January 10, 2013
Arizona Professor Challenges Popular Dark Energy Theory
[ Listen to the Podcast “The Search For Dark Energy” ]
redOrbit Staff & Wire Reports - Your Universe Online
A popular theory that relies on dark energy, thought to be the main contributor to the accelerating expansion of the Universe does not fit newly obtained data with regards to one fundamental constant — the proton to electron mass ratio.
Rodger Thompson, a University of Arizona astronomy professor, disclosed his findings Wednesday at the American Astronomical Society (AAS) meeting in Long Beach, California. He argues that dark energy theories, which have emerged as variations on Einstein´s theory of general relativity, do not support newly obtained results on the relative masses of protons and electrons during the earliest stages of the Universe.
He computed the ratio predicted by dark energy models, a hypothetical form of energy believed to be found throughout space, and found that these theories (which add a scalar field to Einstien´s equations to account for the acceleration o the Universe) did not fit the new data. Thompson´s findings “impact our understanding of the universe and point to a new direction for the further study of its accelerating expansion,” the university said in a recent statement.
In work that was honored with the 2011 Nobel Prize in Physics, researchers demonstrated that the expansion of the universe was speeding up, not slowing down, as had previously been thought. That acceleration could be accounted for by reinstating the “cosmological constant” into Einstein´s theory of General Relativity - originally introduced by Einstein to balance the expansion predicted by his original equations, as he believed at the time that the Universe was static.
“The constant was reinstated with a different value that produces the observed acceleration of the universe´s expansion. Physicists trying to calculate the value from known physics, however, get a number more than 10 to the power of 60 (one followed by 60 zeros) too large — a truly astronomical number,” the institution´s communications department said. “That´s when physicists turned to new theories of dark energy to explain the acceleration.”
“In his research, Thompson put the most popular of those theories to the test,” they said.
He focused on the value of a fundamental constant derived from the ratio of the proton and electron masses — a pure number with no units attached to it. Such fundamental constants shape the laws of physics, meaning that if the values change, then those laws will also have to change, and if they change by large amounts, it would radically alter the entire universe.
“The new physics model of dark energy that Thompson tested predicts that the fundamental constants will change by a small amount,” the university said. “Thompson identified a method of measuring the proton to electron mass ratio in the early universe several years ago, but it is only recently that astronomical instruments became powerful enough to measure the effect. More recently, he determined the exact amount of change that many of the new theories predict.”
“Last month, a group of European astronomers, using a massive radio telescope in Germany, made the most accurate measurement of the proton-to-electron mass ratio ever accomplished and found that there has been no change in the ratio to one part in 10 million at a time when the universe was about half its current age, around 7 billion years ago,” they added. “When Thompson put this new measurement into his calculations, he found that it excluded almost all of the dark energy models using the commonly expected values or parameters.”