Most experts agree that general relativity must be modified for quantum theory to work. Scientist Jonathan Oppenheim bet 5000:1 that gravity was not a quantum force because he was not so sure.
While JONATHAN OPPENHEIM likes to bet from time to time, his interests are a little more esoteric than horse racing or one-armed bandits. A quantum physicist at University College London, Oppenheim likes to bet on the fundamental nature of reality, and his latest bet involves spacetime itself.
The two great theories of physics are fundamentally at odds with each other. General relativity, which argues that gravity is the result of mass bending space-time, is depicted in a corner as a kind of flexible sheet. The other is quantum theory, which believes that all matter and energy exist in discrete, small pieces and describes the world at the subatomic level. When put together, they can be used to describe many realities. The only problem is that you can't combine them because the space-time description and the particulate mathematics of quantum theory don't work well together.
The majority of physicists believe that "quantizing" gravity—or showing how space-time, like the other three forces of nature, is made up of tiny quanta—will provide the answer. In practice, this requires modifying general relativity to meet the quantum paradigm, a problem that has plagued scientists for almost a century. Oppenheim, however, questions whether this assumption is wrong and bets 5000:1 that space-time is ultimately not quantum.
In an interview with New Scientist, Oppenheim learns why he believes accepted wisdom in this situation might be wrong, how experiments might answer that question, and why physicists like a good bet.
Jeremy Howgego Is it fair to say that the majority of physicists believe that the best way to combine general relativity with quantum theory is to manipulate quantum theory?
According to Jonathan Oppenheim, general relativity will eventually evolve into a quantum theory. However, there is a difference between those who focus on the quantification of everything and those who study quantum theory. For example, because the relativity group puts a lot of thought into time, there is more uncertainty. You get very confused when you try to quantify time. This raises some concerns.
From my point of view, I honestly don't know! In some ways, a theory that can describe space, time, and the subatomic world, I think, may not be anything like quantum or classical physics. So the question is, will our next theory of gravity look more like a modified classical theory or a quantum theory? I believe we should be more careful. We may be putting all our eggs in one basket, which would be a big mistake.
Why is time particularly an issue?
We see quantum theory as an explanation of subatomic events that develop over time. According to the theory, time acts as a background structure that is always present and affects how quantum systems behave. The problem is that spacetime itself becomes dynamic in general relativity and can bend. If we quantize the time flow rate, we lose the basic background structure on which quantum theory is based. Even discussing a moment in time is difficult, as I can't even say with certainty which "fragments" of space-time are in the future and which are in the past.
Although extremely difficult, it may be possible to extract this background structure from quantum theory. People lack real time management skills.
How did the necessity to quantify gravity come to be accepted as gospel?
When there was a great debate in the 1980s about whether gravity should be quantized or not, I believe it really crystallized. At the time, people decided that it was inconsistent to maintain a classical theory of gravity. However, this can go back even further. There was already a lot of discussion about this in the late 1950s. I have read the minutes of the Chapel Hill conference, an important meeting that took place in 1957 and for which we have a complete historical record.
The subject has been covered in discussions attended by prominent physicists, including Richard Feynman and John Wheeler. It is quite interesting to read. I feel like many of the academics at the conference decided that gravity should be made quantum, mostly based on Feynman's reasoning.
But if you go back and review the arguments, you will see that our knowledge of quantum theory has changed. We now better understand the role of entanglement, the phenomenon of two spatially separated particles appearing to share information, and the similarities between classical probability distributions and quantum wave functions that provide probabilities for the properties of a quantum object to be measured. We now understand that not quantizing gravity can be consistent. However, a certain perspective is already included.
There are many important questions in physics. How important is this example of quantum gravity?
It's an important issue. Any inquiries into cosmology, the standard model of particle physics, or dark matter are inquiries into our particular universe. Although there are many different types of particles and forces in our universe, quantum theories regulate them all. Therefore, the framework we use to understand our reality should be accepted as quantum theory. The question of whether the laws of physics are purely quantum, partly quantum, or something else is therefore of a different kind. It is concerned with the structure of the laws of nature. Almost metaphysical.
Günceleme: 21/03/2023 21:17