Charlie Wood
How Our Reality May Be a Sum of All Possible Realities | Quanta Magazine
The Feynman path integral is a powerful formula in physics that predicts the behavior of quantum systems. It suggests that our reality is a sum of all possible possibilities, but it doesn't provide a clear method for carrying out the sum. Physicists have developed approximation schemes to calculate the integral for different quantum systems. The path integral has been successful in predicting outcomes and has been used to understand the behavior of particles and quantum fields. However, mathematicians have concerns about the path integral operating in an infinite environment. Physicists are still working on understanding and harnessing the power of the path integral, particularly in relation to the quantum nature of gravity and space-time.
The most powerful formula in physics starts with a slender S, the symbol for a sort of sum known as an integral. Further along comes a second S, representing a quantity known as action. Together, these twin S’s form the essence of an equation that is arguably the most effective diviner of the future yet devised. The oracular formula is known as the Feynman path integral. As far as physicists can tell, it precisely predicts the behavior of any quantum system — an electron, a light ray or even a black hole. The path integral has racked up so many successes that many physicists believe it to be a direct window into the heart of reality. “It’s how the world really is,” said Renate Loll, a theoretical physicist at Radboud University in the Netherlands. (View Highlight)
“Instead of summing over all paths, you sum over all configurations of your fields.” You identify the field’s initial and final arrangements, then consider every possible history that links them. (View Highlight)
One camp suspects that everything goes in. Stephen Hawking, for instance, championed a path integral that accommodates rips, wormholes, doughnuts and other wild “topological” changes between shapes of space. He leaned on the imaginary-number hack for time to make the math easier. Making time imaginary effectively turns it into another dimension of space. In such a timeless arena there’s no notion of causality for wormhole-ridden or ripped universes to spoil. Hawking used this timeless, “Euclidean” path integral to argue that time began at the Big Bang and to count the space-time building blocks inside a black hole. Recently, researchers used the Euclidean approach to argue that information leaks out of dying black holes. (View Highlight)
But the richer perspective comes at a price. Some physicists dislike removing a load-bearing element of reality such as time. The Euclidean path integral “is really completely unphysical,” Loll said. (View Highlight)
Note: yes that's the point - time is just a mathematical construct not something 'real'