Is the proton losing weight, or has the fabric of the Universe changed? [View All]

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Published online: 20 April 2006; | doi:10.1038/news060417-7
A universal constant on the move

It seems that nothing stays the same: not even the 'constants' of physics. An experiment suggests that the mass ratio of two fundamental subatomic particles has decreased over the past 12 billion years, for no apparent reason.

The startling finding comes from a team of scientists who have calculated exactly how much heavier a proton is than an electron. For most purposes, it is about 1,836 times heavier. But dig down a few decimal places and the team claims that this value has changed over time.

The researchers admit that they are only about 99.7% sure of their result, which physicists reckon is a little better than 'evidence for' but not nearly an 'observation of' the effect. If confirmed, however, the discovery could rewrite our understanding of the forces that make our Universe tick.

Fickle forces

This is not the first time physicists have suspected physical constants of inconstancy.

In 1937, the physicist Paul Dirac famously suggested that the strength of gravity could change over time. And arguments about the fine-structure constant, , have raged for years (see 'The inconstant constant?'). The fine-structure constant measures the strength of the electromagnetic force that keeps electrons in place inside atoms and molecules.
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http://www.nature.com/news/2006/060417/full/060417-7.html