From: University of Alabama-Huntsville
Posted: Thursday, February 6, 2003
The sharp image of a galaxy halfway across the universe might shred modern theories about the structures of time and space, and change the way astrophysicists view the "Big Bang," according to two scientists at The University of Alabama in Huntsville (UAH).
Their findings might also provide important clues to (and cause significant upheaval among) researchers trying to merge two of the most significant scientific theories of the last century: Einstein's theory of general relativity and Planck's theory of the quantum.
Using Hubble Space Telescope images of galaxies at least four billion light years from Earth, UAH's Dr. Richard Lieu and Dr. Lloyd Hillman tested a popular theory of modern quantum physics: That time flows in incredibly small but finite and measurable quantum bits.
Their research findings are scheduled to be published in the March 10 edition of "Astrophysical Journal Letters," and have been released in the journal's website.
Lieu and Hillman used images gathered by the Hubble Space Telescope to look for patterns that shouldn't be present if prevailing notions of time quantum were correct.
"I fully anticipated that the pattern wouldn't show," said Lieu, an associate physics professor at UAH.
Instead, when they looked at Hubble images of galaxies at least four billion light years from Earth, each image unexpectedly showed a sharp interferometric pattern -- a ring around the galaxy.
Using that data, the UAH team was able to determine that the speed of that light didn't fluctuate by more than a few parts in 10^-32 as it traveled across the cosmos. That measurement is significantly more accurate than should be possible if quantum theories of time and space are correct.
Their findings will create problems for astrophysicists and cosmologists who agree with Albert Einstein's theory that time, gravity and the fabric of space are different manifestations of the same phenomenon, sort of like thunder and light are different signatures of lightning. More recently, when scientists theorized that gravity is composed of quantum energy "packets" called gravitons, it made sense that time and space would also be composed of related quantum bits.
Which brings us to Planck time and Planck length, thought to be the shortest possible measurements of time and distance. Both are based on calculations of the most energetic radiation theoretically possible. There are twenty million trillion, trillion, trillion Planck time intervals (5x10^-44) in one second. Planck length is the distance a beam of light would travel in that time -- about 0.000000000000000000000000000000001 (10^-33) cm.
Tying together the theory of gravitons with the shortest possible measurements of time, quantum theory says time would move in miniscule, Planck time-sized bits -- like grains of sand passing chaotically through an hourglass, or a sequence of jittery freeze frames that on average last one Planck time rather than a continuous, seamless flow.
Scientists say time and distances smaller than Planck scales are "fuzzy," since they can't be measured. If there is a finite limit to the smallest units of time and distance, however, that means there are limits on how accurately scientists can measure things like the speed of light.
This limitation opens the possibility of Planck-scale fluctuations in the speed of light, said Lieu. Because these fluctuations would be extremely small, however, they would only be evident in light that travels a great distance. The extended travel gives the slightest variations in speed an opportunity to spread out and become noticeable.
(The same principle applies to racing events. A sprinter, for instance, one percent faster than his opponents might win a 100-meter race in a photo finish, while a marathon runner one percent faster than the field would finish a race hundreds of meters ahead.)
After billions of years, the faster components of a light wave would be far enough ahead and the slower components far enough behind that the light's wave front would be sufficiently distorted (or blurred) to be seen and measured by a telescope.
It was that distortion that Lieu and Hillman expected to find in the Hubble images. Not finding that distortion means time isn't a quantum function, says Lieu, and that time might flow fluidly and precisely at intervals infinitely smaller than Planck time.
"If time doesn't become 'fuzzy' beneath a Planck interval, this discovery will present problems to several astrophysical and cosmological models, including the Big Bang model of the universe," said Lieu. "The Big Bang theory supposes that at the instant of creation, the quantum singularity that became the universe would need to have infinite density and temperature. To avoid that sticky problem, theorists invoked the Planck time. They said if the instant of creation was also a quantum event, when space and time were both blurry, then you don't need infinite density and temperature at the start of the Big Bang.
"If time moves along like business as usual even at Planck scales, however, you have to reconcile the Big Bang model with an event that isn't just off the scale, it's infinite!"
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