Historical research guide · 0535 · 2016
A test of general relativity using the LARES and LAGEOS satellites and a GRACE Earth gravity model
Ignazio Ciufolini · Antonio Paolozzi · Erricos C. Pavlis · Rolf Koenig · John Ries · Vahe Gurzadyan · Richard Matzner · Roger Penrose · Giampiero Sindoni · Claudio Paris · Harutyun Khachatryan · Sergey Mirzoyan
In one minute
Frame-dragging is general relativity’s prediction that a spinning mass pulls spacetime around with it, so that the Earth, simply by turning, twists the reference frames a satellite orbits inside. Ciufolini, Paolozzi, Pavlis, Penrose and their colleagues measured it. They tracked three passive mirror-covered spheres — LARES, launched in 2012, and the two LAGEOS satellites flying since 1976 and 1992 — with roughly a hundred million laser range measurements over three and a half years, and compared the slow drift of each orbit plane against the Earth’s gravity field as mapped by the GRACE mission. Using three satellites instead of two lets them cancel the two largest error sources, the Earth’s equatorial bulge and the next flattening term after it. The answer is 0.994, where 1.000 is exactly what Einstein predicts, with a formal error of 0.002 and a deliberately conservative systematic error of five percent. On LARES the drag amounts to about 4.5 metres of orbital drift every year.
Connection
This is the cleanest measurement anyone has of mass in motion twisting the metric itself — the very effect chapter 4 asks an engineered field to imitate when a conditioned electromagnetic beam is said to mimic the frame dragging of a rotating mass. The paper also states chapter 2’s central number in its own introduction: quantum field theory puts the vacuum energy about 10^122 times above the dark-energy density actually observed.
From the source
The Earth’s dragging of inertial frames, normalised to its general-relativity value, is measured as 0.994 with a formal 1-sigma error of 0.002 and a preliminary systematic error of 0.05, in agreement with general relativity.Abstract; Sect. 4, Eq. (1); Sect. 5 Conclusions
A current of mass generates an additional contribution to the gravitational field, called the gravitomagnetic field, which torques a gyroscope in the same way a magnetic field torques a magnetic needle in electrodynamics.Sect. 2, Dragging of inertial frames
The Lense–Thirring nodal shift predicted by general relativity is about 30.7 milliarcseconds per year on LAGEOS, about 31.5 on LAGEOS 2 and about 118.4 on LARES, the last corresponding at the LARES altitude to about 4.5 metres per year.Sect. 4, paragraph following Fig. 2
Coupling the nodal rates of three satellites gives three observables for three unknowns, which removes the uncertainties in the two lowest even zonal harmonics of the Earth’s gravity field and leaves a systematic uncertainty of a few percent.Sect. 4, opening paragraph; Sect. 2, closing paragraph
The cosmological constant corresponds to vacuum energy, and quantum field theory predicts that the vacuum energy should have a value approximately 10 to the power 122 times larger than the dark energy density observed in the universe, whose real nature is unknown.Sect. 1, Introduction
Longer observation of LARES, a suite of solutions using different up-to-date Earth gravity models and different orbital solvers, and better models of the non-gravitational forces will tighten the five percent systematic error toward the one percent level in a forthcoming analysis.Sect. 4, discussion of systematic errors
The way in
https://doi.org/10.1140/epjc/s10052-016-3961-8How to cite it
Ignazio Ciufolini, Antonio Paolozzi, Erricos C. Pavlis, Rolf Koenig, John Ries, Vahe Gurzadyan, Richard Matzner, Roger Penrose, Giampiero Sindoni, Claudio Paris, Harutyun Khachatryan, Sergey Mirzoyan (2016) A test of general relativity using the LARES and LAGEOS satellites and a GRACE Earth gravity model doi:10.1140/epjc/s10052-016-3961-8