Abstract
Light can be used as a probe to explore the structure of space-time: this is usual in astrophysical and cosmological tests; however, it has been recently suggested that this can be done also in terrestrial laboratories. Namely, the Gyroscopes In General Relativity (GINGER) project aims at measuring post-Newtonian effects, such as the gravito-magnetic ones, in an Earth-based laboratory, by means of a ring laser array. Here, we first review the theoretical foundations of the Sagnac effect, on which ring lasers are based, and then, we study the Sagnac effect in a terrestrial laboratory, emphasizing the origin of the gravitational contributions that GINGER aims at measuring. Moreover, we show that accurate measurements allow one to set constraints on theories of gravity different from general relativity. Eventually, we describe the experimental setup of GINGER.
Highlights
2015 is the International Year of Light [1], and it celebrates the importance of light in science, technology and society development
As for physics, it is always useful to remember the central role of light in the genesis of the Theory of Relativity: in his Autobiographical Notes, Einstein wrote that, at the age of 16, he imagined chasing after a beam of light and that this thought experiment had played a very important role in the development of special relativity. 2015 precedes by one year the centennial celebration of the publication of general relativity (GR): it is interesting to emphasize that, except for the perihelion shift, the classical tests of GR exploit light as a probe; think of the gravitational
Since we are interested in the Sagnac effect in a terrestrial laboratory, in Section 3, we focus on the definition of the space-time metric in the frame where the interferometer is at rest, and in Section 4, we study the outcome of a Sagnac experiment, performed on the Earth, starting from a somewhat generic expression of the terrestrial gravitational field, in terms of a suitable post-Newtonian parameterized (PPN) space-time metric
Summary
2015 is the International Year of Light [1], and it celebrates the importance of light in science, technology and society development. On the one hand, GR has been verified with excellent agreement in the Solar System and in binary pulsar systems [3], but on the other hand, its reliability is questioned by observations at large scales, where the problems of dark matter and dark energy are still unsolved To solve these issues and to try to reconcile gravity with quantum theory, several theories have been proposed that are alternative to GR or that extend Einstein’s theory. Since we are interested in the Sagnac effect in a terrestrial laboratory, in Section 3, we focus on the definition of the space-time metric in the frame where the interferometer is at rest, and in Section 4, we study the outcome of a Sagnac experiment, performed on the Earth, starting from a somewhat generic expression of the terrestrial gravitational field, in terms of a suitable post-Newtonian parameterized (PPN) space-time metric.
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