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An impressive achievement by the Austrians. They measured the gravitational influence of an object with the mass of a bee

Gravity is one of those forces whose influence we constantly feel. At the same time, it is one of the least understood physical phenomena. This weakest of all fundamental interactions is one of the reasons why we use the general theory of relativity not with the quantum mechanics can unify. Understanding it in detail is one of the most important challenges in physics today. So it is extremely important to be able to test gravity on all possible scales.
 

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So far, such experiments have been carried out on macroscopic scales, with objects whose mass is counted in kilograms. Researchers at the Institute for Optics and Quantum Information of the Austrian Academy of Sciences and the Faculty of Physics at the University of Vienna have in Nature on proof of a gravitational Interaction reported between two golden spheres with a diameter of 2 millimeters each. The Mass each ball was less than 100 milligrams.

The authors of the experiment used a fairly standardized device. In fact, they repeated that Cavendish experiment. They used a torsion balance built from a 4 cm long glass rod with a diameter of 0,5 mm. The golden balls mentioned above were attached to both ends of the staff. The rod was suspended in the middle on a thin glass fiber so that it could rotate freely. A mirror was attached to the bracket to allow the laser light to reflect. Of the Center of mass was a gold ball with a diameter of 2 millimeters and a weight of 90 micrograms. Balls attached to the rod were brought near this ball in the hopes that the ball would attract them, causing the mirror to rotate. This in turn would change where the laser light goes when it is reflected. This architecture enabled extremely precise measurements.

The problem, however, is the external interference that needs to be eliminated somehow. And that's not easy. Suffice it to say, people and trams moving around the lab are the source of serious ones seismic disturbances were. To minimize this, the experiments were carried out at night during the Christmas holidays. The tester was placed on a rubber base in a vacuum chamber which was first filled with ionized nitrogen to remove any electrical charge. As a precaution, a Faraday cage was placed between the balls to prevent them from getting through electrostatic interactions attract.

While trying to keep any interference as low as possible, the scientists knew that the interaction between such spheres of light would also be small. So instead of measuring how much they attract each other, the scientists moved the spheres in a regular pattern, with the frequency of the movements chosen so that they were completely different from the natural response differs. This resulted in a time-changeable one Gravitational field and weight vibrations, explains Jeremias Pfaff.