Theoretical physicists have shown that, without resorting to string theory, it is possible explain gravity using quantum mechanics and not contradict the laws of physics.
For decades, most physicists have agreed that string theory is the missing link between Einstein’s theory of general relativity, which describes the laws of nature on the largest scale, and quantum mechanics, which describes them on the smallest scale.
But nevertheless, an international collaboration led by physicists from Radboud University has now provided convincing evidence that string theory is not the only theory that could form the link. They showed that it is possible to build a theory of quantum gravity that obeys all the fundamental laws of physics, without strings. They described their findings in Physical Review Letters.
When we observe gravity at work in our universe, like the motion of planets or light passing near a black hole, everything seems to follow the laws written by Einstein in his theory of general relativity. On the other hand, quantum mechanics is a theory that describes the physical properties of nature in the smallest scale of atoms and subatomic particles.
Although these two theories have allowed us to explain all the fundamental physical phenomena observed, they also contradict each other. To this day, physicists have serious difficulty reconciling the two theories to explain gravity on both the largest and smallest scales.
In the 1970s, physicists proposed a new set of physical principles to address this problem, expanding on the laws proposed by the general theory of relativity. According to this so-called “string theory”, everything that surrounds us is not formed by point particles, but by strings: one-dimensional objects that vibrate. Since its introduction, string theory has been the most widespread theoretical framework believed to complete Einstein’s theory of general relativity to a theory of quantum gravity.
However, a new demonstration by theoretical physicists from Radboud University now shows that string theory is not the only way to do it. “We show that it is still possible to explain gravity using quantum mechanics without using the laws of string theory at all.”says theoretical physicist Frank Saueressig. “We showed that the idea that everything consists of point particles could fit with quantum gravity, excluding strings. This framework of particle physics is also experimentally verified, for example, at the Large Hadron Collider (LHC) at CERN.” .
“For scientists, this alternative theory is attractive to use because it has been extremely difficult to connect string theory with experiments. Our idea uses physical principles that have already been tested experimentally. In other words, no one observed strings in experiments, but particles are things that people definitely see in the LHC experiments. This allows us to bridge the gap between theoretical predictions and experiments more easily. “.
Having shown that his ideas are capable of solving long-standing problems in particle physics, the consortium is currently exploring the implications resulting from its new laws at the level of black holes.
After all, there is only one set of laws of nature and this set should be applicable to all kinds of questions, including what happens when we collide particles at incredibly high energies or what happens when particles fall into a black hole. It would be great to show that there is actually a link between these seemingly disconnected questions that solves the puzzles that appear on both sides. ”