The idea of a variable speed of light, championed by an angry young scientist, could one day topple Einstein's theory of relativityby Paul Davies / April 20, 2003 / Leave a comment
Einstein’s famous equation E=mc2 is the only scientific formula known to just about everyone. The “c” here stands for the speed of light. It is one of the most fundamental of the basic constants of physics. Or is it? In recent years a few maverick scientists have claimed that the speed of light might not be constant at all. Shock, horror! Does this mean the next Great Revolution in Science is just around the corner?
Well, maybe. According to one of those scientists, Portuguese-born, London-based Jo?o Magueijo, cracks are appearing in Einstein’s theory of relativity – the cornerstone of our present understanding of space, time and gravitation. In “Faster than the Speed of Light”(Heinemann) he describes his personal journey through this controversial and emotionally supercharged field.
Magueijo got into the subject while puzzling over the smoothness of the universe, a property illustrated by the recent results from the satellite WMAP (Wilkinson Microwave Anisotropy Probe), showing a snapshot of the universe just 380,000 years after the big bang (see picture). Significantly, the infant cosmos appears uniform in temperature and density to about one part in 100,000.
The mystery here is that light can have travelled no more than 380,000 light years by that epoch, yet different patches of the sky shown in the snapshot might be millions of light years apart. As no force or influence can travel faster than light, these various patches can never have been in causal contact. So why are they so similar?
Magueijo has an answer. Perhaps light travelled much faster in the past, enabling forces to propagate more quickly. In that case, widely separated regions of the universe could have pushed and pulled on each other, and thus smoothed out their differences. The theory is easy to state, but it flies in the face of much accepted wisdom. For a start, cosmologists already line up behind a very different explanation for cosmic smoothness, called inflation. According to this scenario, the universe jumped in size by an enormous factor during the first split second. Any primordial irregularities would then have been stretched to oblivion. WMAP lends strong support to inflation.
More worryingly, constancy of the speed of light is central to the theory of relativity and the other areas of modern physics that this theory penetrates. Physicists will give up this key set of ideas only after a bitter struggle. Magueijo describes just what a…