Physicists have measured the smallest gravitational field ever recorded in an experiment that could aid in the search for a unified theory of physics.
Of the four fundamental forces known to physics – the weak and strong interactions, the electromagnetic force, and gravity – only gravity remains unintegrated in the playbook of physics, called the Standard Model, which describes how the zoo of subatomic particles behaves. Gravity is instead described by Einstein’s general theory of relativity, but as this breaks down on the quantum scale, our best picture of the universe remains split in two.
As a result, physics still cannot describe how gravity works at subatomic scales, leaving physicists scratching their heads when it comes to understanding the singularities that lie at the centers of black holes, or why gravity is so much weaker in strength is then all others. the other forces.
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But a new experiment measuring the miniscule gravitational pull between two tiny gold spheres, each just 2 millimeters wide, could be the first of many to provide clues as to how gravity works on this scale.
“This was a proof-of-concept experiment to create a sensor capable of measuring very small accelerations and to develop methods to detect even smaller gravities,” study co-author Jeremias Pfaff, a researcher. doctoral student at the University of Vienna, told Live Science. “In the long run, we want to answer what the gravitational field of a quantum object in superposition looks like, but there’s still a lot to be done,” said Pfaff, referring to the gravitational pull experienced by a subatomic object. particle that is in two quantum states at the same time.
To get an idea of how gravity works on a small scale, the researchers used a small version of a torsion balance – a device first devised by the English scientist Henry Cavendish in 1798 to measure the density of the Soil, and from that the strength of the gravitational constant called G.
A torsion balance is a horizontal bar suspended from the center by a wire with two masses, in this case golden spheres, attached to each end. This means that as a small force applied along the horizontal axis of the bar, the wire will turn and scientists can measure the force applied based on how much the bar has turned. By bringing a third golden sphere close to one of the spheres at the end of the rod, the researchers were able to measure the gravity between the sphere and the sphere attached to it.
The power the researchers were looking for was small. At about 9 × 10 ^ minus 14 newtons, it would be the force that is one third of a human blood cell would experience in the Earth’s gravitational field. So the experiment had to be incredibly sensitive, and the researchers had to minimize exposure to ambient noise, make sure no loose charges build up on the device, and find a way to find the desired signal.
“The urban environment is also far from ideal,” says Pfaff. “It was amazing to see that we are not only sensitive to small earthquakes, but also to the local trams and some buses. We could even see the Vienna City Marathon in our data.”
They removed any stray charges by flooding the area around the device with ionized nitrogen before putting it in a vacuum. They also made the tiny gravitational signal they were looking for more noticeable by moving the two spheres closer and further apart each time.
In much the same way that a flashing light is more noticeable than a steady light, the growing and diminishing gravity between the bulbs was much easier to notice than when they were stationary. This allowed the researchers to find the strength of the gravitational force between the two spheres, as well as their own measurement for the gravitational constant.
So far, gravity on the scale they were measuring followed the same predictable rules as on a larger scale. The physicists now hope to make their experiment even more sensitive so that they can pick up smaller signals from masses that are at least 1,000 times lighter and at shorter distances. This could provide important clues to a theory that explains gravity on both a small and large scale, along with insights into other mysteries such as the existence of dark matter, a mysterious form of matter that does not emit light but still exerts gravity.
On a smaller scale, the researchers could discover completely new ways in which matter interacts through gravity – ways that follow the much more bizarre rules of the quantum world. If they do, physics could finally bridge the gap between our large and small images of the universe.
“By expanding our knowledge of this elusive force, we can gather hints to find a more fundamental understanding of our physical reality,” said Pfaff.
Originally published on Live Science.