Researchers remeasure gravitational constant


The gravitational constant G has been recalculated by ETH Zurich researchers using a novel measurement method. Even though there is still a lot of uncertainty surrounding this number, the new approach has a lot of promise for evaluating one of nature's most fundamental rules.

The gravitational force Gravitational force, which causes objects like apples to fall to the ground or pulls the Earth in its orbit around the sun, is quantified by the constant G. It is a component of Isaac Newton's law of universal gravitation, which was created almost 300 years ago. The constant must be discovered by experimentation because it cannot be mathematically derived.

The value of G has been the subject of several tests throughout the years, but the scientific community is unsatisfied with the result. It nevertheless lacks the accuracy of all the other fundamental natural constants, such as the vacuum-induced speed of light.

Gravity is a very weak force that cannot be isolated, which makes it incredibly challenging to measure. When you measure the gravity between two bodies, you also estimate the impact of all other bodies in the universe.

Jürg Dual, a professor in the Department of Mechanical and Process Engineering at ETH Zurich, says that the only way to deal with this issue is to quantify the gravitational constant using a variety of techniques. In order to recalculate the gravitational constant, he and his colleagues carried out a new experiment. They have recently published their findings in the academic journal Nature Physics.

An innovative test in a former fortification

Dual's team put up their measuring equipment at the former Furggels stronghold, which is located close to Pfäfers above Bad Ragaz, Switzerland, in order to exclude sources of interference as much as possible. Two beams hung in vacuum chambers make up the experimental setup. Gravitational coupling made the second beam barely move after the scientists made the first vibrate (in the picometre range — i.e., one trillionth of a metre). The researchers used laser equipment to detect the speed of the two beams, and by measuring this dynamic effect, they were able to estimate the gravitational constant's size.

The value that the researchers determined using this method is 2.2 percent greater than the one that the Committee on Data for Science and Technology now declares to be the official value. Dual agrees that there is a lot of ambiguity surrounding the new number, though: "We still need to significantly minimize this uncertainty in order to have a reliable value. In order to calculate the constant G with even more accuracy, we are currently performing measurements with a slightly altered experimental setup." Although they have not yet been published, the preliminary results are available. Dual said, "We're on the right road," despite this.

In order to minimize interference from on-site workers, the experiment is run remotely from Zurich by the researchers. The team can pick whenever to access the measurement data in real time.

Understanding of the universe's past

For Dual, the benefit of the new technique is that it uses the moving beams to dynamically measure gravity. He claims that the fact that it is impossible to isolate the gravitational effect of other bodies in dynamic measurements is irrelevant. He therefore thinks that he and his team might use the experiment to aid in solving the mystery behind gravity. The tests that relate to this natural force and its effects are still not fully understood by science.

For instance, a deeper comprehension of gravity would improve our ability to decipher gravitational wave transmissions. At the US LIGO observatories, such waves were first discovered in 2015. They were the outcome of the merger of two black holes in orbit that were 1.3 billion light years away from Earth. Since then, scores of such occurrences have been recorded by scientists; if they could be precisely tracked down, they would offer fresh perspectives on the origins of the universe.

A highlight of your career

In 1991, Dual started developing techniques for calculating the gravitational constant, but he once took a break from his studies. However, it gained new pace once gravitational waves were discovered at LIGO, and he picked up his research again in 2018. The project team established the lab in the stronghold of Furggels in 2019 and started conducting fresh research. The project included members of the infrastructure such as cleanroom specialists, an electrical engineer, and a mechanic in addition to the scientists from Dual's group and a professor of statistics. Without years of teamwork, this project "couldn't have come together," claims Dual. He will retire as a professor at the end of this year's July. The scientist says, "A successful experiment is a good way to close my career.

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