According to general relativity, photons are deflected and delayed by the curvature of space-time produced by any mass. The bending and delay are proportional to γ + 1, where the parameter γ is unity in general relativity but zero in the newtonian model of gravity. The quantity γ - 1 measures the degree to which gravity is not a purely geometric effect and is affected by other fields; such fields may have strongly influenced the early Universe, but would have now weakened so as to produce tiny-but still detectable-effects. Several experiments have confirmed to an accuracy of ∼0.1% the predictions for the deflection and delay of photons produced by the Sun. Here we report a measurement of the frequency shift of radio photons to and from the Cassini spacecraft as they passed near the Sun. Our result, γ = 1 + (2.1 ± 2.3) × 10-5, agrees with the predictions of standard general relativity with a sensitivity that approaches the level at which, theoretically, deviations are expected in some cosmological models.
Bertotti B., Iess L., Tortora P. (2003). A test of general relativity using radio links with the Cassini spacecraft. NATURE, 425(6956), 374-376 [10.1038/nature01997].
A test of general relativity using radio links with the Cassini spacecraft
Tortora P.
2003
Abstract
According to general relativity, photons are deflected and delayed by the curvature of space-time produced by any mass. The bending and delay are proportional to γ + 1, where the parameter γ is unity in general relativity but zero in the newtonian model of gravity. The quantity γ - 1 measures the degree to which gravity is not a purely geometric effect and is affected by other fields; such fields may have strongly influenced the early Universe, but would have now weakened so as to produce tiny-but still detectable-effects. Several experiments have confirmed to an accuracy of ∼0.1% the predictions for the deflection and delay of photons produced by the Sun. Here we report a measurement of the frequency shift of radio photons to and from the Cassini spacecraft as they passed near the Sun. Our result, γ = 1 + (2.1 ± 2.3) × 10-5, agrees with the predictions of standard general relativity with a sensitivity that approaches the level at which, theoretically, deviations are expected in some cosmological models.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.