A step towards quantum gravity

In Einstein's theory of general relativity, gravity arises when a massive object distorts the fabric of spacetime the way a ball sinks into a piece of stretched cloth.

Solving Einstein's equations by using quantities that apply across all space and time coordinates could enable physicists to eventually find their 'white whale': a quantum theory of gravity.

In a new article in EPJ Historical Perspectives on Contemporary Physics, Donald Salisbury from Austin College in Sherman, USA, explains how Peter Bergmann and Arthur Komar first proposed a way to get one step closer to this goal by using Hamilton-Jacobi techniques.

Three of the four fundamental forces - strong, weak, and electromagnetic - hold under both the ordinary world of our everyday experience, modelled by classical physics, and the spooky world of quantum physics.

Problems arise when trying to apply to the fourth force, gravity, to the quantum world.

In the 1960s and 1970s, Peter Bergmann of Syracuse University, New York and his associates recognised that in order to someday reconcile Einstein's theory of general relativity with the quantum world, they needed to find quantities for determining events in space and time that applied across all frames of reference.

Salisbury concludes that because the approach taken by Bergmann and associates resolves the ambiguity in the way time develops, their approach deserves more recognition by those exploring an eventual theory of quantum gravity.

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There are four fundamental forces that describe every interaction in nature: electromagnetism, the weak force, the strong force and gravity.

Insights into gravity could lead to greater understanding of phenomena as abstract as the beginnings of the universe and as concrete as high-temperature superconductors.