by Scientists have determined a way to measure gravity at microscopic levels, possibly bringing them closer to formulating a theory of “quantum gravity” and solving some great cosmic mysteries.
Quantum physics offers scientists the best description of the universe at scales smaller than atoms. Albert EinsteinThe theory of general relativity, on the other hand, provides the best description of physics on massive cosmic scales. However, something is frustratingly missing even after 100 years of both theories passing a wealth of experimental verification.
As strong and accurate as the two theories developed at the beginning of the 20th century became, they have refused to agree.
One of the main reasons for this dilemma is that, although three of the four fundamental forces of the universe have a quantum description — electromagnetism, the strong nuclear force and the weak nuclear force — the fourth has no quantum theory: Gravity.
Now, however, an international team has made progress in tackling this imbalance by successfully detecting the weak gravitational pull of tiny particles using a new technique. The researchers believe that this could be the first tentative step on a path leading to a theory of “quantum center of gravity.”
“For a century, scientists have tried and failed to understand how gravity and quantum mechanics work together,” Tim Fuchs, a team member and scientist at the University of Southampton, said in a statement. “By understanding quantum gravity, we could solve some of the mysteries of our universe – how it started, what happens inside black holes, or unify all forces in one grand theory.”
Related: ‘Wave-stopping space-time’ may explain why gravity won’t play by quantum rules
Gravity gets the ‘spooky’ treatment
Perhaps it is fitting that general relativity and quantum physics will not succeed; after all, Einstein was not comfortable with quantum physics. This is because although there are many counter-intuitive aspects of quantum physics, he found one in particular very upsetting.
It was the notion of entanglement. At the risk of oversimplification, the entanglement must coordinate particles in such a way that changing the properties of one particle immediately changes the properties of the entangled partner particles, even if the partner is located on the other side of the universe. Einstein called the concept of local realism a “frightening act at a distance” as he challenged it.
Local realism is the idea that objects always have defined properties and that interactions between those objects are limited by distance and the speed of light, a universal speed limit introduced by Einstein as the basis of special relativity. Special relativity is, in fact, the theory that led to the formulation of general relativity in the first place. But, despite Einstein’s protests, scientists have indeed proven that entanglement and other counterintuitive aspects of quantum physics are factors of reality on sub-atomic scales.
Such proof has been achieved with many pioneering experiments. Fuchs and colleagues, for example, are following in the footsteps of physicists such as Alain Aspect, John Clauser and Anton Zeilinger, who won the 2022 Nobel Prize in Physics for experimentally verifying the non-local nature of entanglements.
In their new quantum experiment, the researchers, including scientists from the University of Southampton, Leiden University and the Institute of Photonics and Nanotechnologies, used superconducting magnetic “traps” to create the weakest gravitational pull on the smallest mass ever made. try to investigate in this way ever. .
The tiny particle was frozen in the superconducting trap at a temperature of around -459.4 degrees Fahrenheit (-273 degrees Celsius), which is only a few hundredths of a degree above absolute zero, the hypothetical temperature at which all atomic motion would stop. This frigid temperature was required to limit the vibration of the particles to a minimum. Ultimately the team measured a gravitational pull of 30 “attoNewtons” on the particle.
AttoNewtons is a measure of force; to give you an idea of how small the gravitational force of the particles studied was, one Newton is defined as the force required to provide a mass of one kilogram with an acceleration of one meter per second per second. And 30 attoNewtons is equal to 0.0000000000000003 Newtons!
“Now that we’ve successfully measured gravitational signals at the lowest mass ever recorded, it means we’re one step closer to finally figuring out how it all works together,” Fuchs said. “From here, we will start to scale the source down using this technique until we reach the quantum world on both sides.”
RELATED STORIES:
— Albert Einstein: Biography, theories and quotes
— 10 incomprehensible things you should know about quantum physics
— Einstein’s theory of general relativity
Hendrik Ulbricht, team member and University of Southampton scientist, said this experiment paves the way for tests with even smaller masses, as well as measuring even smaller gravitational forces.
“We are pushing the boundaries of science which could lead to new discoveries about gravity and the quantum world. Our new technique using very cold temperatures and devices to isolate the vibrations of particles is likely to prove the way forward to measure quantum gravity,” he concluded. “If these mysteries are solved, this will help us unlock more secrets about the fabric of the universe, from the smallest particles to the largest cosmic structures.”
The team’s research was published Friday (February 23) in the journal Science Advances.
