Friday, August 31, 2018

Strength of Gravity Measured With New Precision

Increased precision in measuring fundamental physical constants pervasively impacts the accuracy of physics measurements and our capacity to distinguish new physics from existing physics, in general. The new data roughly triple the precision with which Newton's constant, a.k.a. G, has been measured to roughly one part per 86,000.
Two new measurements for the strength of gravity (red squares, with short error bars indicating uncertainty) fall close to or within the currently accepted range for Big G (shaded gray). The new estimates are much more precise than those from other experiments in the last 40 years (teal dots and longer error bars).

The current accepted value for G, based on measurements from the last 40 years, is 6.67408 × 10−11meters cubed per kilogram per square second. That figure is saddled with an uncertainty of 0.0047 percent, making it thousands of times more imprecise than other fundamental constants — unchanging, universal values such as the charge of an electron or the speed of light (SN: 11/12/16, p. 24). The cloud of uncertainty surrounding G limits how well researchers can determine the masses of celestial objects and the values of other constants that are based on G (SN: 4/23/11, p. 28). . . . 
These torsion pendulum experiments yielded G values of 6.674184 × 10−11 and 6.674484 × 10−11 meters cubed per kilogram per square second, both with an uncertainty of about 0.00116 percent.
From Science News. The papers it relied upon were:

Q. Li et al. Measurements of the gravitational constant using two independent methods. Nature. Vol. 560, August 30, 2018, p. 582. doi: 10.1038/s41586-018-0431-5.

S. Schlamminger. Gravity measured with record precision. Nature. Vol. 560, August 30, 2018, p. 562. doi: 10.1038/d41586-018-06028-6.

Of course, other physical constant and coupling constant measurements also continue to become more precise.

No comments: