The Economist says that "physicists have worked out how to look at the smallest sizes and shortest time that some of them believe can exist."
It starts by comparing the quantum theory, which states that space and time are grainy, to the theory of relativity, which assumes that space is continuous.
It is the dream of many theorists of fundamental physics to reconcile quantum theory with relativity, and thus produce a grainy theory of quantum gravity. Doing so means knowing what is going on at the Planck scale. And that is hard, because, in physics, probing smaller and smaller things requires bigger and bigger energies.
The energy that would be needed to probe the granularity of space is known as the Planck energy. Unfortunately, even the biggest particle accelerators in existence probe energies which are only about a millionth of that. The lack of a reality check which this causes has led theorists so far into the deep end of mathematical speculation that many have started to question if what they are doing is still physics.
In the past ten years, this has begun to change. Physicists have realised that, if brute force is not going to work, they will have to be clever.
The well-documented article then looks at several current research projects.
In the March 10th issue of Astrophysical Journal Letters, Richard Lieu and Lloyd Hillman of the University of Alabama, in Huntsville, will describe a new method they have used to look at Planck time. Dr Lieu supposed that light, travelling over very long distances, would have to spread out a bit if there was any uncertainty in time. This effect would normally be too small to measure, but Dr Lieu realised that “phase coherence” -- a precise synchronisation of the waves that make up a beam of light -- is necessary in order for rings, known as diffraction rings, to show up in a telescope. He then examined a picture taken by the Hubble space telescope of a galaxy several billion light-years away. This galaxy has the characteristic ring. So, says Dr Lieu, time (and therefore space) is continuous, not grainy.
However, not everyone agrees with Dr Lieu. Jack Ng and his colleagues at the University of North Carolina, Chapel Hill, have written a paper arguing that Dr Lieu overestimated by a factor of several million the effect that fluctuations in space and time would have on light.
If you want to know more about Lieu and Hillman's project, please read the abstract of their paper, "The Phase Coherence of Light from Extragalactic Sources."
I'll leave the last word to Albert Einstein himself.
Commenting on the uncertainty principle, and by inference on its malevolent effects for relativity, Einstein once famously said "God does not play dice." Soon, it should be possible to see if he was right.
Sources: The Economist print edition, February 27, 2003; Richard Lieu and Lloyd W. Hillman, The Astrophysical Journal Letters, March 10, 2003, Volume 585, Number 2, Part 2
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