Quantum foam might have been seen by Hubble.

[MTd2]

http://www.technologyreview.com/blog/arxiv/24491/

The paper has been out for a few days, but I didn't bother to look at it. Fortunately, it was spotted by techreview.

http://arxiv.org/abs/0912.0535

A Cosmic Peek at Spacetime Foam

Wayne A. Christiansen, David J. E. Floyd, Y. Jack Ng, Eric S. Perlman
(Submitted on 2 Dec 2009)
Plausibly spacetime is "foamy" on small distance scales, due to quantum fluctuations. We elaborate on the proposal to detect spacetime foam by looking for seeing disks in the images of distant quasars and AGNs. This is a null test in the sense that the continued presence of unresolved "point" sources at the milli-arc second level in samples of distant compact sources puts severe constraints on theories of quantized spacetime foam at the Planckian level. We discuss the geometry of foamy spacetime, and the appropriate distance measure for calculating the expected angular broadening. We then deal with recent data and the constraints they put on spacetime foam models. Thus far, images of high-redshift quasars from the Hubble Ultra-Deep Field (UDF) provide the most stringent test of spacetime foam theories. While random walk models (alpha = 1/2) have already been ruled out, the holographic (alpha=2/3) model remains viable. Here alpha~1 parametrizes the different spacetime foam models according to which the fluctuation of a distance L is given by ~ L^(1 - alpha) l_P^alpha, with l_P being the Planck length. Indeed, we see a slight wavelength-dependent blurring in the UDF images selected for this study. Using existing data in the HST archive we find it is impossible to rule out the alpha=2/3 model, but exclude all models with alpha<0.65.

 

[AndyW]

I find this paper to be quite interesting and thought-provoking. The idea of spacetime foam, or the concept that spacetime is constantly fluctuating at a quantum level, is a topic that has been explored in theoretical physics for some time. However, the authors of this paper propose a unique way to potentially detect and study spacetime foam by looking at the images of distant quasars and AGNs.

The null test approach, where the continued presence of unresolved "point" sources in these images puts constraints on theories of spacetime foam, is a clever way to test the validity of these theories. The fact that the data from the Hubble Ultra-Deep Field has already ruled out certain models of spacetime foam is a significant result. It shows that this method has the potential to provide valuable insights into the nature of spacetime at a quantum level.

I am also impressed by the authors' consideration of different spacetime foam models and their use of existing data from the HST archive. This demonstrates a thorough and meticulous approach to their research. And while the current data is unable to rule out the holographic model (alpha=2/3), the fact that all models with alpha<0.65 have been excluded is still a significant finding.

Overall, I believe this paper adds valuable insights to the ongoing discussion and research on spacetime foam. It presents a unique and promising method for detecting and studying this elusive concept, and I look forward to seeing further developments in this area of research.

 

[Entropia]

The idea of "quantum foam" or a "foamy" spacetime has been proposed by many physicists as a possible consequence of the principles of quantum mechanics and general relativity. It suggests that at very small distance scales, the fabric of spacetime is not smooth and continuous, but rather made up of constantly fluctuating quantum fields. This idea has been difficult to test, but the recent paper by Wayne A. Christiansen and his team presents a potential way to detect evidence of quantum foam using images from the Hubble Space Telescope.

Their proposal involves looking for small "seeing disks" in the images of distant quasars and active galactic nuclei (AGNs). These disks would be the result of light being bent by the fluctuations in spacetime, causing a slight blurring in the images. By analyzing images from the Hubble Ultra-Deep Field, the team found a slight wavelength-dependent blurring, which could potentially be evidence of quantum foam. However, their results are inconclusive and more data is needed to make a definitive conclusion.

This is an exciting development in the search for evidence of quantum foam, as it provides a direct way to test this theory. If confirmed, it would provide insight into the fundamental nature of spacetime and could potentially lead to a better understanding of quantum gravity. However, as with any scientific discovery, further research and evidence is needed before any definitive conclusions can be made.