More than a century ago, two theories were proposed to explain all of reality: quantum mechanics and general relativity. Both have been refined, improved, and extensively tested over decades. Those are solid theories. But in the end, they don’t seem to be able to explain everything on their own, and they don’t seem to work well together. For decades, physicists have focused on the grand unified theory, and his two main candidates have been proposed: string theory and quantum loop gravity. Now, a group of researchers has made a new proposal.
After five years of testing and resolution, this new idea is now available. They call it a “post-quantum theory of classical gravity.” Admittedly the name isn’t as catchy as his other two contenders, but there’s also another big difference. Spacetime in this new theory is not quantized.
To bridge the gap between relativity and quantum mechanics, it has been assumed that spacetime ultimately consists of discrete steps, discrete but much smaller than what can be measured. . In this theory, it is quantum mechanics that changes, and this classical spacetime leads to a breakdown in predictability when a sufficiently high precision is reached.
“Since quantum theory and Einstein’s general theory of relativity are mathematically inconsistent with each other, it is important to understand how this contradiction is resolved. Should we quantize spacetime, or should quantum theory Should we modify it, or is it something else entirely? No one can deduce a consistent fundamental theory that spacetime is not quantized,” said Professor Jonathan Oppenheim of University College London. statement.
It is believed that there are energy fluctuations in space-time, and particles and antiparticles are generated for a moment and then disappear. In the post-quantum theory of classical gravity, these fluctuations are even more intense compared to the quantized spacetime image. The good news is that variation leads to ways to test theories.
In the second paper published in nature communications, the team highlighted how to test the theory. By measuring the mass and weight of objects with high precision, we should be able to determine whether spacetime is classical. Fluctuations can change the measured weight over time, and if those small changes are not seen, a post-quantum theory of classical gravity may be ruled out.
“We showed that if spacetime does not have quantum properties, then there should be random fluctuations in the curvature of spacetime with certain features that can be tested experimentally,” said co-author Zak.・Weller Davis explained.
“In both quantum and classical gravity, space-time must be experiencing violent random fluctuations around us, the magnitude of which we have not yet detected. But if space-time is classical , the fluctuation must be larger than a second.” This scale can be determined by another experiment that tests how long heavy atoms can be left superimposed in two different locations. . ”
Testing this is not something you can do tomorrow, but it is likewise not something you can test in a few lifetimes. Some researchers estimate that the experiment could be done within 20 years.That’s good, because there’s a stake in between. Professor Oppenheim, Professor Carlo Rovelli, Dr. Jeff Pennington, the latter two are proponents of quantum loop gravity theory and string theory, respectively. They are betting 5,000 to 1 that spacetime will be quantized.
The main papers introducing this theory are: Physical Review X.