The holographic principle of the universe has been a popular theory among crazies and string theorists for years.

In a larger and more speculative sense, the theory suggests that the entire universe can be seen as a two-dimensional information structure “painted” on the cosmological horizon, such that the three dimensions we observe are only an effective description at macroscopic scales and at low energies. Cosmological holography has not been made mathematically precise, partly because the cosmological horizon has a finite area and grows with time.^{[2]}^{[3]}

Take a look at the back of a credit card. You can see the metallic two-dimensional sticker on the back, right? When you tilt it back and forth, the image on the sticker appears to be three-dimensional as light reflects off of it in the changing light. The holographic prinicple of the universe says that this is how the universe behaves: the entire universe is two-dimensional and we only perceive it to be three dimensional because of a quirk of light, but also that we’re incapable of recognizing the holography of the universe as a result of the precision of the hologram (much like a *really* convincing 3D movie that you’ve been watching your whole life).

The idea that spacetime may not be entirely smooth – like a digital image that becomes increasingly pixelated as you zoom in – had been previously proposed by Stephen Hawking and others. Possible evidence for this model appeared last year in the unaccountable “noise” plaguing the GEO600 experiment in Germany, which searches for gravitational waves from black holes. To Hogan, the jitteriness suggested that the experiment had stumbled upon the lower limit of the spacetime pixels’ resolution.

The universe is probably not smooth. This has been theorized since the days of Max Planck around the turn of the last century and today the supposed graininess of the universe is relatively well-accepted, as far as new and crazy/mind-blowing/debilitating theories go.

Proponents of this theory have long been resigned to the ranks of stoner philosophy majors going on about how *the universe is totally flat, man, totally. *In the background, though, theorists have been refining the theory and now it’s time for them to shine.

“So we want to build a machine which will be the most sensitive measurement ever made of spacetime itself,” says Hogan. “That’s the holometer.”

…

The holometer’s precision means that it doesn’t have to be large; at 40 meters in length, it is only one hundredth of the size of current interferometers, which measure gravitational waves from black holes and supernovas. Yet because the spacetime frequencies it measures are so rapid, it will be more precise over very short time intervals by seven orders of magnitude than any atomic clock in existence.

The results from this experiment will likely be a hot topic of debate for a long time, but if a definitive answer is shown then it could revolutionize not only the field of quantum mechanics, but physics as a whole.

(via fuckyeahphysics)

Model describes universe with no big bang, no beginning, and no end

By suggesting that mass, time, and length can be converted into one another as the universe evolves, a new study has proposed a new class of cosmological models that may fit observations of the universe better than the current big bang model.

Wun-Yi Shu, an associate professor at National Tsing Hua University in Taiwan, explains that the new models emerge from a new perspective of some of the most basic entities: time, space, mass, and length. In his proposal, time and space can be converted into one another, with a varying speed of light as the conversion factor. Mass and length are also interchangeable, with the conversion factor depending on both a varying gravitational “constant” and a varying speed of light (G/c²).

Basically, as the universe expands, time is converted into space, and mass is converted into length. As the universe contracts, the opposite occurs.

The speed of light is simply a conversion factor between time and space in spacetime. It is simply one of the properties of the spacetime geometry. Since the universe is expanding, the conversion factor somehow varies in accordance with the evolution of the universe, hence the speed of light varies with cosmic time.

The newly proposed models have four distinguishing features:

- The speed of light and the gravitational “constant” are not constant, but vary with the evolution of the universe.
- Time has no beginning and no end; i.e., there is neither a big bang nor a big crunch singularity.
- The spatial section of the universe is a 3-sphere [a higher-dimensional analogue of a sphere], ruling out the possibility of a flat or hyperboloid geometry.
- The universe experiences phases of both acceleration and deceleration.

The models were tested against current cosmological observations of Type Ia supernovae that have revealed that the universe appears to be expanding at an accelerating rate. Because acceleration is an inherent part of this model, it fits the redshift data of the observed supernovae quite well. In contrast, the currently accepted big bang model does not fit the data, which has caused scientists to search for other explanations such as dark energy that theoretically makes up 75% of the mass-energy of the universe.

The new models may also account for other problems faced by the standard big bang model. For instance, the flatness problem arises in the big bang model from the observation that a seemingly flat universe such as ours requires finely tuned initial conditions. But because the universe is a 3-sphere in this models, the flatness problem “disappears automatically.”

Similarly, the horizon problem occurs in standard cosmology because it should not be possible for distant places in the universe to share the same physical properties (as they do), since it should require communication faster than the speed of light due to their great distances. However, the models solve this problem due to their lack of big bang origin and intrinsic acceleration.

Essentially, this work is a theory about how the magnitudes of the three basic physical dimensions, mass, time, and length, are converted into each other, or equivalently, a theory about how the geometry of spacetime and the distribution of mass-energy interact.

**Source:** PhysOrg.com | Read the full story at The Physics ArXiv Blog

The paper is available via arXiv.org