Semi-Daily Journal

Planck Scale Reality

It's sad to think that I will never understand quantum gravity or particle physics in the way I understand special relativity or basic electromagnetism. (Leave to one side the subjects--like angular momentum--where I could do the calculations correctly, but simply could not make myself believe that the results made any sense.) On the other hand, the parts of the universe I do understand are really quite amazing. A gallon jug of a strange liquid can be used to propel that one-ton automobile over a distance of twenty miles (or that SUV over five miles). And could anything be spookier than the rainbow diffraction pattern on the back of a CD, with what it tells us about the manyfold splitting and recombination of our world line (or, alternatively, about the mystical "reduction of the wave packet")?

Economist.com | Planck-scale physics" ...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. They have found a number of places, both in the night sky and in the laboratory, where the nature of space and time at the Planck scale would have indirect, but observable effects. What they have seen so far places tight restrictions on the form that any theory might take. Most theorists seem pleased?they are doing physics again. More cynical experimenters say that the golden age of theory is over, now that the days of freewheeling mathematical carousing are drawing to a close. Richard Lieu and Lloyd Hillman of the University of Alabama, in Huntsville, will describe a new method... light, travelling over very long distances, would have to spread out a bit if there was any uncertainty in time... "phase coherence"... Hubble space telescope... 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... Dr Lieu overestimated by a factor of several million.... Dr Lieu points out that Dr Ng's paper has not been accepted by a refereed journal, and is thus unreliable. Dr Ng retorts that he is surprised Dr Lieu's paper got past the refereeing process. Time, discrete or continuous, will tell...