The gravitational constant describes the intrinsic strength of gravity and can be used to calculate the gravitational pull between two objects.
Also known as the “Big G” or Gthe gravitational constant was first defined Isaac Newton In the Law of Universal Gravity, which he formulated in 1680. (6.6743 ± 0.00015) value x10^–11 m^3 kg^–1 s^–2 (opens in new tab).
The gravitational pull between two objects can be calculated with the gravitational constant using an equation many of us faced in high school: The gravitational force between two objects is found by multiplying the masses of those two objects (m1 and m2), and Gand then dividing by the square of the distance between the two objects (F = [G x m1 x m2]/r^2).
Related: Why is gravity so weak? The answer may lie in the nature of spacetime.
Keith Cooper is a freelance science journalist and editor in the UK and holds a degree in physics and astrophysics from the University of Manchester. He is the author of “The Contact Paradox: Challenging Our Assumptions in the Search for Extraterrestrial Intelligence” (Bloomsbury Sigma, 2020) and has written articles on astronomy, space, physics and astrobiology for numerous journals and websites.
gravitational constant
The gravitational constant is the key to measuring the mass of everything in the universe. Universe.
For example, once the gravitational constant is known, it is combined with the acceleration due to gravity. Soil, the mass of our planet can be calculated. When we know the mass of our planet, knowing the size and period of the Earth’s orbit allows us to measure the mass of our planet. Sun. And knowing the mass of the sun allows us to measure the mass of everything in it. Milky Way galaxy the inner part of the sun’s orbit.
Measuring the gravitational constant
measurement G It was one of the first high-precision science experiments, and scientists are investigating whether it could change at different times and places in space, which could have major implications for cosmology.
Reaching 6.67408 x10^–11 m^3 kg^–1 s^–2 for the gravitational constant means that the surveyor Map of the border between the states of Pennsylvania and Maryland (opens in new tab).
British scientist Henry Cavendish (opens in new tab) (1731-1810), interested in calculating the density of the earth carried out (opens in new tab) the expert’s efforts be doomed to fail (opens in new tab) because nearby mountains would distort the surveyors’ readings by subjecting the ‘plumb’ (a tool that provides a vertical reference line from which surveyors can take their measurements) to a slight gravitational pull. if they knew the size Gthey can calculate the gravity of the mountains and change their results.
So Cavendish set about making the measurement, the most precise scientific measurement ever made in history.
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his experiment it was calledtorsion balance technique‘. It contained two dumbbells that could rotate around the same axis. On one of the dumbbells were two small lead spheres, connected by a bar and suspended elegantly by a fiber. The other dumbbell had two large lead weights of 348 pounds (158 kilograms) that could rotate to either side of the smaller dumbbell.
When the larger weights were positioned close to the smaller spheres, the gravitational force of the larger spheres pulled the smaller spheres, causing the fiber to twist. The degree of twist allowed Cavendish to measure the torque (rotational force) of the twisting system. He then used this value instead of ‘ for torque.F‘ in the equation described above, and with the masses and distances of the weights, he could rearrange the equation to calculate. G.
Can the gravitational constant change?
The fact that the “big G” is not known to as many decimal places as other fundamental constants is a source of frustration among physicists. For example, a person’s wage electron known to nine decimal places (1.602176634 x 10^–19 coulombs), but G measured accurately to only five decimal places. Annoyingly, efforts to measure it more precisely you disagree with each other (opens in new tab).
One reason is that the gravity of things around the experimental setup will interfere with the experiment. However, there is also a nasty suspicion that the problem is not just experimental, but that it could be. some new physics at work (opens in new tab). It’s even possible that the gravitational constant isn’t as constant as scientists think.
In the 1960s, physicists Robert Dicke, who participated in his team’s discovery, cosmic microwave background (CMB) in 1964 by Arno Penzias and Robert Wilson) – and Carl Brans, Albert Einstein‘with general theory of relativity. A scalar field describes a property that can potentially change at different points in space (a Earthy analog is a temperature map, where the temperature is not constant, but varies with location). If gravity were a scalar field, then G can have potentially different values in space and time. This differs from the more accepted version of general relativity, which assumes that gravity is constant throughout the universe.
Motohiko Yoshimura of Okayama University in Japan suggested that a scalar-tensor theory of gravity could be linked together. cosmic inflation with dark energy. The inflation occurred fractions of a second after the birth of the universe and led to a brief but rapid expansion of space, which lasted between 10^–36 and 10^–33 seconds after the birth of the universe. Big BangIt inflates the cosmos from microscopic to macroscopic before mysteriously shutting down.
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dark energy It is the mysterious force that is accelerating the expansion of the universe today. Many physicists wondered if there was a connection between the two diffusive forces. Yoshimura proposes that both are manifestations of a gravitational scalar field. much stronger in the early universethen weakened, but strengthened again as the universe expanded and matter spread further.
However, it tries to try and detect any significant variation. G Nothing has been found so far in other parts of the universe. For example, in 2015, the results of a 21-year study on the body’s regular heart rate. pulsar PSR J1713+0747 no evidence found (opens in new tab) For gravity that has a different strength than it does here in the Solar System. Both of them Green Bank Observatory and Arecibo radio telescope It was followed by PSR J1713+0747, located in a binary system 3750 light-years away. white dwarf. The pulsar is one of the most ordered pulsars known, and any deviation from the “Big G” would quickly become apparent during the period of the orbital dance with the white dwarf and the timing of its pulsations.
Inside Declaration (opens in new tab)Weiwei Zhu of the University of British Columbia, who led the PSR J1713+0747 study, said, “The gravitational constant is a fundamental constant of physics, so it’s important to test this basic assumption using objects in different places, times, and gravitational conditions The fact that we see gravity is somewhere far away in our solar system. like doing the same thing. stale The system helps confirm that the gravitational constant is truly universal.”
Additional resources
a review gravity lab tests (opens in new tab) It was conducted by the Eöt-Wash group at the University of Washington.
a review Tries to measure the ‘big G’ (opens in new tab) and what the results might mean.
of Britannica definition of gravitational constant (opens in new tab).
bibliography
“Precise measurement of Newton’s gravitational constant (opens in new tab)”Xue, Chao et al. National Science Review (2020).
“The Bizarre Example of the Gravitational Constant (opens in new tab)” Proceedings of the National Academy of Sciences (2022).
“Henry Cavendish (opens in new tab)”Britannica (2022).
Follow Keith Cooper on Twitter @21stCenturySETI (opens in new tab). Follow us on Twitter @Spacedotcom (opens in new tab) and he Facebook (opens in new tab).
