Apr 29, 2021 18:00:00

How did it prove that even an object weighing only 90 milligrams is attracted by gravity?

In physics, there are four

basic interactions : strong interaction , weak interaction , electromagnetic force, and gravity . Gravity is the weakest of these four, and it is very difficult to measure the universal gravitational force acting between objects under the influence of the earth's gravity. Meanwhile, the Institute for Quantum Optics and Quantum Information (IQOQI) in Austria reports that it has experimentally detected a very small amount of gravity acting between objects weighing only 90 milligrams.

[2009.09546] Measurement of Gravitational Coupling between Millimeter-Sized Masses
https://arxiv.org/abs/2009.09546

Ultra-weak gravitational field detected
https://www.nature.com/articles/d41586-021-00591-1

The mechanism of gravity can be explained by the general theory of relativity published by Albert Einstein, but in the general range, Isaac Newton advocated in the 17th century, 'Between two objects, the mass of the object It can be explained by the theory that 'a universal gravitational force that is proportional and inversely proportional to the square of the distance between objects is acting.'

However, when it comes to the galaxy scale, it is gradually becoming clear that the laws of mechanics advocated by Newton do not apply.

For example, according to the law of universal gravitational force that 'the strength of attraction of objects is inversely proportional to the square of the distance between objects', if two objects are far apart, the influence of gravity is almost eliminated, so it is outside the galaxy. A star should be out of rotation and blown away. However, the innumerable celestial bodies that make up the galaxy rotate almost stably regardless of the distance from the center of the galaxy, which is a contradiction.

In order to correct this 'difference between theory and observation results', '

modified Newtonian dynamics ' was proposed, which is a review of Newtonian dynamics. In addition, there is a need to modify the gravitational constant involved in the calculation of universal gravitation. However, gravity is ^{an extremely weak force of 1/10 36} of the electromagnetic force, and it is extremely difficult to measure minute gravity on the earth, which is affected by the gravity of the earth and the sun. At the time of writing the article, the gravitational constant is less accurate than other constants, and the values recommended by the Committee on Data for Science and Technology are being used. Therefore, physicists around the world are trying to experimentally measure the gravitational constant.

Meanwhile, a research team of IQOQI researchers Tobias Westfal and others conducted an experiment to measure a very weak gravitational field.

The following device, created by the research team, has two test gold balls attached to both ends of a uniform rod, and is hung by a silicon cable attached to the center of gravity. The research team brought a separately prepared gold ball close to one of the test gold balls while sandwiching a Faraday shield that blocks the electromagnetic field, and moved it regularly within a range of about 3 mm.

In addition, a mirror is attached to the center of the balance to irradiate the laser. When the sensor receives the reflected laser, it can detect the slight movement of the balance. When the research team moves the gold ball closer to or further away from it, and a change occurs in the weak gravitational field, the device and mirror move and the reflected laser beam is displaced.

The gold balls used in the experiment weigh only 92 milligrams. When the distance between the centers of gravity is 2.5 mm, the gravity acting between the two gold balls is almost the same as the force applied to about one-third the mass (9 trillion grams) of human red blood cells in the gravitational field of the earth. It will be the same strength. The photo below shows the actual gold ball placed on a 1-cent bronze coin and the actual experimental equipment.

When the research team actually moved the gold ball, the displacement of the laser beam was observed. In addition, when the universal gravitational constant was actually calculated from the displacement of the laser beam, it deviated by about 9% from the value recommended by the Committee on Data for Science and Technology. According to the research team, this 9% error is a slight difference, considering the uncertainty due to the vibration damping of the balance.

At the very least, Westfal's experiments are the first to show that even objects of very small mass are attracted to each other by gravity. The scientific journal Nature said, 'The challenge is to reduce the vibration damping of the balance as much as possible, but this is not an easy task. If it can be achieved, we may finally be able to demonstrate quantum gravity theory .' Said.