For the first time, scientists measured the speed at which the force of gravity moves, one of the few remaining unmeasured fundamental constants of physics. The news, recently announced at a meeting of the American Astronomical Society, validates yet another of Einstein's theories.
Astronomers measured a slight \bending"" of radio waves as Jupiter passed in front of a distant quasar about nine billion light-years away, and determined that gravity's propagation speed is equal to the speed of light. While this was not groundbreaking news for scientists, it confirmed the long-standing assumptions about the property of gravity by an estimated equivalent width of five human hairs seen at 250 miles.
""Newton thought that gravity's force was instantaneous,"" said Dr. Sergei Kopeikin, a physicist at the University of Missouri in a New York Times report. ""Einstein assumed that it moved at the speed of light, but until now, no one had measured it.""
The measurement was conducted several months ago, using radio telescopes of the Very Long Baseline Array in the United States and Germany. The simultaneous observations of Jupiter by the telescopes provided the ability to detect the slightest deflection of radio waves caused by the planet's gravity.
Astronomers believe they have discovered some of the earliest known objects in the universe, including the most distant quasar ever found.
Scientists said the observations could provide important clues to how and when light began to emerge throughout the cosmos.
Two groups of researchers, using images from the Sloan Digital Survey and Hubble Space Telescope, detected faint light from over two dozen young galaxies and three quasars, at a distance of some 13 billion light-years. At the time the universe was less than a billion years old and apparently just emerging from an epoch of utter darkness.
In a recent interview with The New York Times, one of the team leaders, Dr. Xiaohui Fan of the University of Arizona, said ""These are the most distant and oldest known objects in the universe. They should tell us something of the evolution of the earliest quasars and black holes, and how the cosmic dark age ended.""
The current theory of the creation of the universe is that the Big Bang occurred about 14 billion years ago, and ever since the universe has cooled. Astronomers said that future Hubble observations could reveal an additional 500-1,000 new galaxies.
