For the second time in as many months, images gathered by the Hubble Space Telescope (HST) are raising questions about the structures of time and gravity, and the fabric of space.
Using two HST images, astronomers from Italy and Germany looked for but did not find evidence supporting a prevailing scientific theory that says time, space and gravity are composed of tiny quantum bits.
Using existing theories, the team led by Dr. Roberto Ragazzoni from the Astrophysical Observatory of Arcetri, Italy, and the Max Planck Institute for Astronomy in Heidelberg, Germany, calculated that infinitesimally small quantum-scale variations in space time would blur images of galaxies seen from vast distances across the universe.
Instead, when they looked at both diffraction patterns from a supernova and the raw image of a second galaxy more than five billion light years from Earth, they saw images much sharper than should be possible if quantum-scale phenomenon operated as previously supposed.
Their research is scheduled to be published in the April 10, 2003, edition of Astrophysical Research - Letters.
"The basic idea is that space time should fluctuate," said Ragazzoni. "If you are looking at light from a huge distance, this light passing through space time would be subject to this fluctuation in space time. They should give a distorted image of the far universe, like a blurring.
"But you don't see a universe that is blurred. If you take any Hubble Space Telescope deep field image you see sharp images, which is enough to tell us that the light has not been distorted or perturbed by fluctuations in space time from the source to the observer. This observation is enough to rule out this effect on the quantum scale.
"You can say," said Ragazzoni, "that this measurement constrains the quantum gravity theory to certain parameters."
This report comes a month after physicists at The University of Alabama in Huntsville (UAH) announced their unsuccessful attempt to use an image from an HST interferometer to find evidence of Planck-scale effects. Taken together, the independent research findings might force physicists to reexamine the scientific underpinnings of the quantum theories of gravity, time and space.
To look for the quantum blurring effect the European team used a parameter from optics, the Strehl ratio, to calculate how sharply the telescope should be able to resolve an image of the distant light source and its first Airy ring - a signature of the interference of the rays of light entering a telescope.
If the popular quantum theories were correct, space-time effects should blur light from distant sources beyond the telescope's ability to resolve them.
"Without a theory to describe this, I think it's hard not to agree that it is time to start to consider theories that do not require this Planck scale, at least not like it is now," said Ragazzoni. "From an experimental point of view, there is no establishment. We are proud to have established in as rigorous a manner as possible the parameters of this quantum effect."
The Planck-scale quantum theories of time, space and gravity were derived from attempts to calculate the theoretical limits to electromagnetic energy, according to a UAH physicist, Dr. Richard Lieu.
By inverting Albert Einstein's theory of relativity (E=mc2 becomes m=E/c2), physicists could calculate how much mass should be added to a photon as it gains energy. Using that, they calculated a theoretical limit to how much energy a photon might contain before gaining so much mass it would collapse into a photon-sized black hole.
That theoretical upper limit was then used to set theoretical limits on time. One cycle of a photon carrying that much energy would last 5 x 10-44 seconds, an interval called Planck time. As the shortest potentially-measurable interval of time, theorists speculated that time moves is Planck time-sized quantum bits.
In his theory of general relativity, Einstein theorized that time, space and gravity are different manifestations of the same phenomenon, much as light and thunder are signatures of the electrical discharge in lightning. If time is made up of quantum bits, that would also mean space and gravity should also be composed of quantum units.
Since the expected blurring "signature" of quantum space time isn't seen, however, it might mean that time isn't made of quantum bits, and neither are space or gravity.
Instituto Nazionale di Astrofisica
INAF, Astronomical Observatory of Padova
Max Planck Institut fuer Astronomie
University of Alabama in Huntsville
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