How to Measure Quantum Foam With a Tabletop Experiment

How to Measure Quantum Foam With a Tabletop Experiment: Bekenstein's goal is to move the block by a distance that is about equal to the Planck length. His method is simple: zap the block with a single photon.

The photon carries a small amount of moment and consequently pushes the block as it enters the glass, giving it some momentum.  As the photon leaves the block, the block comes to rest.

So the result of the photon's passage is that it moves the block a small distance.

Bekenstein's idea is that if this distance is smaller than the Planck length, then the block cannot move and the photon cannot pass through it.

So the experiment involves measuring the number of photons that pass through the block. If the number is fewer than predicted by classical optics, then that proves the existence of quantum foam.

Physicists propose test for loop quantum gravity

Physicists propose test for loop quantum gravity: Now in a new study, scientists have found that, when black holes evaporate, the radiation they emit could potentially reveal “footprints” of loop quantum gravity, distinct from the usual Hawking radiation that black holes are expected to emit....
In their study, the scientists have used algorithms to show that primordial black holes are expected to reveal two distinct loop quantum gravity signatures, while larger black holes are expected to reveal one distinct signature. These signatures refer to features in the black hole’s energy spectrum, such as broad peaks at certain energy levels.
Using Monte Carlo simulations, the scientists estimated the circumstances under which they could discriminate the predicted signatures of loop quantum gravity and those of the Hawking radiation that black holes are expected to emit with or without loop quantum gravity. They found that a discrimination is possible as long as there are enough black holes or a relatively small error on the energy reconstruction.

Black Hole Mass Must Be Quantized, Say Physicists - Technology Review

Black Hole Mass Must Be Quantized, Say Physicists - Technology Review: If black hole mass is not quantised, then the mass could take essentially any value. And if that were the case, the rate of production of micro black holes would be infinite: they could form in any collision, at any energy.

Since that's clearly not the case, the masses of micro black holes must be quantised.

That immediately raises a number of important questions, not least of which is what governs black hole quantisation.

Distant light hints at size of space-time grains - space - 07 July 2011 - New Scientist

Distant light hints at size of space-time grains: terrestrial telescopes... have seen low-energy photons from a gamma-ray burst (GRB) arriving before their high-energy counterparts. While this could be due to delays in emission at the source, it could also be caused by the interaction of photons with the structure of space-time...
Now a team has used data from the Integral satellite, run by the European Space Agency (ESA), to study an entirely different effect: the polarisation of light of different energies from a GRB...
this puts an important limit on the size of the grains of space-time. According to an ESA press release, it means they must be smaller than 10-48 metres, many orders of magnitude smaller than the Planck length of 10-35 metres, the universe's smallest length scale...

Fractal Dimensions Should Modify The Casimir Effect - Technology Review

Fractal Dimensions Should Modify The Casimir Effect - Technology Review: Cheng says that if the distance between the plates is about the same as the scale of any extra dimension, then this must effect the Casimir force too. In fact, he says that this force will be stronger if the extra dimension is integral than if it is fractal but that the exact nature of the difference is sensitive to the fractal degree.

Scientists suggest spacetime has no time dimension

Scientists suggest spacetime has no time dimension: The researchers give an example of this concept of time by imagining a photon that is moving between two points in space. The distance between these two points is composed of Planck distances, each of which is the smallest distance that the photon can move. (The fundamental unit of this motion is Planck time.) When the photon moves a Planck distance, it is moving exclusively in space and not in absolute time, the researchers explain. The photon can be thought of as moving from point 1 to point 2, and its position at point 1 is “before” its position at point 2 in the sense that the number 1 comes before the number 2 in the numerical order. Numerical order is not equivalent to temporal order, i.e., the number 1 does not exist before the number 2 in time, only numerically.
As the researchers explain, without using time as the fourth dimension of spacetime, the physical world can be described more accurately. As physicist Enrico Prati noted in a recent study, Hamiltonian dynamics (equations in classical mechanics) is robustly well-defined without the concept of absolute time. Other scientists have pointed out that the mathematical model of spacetime does not correspond to physical reality, and propose that a timeless “state space” provides a more accurate framework.

Out Of The Fabric - Science News

Out Of The Fabric - Science News: Further study of spaceless theories may help solve serious problems confronting physicists today, Seiberg believes. String theory implies countless possible vacuum states — that is, spaces of differing physical properties — with no obvious method for determining which one the visible universe should have chosen. Knowing how space emerges from spacelessness might help explain why humans exist in one particular space from among the countless possibilities.

Doing away with time poses more difficult problems, Seiberg acknowledges. Basic notions in physics, such as that of causes preceding effects, or predicting the outcome of experiments before the experiment is done, seem to lose their meaning if there is no time to define before and after. So some physicists, Markopoulou for one, have suggested that even if space is emergent, time may remain fundamental. In fact, she conjectures, time is needed to allow quantum processes to create the illusion of space. Space may not have been around at the beginning, but that beginning would be stillborn without time to get reality going.

Doubly special relativity

Doubly special relativity: It turns out that at the Planck scale e = m, even though at macro scales e=mc2. And at the Planck scale, a Planck mass is 2.17645 × 10-8 kg – supposedly the mass of a flea’s egg – and has a Schwarzschild radius of a Planck length – meaning that if you compressed this mass into such a tiny volume, it would become a very small black hole containing one Planck unit of energy.
To put it another way, at the Planck scale, gravity becomes a significant force in quantum physics. Although really, all we are saying that is that there is one Planck unit of gravitational force between two Planck masses when separated by a Planck length – and by the way, a Planck length is the distance that light moves within one unit of Planck time!
And since one Planck unit of energy (1.22×1019 GeV) is considered the maximal energy of particles – it’s tempting to consider that this represents conditions expected in the Planck epoch, being the very first stage of the Big Bang.

Our world may be a giant hologram

http://www.newscientist.com/article/mg20126911.300-our-world-may-be-a-giant-hologram.html