We still don't have a more precise value for "Big G"

Despite decades of attempts, the gravitational constant remains stubbornly imprecise, leaving a fundamental gap in physics. | Contesto: cronaca

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• We still don't have a more precise value for "Big G"

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The gravitational constant, known as Big G, remains as elusive as ever. Despite numerous experiments over the past century, scientists have yet to pin down a more precise value for this fundamental constant, which governs the force of gravity. The latest attempts, detailed in recent studies, have failed to narrow the uncertainty, leaving physicists with a number that is still only known to about four significant digits—far less precise than other constants like the speed of light or Planck's constant. Big G is a cornerstone of Newton's law of universal gravitation and Einstein's theory of general relativity. It determines the strength of the gravitational attraction between two masses. Yet, it is notoriously difficult to measure because gravity is incredibly weak compared to other fundamental forces, and experiments are easily disturbed by tiny vibrations, temperature changes, or magnetic fields. The current accepted value, about 6.67430 × 10^-11 cubic meters per kilogram per second squared, carries a relatively large uncertainty of around 22 parts per million. The recent experiments, conducted at laboratories in Europe and the United States, used variations on classic torsion balances and pendulum techniques. Researchers suspended masses and measured their tiny twists or swings with laser interferometers and other sensitive instruments. While each experiment achieved impressive precision individually, their results did not converge to a common value. Instead, they differed by more than their stated uncertainties, suggesting that systematic errors—hidden flaws in the experimental setup—are still confounding the measurements. This persistent discrepancy has significant implications. Without a more precise Big G, calculations of planetary orbits, the mass of the Earth, and the dynamics of galaxies carry extra uncertainty. In cosmology, it affects models of the universe's expansion and the behavior of dark energy. Moreover, any future theory that unifies gravity with quantum mechanics will require a more accurate value to test its predictions. As one physicist involved in the work noted, such experiments bring "order to the universe, whether or not the number...

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Categoria: cronaca