## Scientists Admit, Embarrassingly, We Don’t Know How Strong The Force Of Gravity Is

“The gravitational constant of the Universe, G, was the first constant to ever be measured. Yet more than 350 years after we first determined its value, it is truly embarrassing how poorly known, compared to all the other constants, our knowledge of this one is. We use this constant in a whole slew of measurements and calculations, from gravitational waves to pulsar timing to the expansion of the Universe. Yet our ability to determine it is rooted in small-scale measurements made right here on Earth. The tiniest sources of uncertainty, from the density of materials to seismic vibrations across the globe, can weave their way into our attempts to determine it. Until we can do better, there will be an inherent, uncomfortably large uncertainty anywhere the gravitational phenomenon is important. It’s 2018, and we still don’t know how strong gravity actually is.”

Of all the fundamental constants in the Universe, such as Planck’s constant, the speed of light, or the mass of the electron, only one of them can lay claim to being the first one to be identified and measured to any degree of accuracy. That is G, the gravitational constant, first determined decades before Newton’s work: in the mid-17th century. Yet even today, scientists performing the experiments can’t agree on whether it’s 6.672 or 6.676 (or somewhere in between) x 10^-11 N/kg^2/m^2. Experiments are coming out all the time, claiming precisions to just a few parts-per-million, yet they disagree with one another at the level of nearly a part in a thousand, making G the least well-determined fundamental constant of all.