but you had better find another explanation.
      I have no pets, other than several corner spiders in a dusty, unruly household full of cardboard boxes that looks more like a warehouse. Over the years I’ve managed to develop an efficient way of feeding them, and THIS, TOO, IS RELEVANT for the said theory. One must use a big jar to capture certain
      insects, like cloth moths, mosquitos and big flies, and a small one for the tiny flies, which come in three varieties. If you’re lucky you’ll find them resting on a wall. It’s almost impossible to trap them on the wing as they fly back and forth, no matter how large the mouth of the jar, especially in the case of the moths, whose movements are too quick and erratic when they’re airborne. Once they’re safely in the jar, shake it until the thing is groggy but not knocked out. This is essential since 1) most spiders will reject a dead body, and 2) if you don’t shake, the bug will escape when you open and try to drop it onto the web. There are more complications but I can’t go into this more deeply. All I will say is that, having shaken cautiously as explained, you might open the jar AND FIND NOTHING IN IT, as though the animal had slipped through a portal straight into the twilight zone. I challenge you to explain that without
      involving the dogs this time around.

  • AD December 17, 2013, 11:53 PM

    Wow, thanks for explaining it (and disappointing the [Deleted.] out of me, lol). But it’s also reassuring, because the thought of not being real is a hard thought to sit and bare.

    I’m curious though, does the “life is a simulation” theory as a whole apply to this paper? Or was this paper simply not proof of that particular theory at all? It seems like the theory hasn’t been disproved, simply that they completely misled you in the title. They made you believe it was about the “life is a simulation” theory or the “simulation hypothesis” I think it’s called, but this seems almost entirely unrelated.

    edit: When I say paper, I don’t mean your article, but the paper/s you’re talking about.

  • jameskrug December 18, 2013, 7:59 AM

    I find it a tad ironic that there are now hundreds of thousands of credible UFO reports from around the world, spanning decades. Yet this idea is still generally scoffed upon by mainstream science. Yet, there is still zero observational evidence of string theory, and yet it is pursued with vigor. You stay consistent, scientific method!

  • Caihlyn December 21, 2013, 10:02 PM

    Biological life forms are limited by their three spatial dimensions plus linear time. If there was a way to peer into the higher dimensions I think many mysteries would be explained.