The holographic universe, an idea born out of the seemingly endless quest to reconcile our understanding of gravity with the other fundamental forces of nature, has raised its head again, with the claim that 鈥渟ignificant evidence鈥� has been found that we live in a hologram.
The notion of a holographic universe comes from a mathematical quirk buried in string theory, which is our leading attempt at a theory of everything.
This quirk says that within a particular kind of cosmos, we can effectively do away with troublesome gravity by reducing the number of dimensions in our mathematical description by one. You can think about the resulting universe as information 鈥減ainted鈥� over a 鈥渃osmological surface鈥�, which then permeates into other dimensions, creating the physical cosmos 鈥� akin to a hologram, a 3D image created from information in a 2D pattern.
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The result of the holographic principle would be that gravity and our third spatial dimension could be regarded as 鈥渋llusions鈥�.
While recent calculation has , the question on everyone鈥檚 lips is, 鈥淗ow would we know?鈥� Unfortunately, our day-to-day experience, with three dimensions of space and one of time, would be the same whether the universe was holographic or not, and we have to look into the realm of the quantum to try to see its impact. But all is not lost. Various attempts are being made to do just this.
Embryonic universe
And so to the latest for this strange reality. These spring from a paper that worries about the fuzziness of space and time, not now, but in the initial instants of the universe (, DOI: 10.1103/PhysRevLett.118.041301).
In our standard cosmological model, the embryonic universe has a particular pattern of fluctuating energy, like the ripples on a pond. In the rival holographic universe model, the pattern of these energy ripples is different. In both kinds of universe, these energy fluctuations are accentuated by the expansion of the universe and are seen on the sky we observe today as the cosmic microwave background (CMB) radiation, captured in fine detail by the .
Just how 鈥渟ignificant鈥� is the evidence in this research for the holographic universe? Looking beyond the headlines, the significance is less clear, and the best that can be said is that the theory does as well as our standard model in accounting for some of the observations of the CMB, but does a poorer job when considering all CMB data.
What this really amounts to is that the idea of a holographic universe is not dead, as current observations don鈥檛 rule it out, but it does stand on shaky ground compared with the standard model.
However, as the study authors note, calculating the ripples in the early universe is not a simple task, and future mathematics may yet lead to a better fit to observations and point to us living in a holographic universe. The true nature of our universe is still up for grabs.
