Variable fundamental constants

12 September 2010
Posted by Chris Smith.

Something which perplexes physicists is why the fundamental physical constants are what they are, why is the speed of the light about 300 000km/s, why is the charge on an electron 1.6 x 10-19C etc. and for that matter are they actually constant. This boils down to why does physics behave as it does, and is it the same everywhere?Artists concept of a quasar

The problem is that we can only do experiments to measure them precisely where we can get an experiment to - essentially just in our solar system. Otherwise we are limited to what we can observe. One fundamental constant we can observe very accurately is called the fine structure constant - this is a combination of the charge of an electron, the plank constant and the speed of light, and measures how electric field and quantum mechanics interact to create energy levels in an atom. And it can be measured by looking at the spectra of atoms, so it is very convenient for astronomers.

Close to the earth this seems to be constant, but John Webb and collegues from the university of New South Wales have been looking at some of the most distant sources we can see - quasars which are thought to be huge black holes accreting material billions of light years away. In 2003 they discovered that the fine structure constant appears to have increased about 1 part in 200 000 since the light left the quasars.

But this study was only done in the northern hemisphere, they have recently done a simlar study in the southern hemisphere using the Very Large Telescope in Chile, which has found something possibly even more interesting - the result was that to the south the fine structure constant was changing by about the same amount as you go back in time but it was decreasing rather than increasing.

They have found a fairly strong signal but only time and more experiments will tell if it continues to hold up. If it does it might explain why fundamental physics is so well suited to life, essentially because it varies throughout the universe and our form of life has only developed in the part of the universe where it can survive.

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