In the 1970s, physicists Stephen Hawking and Jacob Bekenstein noticed a connection between the surface area of black holes and the microscopic quantum structures that determine their entropy. This was recorded as the first link established between Einstein's general relativity and quantum mechanics.
Nearly 30 years later, theoretical physicist Juan Maldacena observed another connection between gravity and the quantum world. This connection led to the development of a model that suggests that space-time can be created or destroyed by varying the amount of entanglement between different surface regions of an object. In other words, this model proposes that space-time is a product of entanglement between objects.
To delve deeper into this idea, ChunJun Cao and Sean Carroll of the California Institute of Technology (Caltech) set out to see if they could derive the dynamic properties of gravity (which we are familiar with from general relativity) using the structure in which space-time consists of quantum entanglement. They published their work on the online platform arXiv.
With the help of an abstract mathematical concept called Hilbert space, Cao and Carroll were able to find similarities between the equations governing quantum entanglement and Einstein's equations of general relativity. This supports the idea that space-time and gravity arose from entanglement.
Today, nearly everything we know about the physical properties of our universe can be explained by either general relativity or quantum mechanics. General relativity does a good job of explaining movements at the very large scale, such as galaxies and planets, while quantum mechanics helps us understand the world at the very small scale, such as atoms and subatomic particles. However, these two theories do not seem very compatible with each other. This has led physicists to seek a "theory of everything," an elusive theory that explains everything, including the nature of space and time.
Since gravity and space-time are such important parts of "everything," their work could advance the search for a theory that reconciles general relativity with quantum mechanics, according to Carroll. However, he also points out that his work is open to discussion and narrow in scope. “Our work doesn't say much about other forces of nature, at least for now. That's why we're still a long way from integrating 'everything',” adds Carroll.
Still, if we can find such a theory, we may find answers to some of the biggest problems scientists face today. For example, we can understand the true nature of dark matter, dark energy, black holes, and other mysterious cosmic objects.
Researchers are already taking advantage of the quantum world to develop computing technologies, and a theory of everything can accelerate this process by bringing new perspectives to issues that continue to confuse people.
While the process of theoretical physicists' search for a theory of everything is still somewhat "ragged", each new piece of research, debatable or not, brings us one step closer to that theory and to leading a new era in humanity's understanding of the universe.
Two researchers have discovered a potential bridge between general relativity, one of the leading theories in physics, and quantum mechanics, which could require physicists to rethink the nature of space and time.
Albert Einstein's general theory of relativity defines gravity as a geometric property of space and time. The greater the mass of an object, the greater the bending of space-time, and this bending is felt as gravity.