Princeton Scientists Say Einstein’s Theory Applies Beyond the Solar System
by Kitta MacPherson
Princeton University scientists (from left) Reinabelle Reyes, James Gunn and Rachel Mandelbaum led a team that analyzed more than 70,000 galaxies and demonstrated that the universe -- at least up to a distance of 3.5 billion light years from Earth -- plays by the rules set out by Einstein in his theory of general relativity. (Photo: Brian Wilson)
A team led by Princeton University scientists has tested Albert Einstein’s theory of general relativity to see if it holds true at cosmic scales. And, after two years of analyzing astronomical data, the scientists have concluded that Einstein’s theory, which describes the interplay between gravity, space and time, works as well in vast distances as in more local regions of space.
The scientists’ analysis of more than 70,000 galaxies demonstrates that the universe — at least up to a distance of 3.5 billion light years from Earth — plays by the rules set out by Einstein in his famous theory.
Ever since the physicist Arthur Eddington measured starlight bending around the sun during a 1919 eclipse and proved Einstein’s theory of general relativity, the scientific world has accepted its tenets. But until now, according to the team, no one had tested the theory so thoroughly and robustly at distances and scales that go beyond the solar system.
Reinabelle Reyes, a Princeton graduate student in the Department of Astrophysical Sciences, along with co-authors Rachel Mandelbaum, an associate research scholar, and James Gunn, the Eugene Higgins Professor of Astronomy, outlined their assessment in the March 11 edition of Nature. (more…)
Curvature of Space Measurement Step Toward Uniting Gravity Theory with Quantum Theory
Sun's path in the sky in front of quasars, 2005.
Scientists using a continent-wide array of radio telescopes have made an extremely precise measurement of the curvature of space caused by the Sun’s gravity, and their technique promises a major contribution to a frontier area of basic physics.
“Measuring the curvature of space caused by gravity is one of the most sensitive ways to learn how Einstein’s theory of General Relativity relates to quantum physics. Uniting gravity theory with quantum theory is a major goal of 21st-Century physics, and these astronomical measurements are a key to understanding the relationship between the two,” said Sergei Kopeikin of the University of Missouri.
Kopeikin and his colleagues used the National Science Foundation’s Very Long Baseline Array (VLBA) radio-telescope system to measure the bending of light caused by the Sun’s gravity to within one part in 30,000. With further observations, the scientists say their precision technique can make the most accurate measure ever of this phenomenon. (more…)
New Gravity-Wave Probe Searches for Big Bang Radiation
The QUIET experiment in operation in the Atacama Desert. The receiver in the mount on the roof of the building rapidly scans the sky, looking for radiation emitted shortly after the birth of the universe.
A tiny fraction of a second following the big bang, the universe allegedly experienced the most inflationary period it has ever known.
During this inflationary era, space expanded faster than the speed of light. It sounds crazy, but it fits a variety of cosmological observations made in recent years, said University of Chicago physicist Bruce Winstein.
“Theorists take it to be true, but we have to prove it,” said Winstein, the Samuel K. Allison Distinguished Service Professor in Physics at the University of Chicago. “It needs a real test, and that test is whether or not gravity waves were created.” (more…)
The Day The Universe Froze - Accounting for Dark Energy
By David F. Salisbury
Research Associate Sourish Dutta and Professor of Physics Robert Scherrer at Vanderbilt University.
Imagine a time when the entire universe froze. According to a new model for dark energy, that is essentially what happened about 11.5 billion years ago, when the universe was a quarter of the size it is today.
The model, published online May 6 in the journal Physical Review D, was developed by Research Associate Sourish Dutta and Professor of Physics Robert Scherrer at Vanderbilt University, working with Professor of Physics Stephen Hsu and graduate student David Reeb at the University of Oregon.
A cosmological phase transition – similar to freezing – is one of the distinctive aspects of this latest effort to account for dark energy – the mysterious negative force that cosmologists now think makes up more than 70 percent of all the energy and matter in the universe and is pushing the universe apart at an ever-faster rate. (more…)
Satellite Measures the Earth’s Gravity Field to Map Ocean Topography
Earth Survey Satellite GOCE (© Astrium GmbH / Mathias Pikelj)
The Earth explorer satellite GOCE (Gravity Field and Steady-State Ocean Circulation Explorer), built by the European Space Agency ESA, was successfully launched today at 15:21 GMT from the Russian Cosmodrome Plesetsk. GOCE is the first satellite mission within the framework of the Living Planet Programme of ESA and will map Earth’s gravity field in unprecedented detail.
From the data obtained, the GFZ - German Research Centre for Geosciences will calculate its own, high resolution gravity field. “The accuracy of the depiction of the Earth’s gravity field, well known as the ‘Potsdam Gravity Potato’ will now be enhanced by orders of magnitude”, says Prof. Dr. Hüttl, Scientific Executive Director of the GFZ. The GFZ, which looks back on many years of experience in analysis of satellite-based gravity field, measurements participates in the evaluation of GOCE data as a co-operating partner within the framework of the so called High Level Processing Facility (HPF) under the Project Managment of the Technical University Munich and together with scientific institutions from Germany, France, Denmark, Italy, Austria, Switzerland and the Netherlands. (more…)
March Launch Planned for ESA’s Gravity Mission
The GOCE satellite undergoing testing at the Russian Plesetsk Cosmodrome in August 2008. (ESA)
ESA is now gearing up to return to Russia to oversee preparations for the launch of its GOCE satellite – now envisaged for launch on 16 March 2009. This follows implementation of the corrective measures after the anomaly with the Rockot launcher that delayed the launch of GOCE by Eurockot Launch Services last October.
An advance party from ESA has just arrived at the Plesetsk Cosmodrome in northern Russia to arrange logistical matters while the team of engineers will arrive in mid-February.
The five metre-long GOCE (Gravity field and steady-state Ocean Circulation Explorer) satellite has been in storage at the launch site since last October. Once the team of ESA and Thales Alenia Space engineers arrive, work will begin preparing the satellite for launch. As prime contractor, Thales Alenia Space has led an all-European consortium of over 40 companies to build the GOCE satellite.
ESA’s GOCE Project Manager Danilo Muzi commented that, “The team are really eager to resume the launch campaign and to finish the job interrupted last autumn. The launch in a few weeks time will be the deserved reward for all their efforts.” (more…)
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