The story begins with a researcher called Giovanni Amelino-Camelia. Working on quantum gravity in Rome, he decided to find a theoretical solution to solve one of modern physics’ big problems – unexpectedly high energies of cosmic rays. To do this, he formed a new addition to the theory of special relativity.

The basis of doubly special relativity, which this is now called, is that the universe possesses two, not one absolute values. In Einstein’s original relativity, we have the speed of light as a constant, independent of the frame of reference for the observer. In doubly special relativity, there is also a threshold energy/length, which is true for all observers.

So far, so simple? But this small change makes a huge difference. By SR, the length of an object is entirely dependent on the particular observer. If I were moving at a different speed from you, I would see an object entirely differently. But in certain branches of physics, the laws of physics around an object are very dependent on its length, resulting in the absurd suggestion that the laws of physics are different for each person. In attempting to unify the different laws of quantum mechanics, where the Planck length/energy represents the point where quantum laws become apparent, this is especially problematic. If we follow DSR, and use the Planck energy as a universe absolute threshold, all observers can determine the laws of physics in the same way, and this problem is solved. The unification of quantum theory and relativistic theory is made a lot easier.

There are other implications too. Let’s go back to the original problem of the cosmic rays. These are thought to be extremely high energy particles from sources such as exploded stars, which travel through space at near light velocities, and are detected by the interactions they have in our atmosphere. Since these cosmic rays typically travel huge distances from space, they would collide with stray protons and other particles, and be destroyed. By using SR, it can be calculated that any cosmic particle with an energy of more than 5 * 10^19 eV, or about 3 J (the Greisen-Zatsepin-Kuzmin limit), would be destroyed by the time it got to earth. However, astronomers have detected rays with energies much more than that, and a possible explanation is to use DSR to calculate a new higher limit to such rays.

Indeed, the allure of the new theory is in its flexibility. Several versions of DSR have already been created using different applications of its fundamental principle. If certain assumptions are made, DSR does in fact reduce to conventional special relativity, allowing proponents to claim that it is the natural successor to the chain of progress that took us from Galileo to Einstein. Among the theory’s supporters are Lee Smolin, who believes it can be used to work on “loop quantum gravity”, which is based on space-time itself being composed of small discrete units, and Joao Magueijo, who is creating an alternative to the inflation theory of universal expanding using changing speeds of light.

This works by the fact DSR allows the energy of the photons themselves to in fact alter the speed of the photon. Blue light, for example, would travel at a slightly faster speed than red light. This difference is of course minute. Maguijo reasons that in the early universe, where photons had much higher energies than today, their velocities may in fact be significantly higher. Though this is in direct contradiction of Einstein, it does solve a lot of problems in cosmology.

But here is the crux of the problem. DSR could give us the keys to the universe. But it may not. One of the problems is with its lack of experimental justification. The only evidence that exists today for it is the high-energy cosmic rays. But opponents of the theory argue that this is not enough, and can be accounted for within experimental error. Other things that DSR solves can also be explained with other methods. “Elegance” is no excuse.

This problem is not helped by the personalities of the scientists involved. In particular Magueijo is an outspoken opponent of the current scientific establishment, whom he criticises for stifling change. In the same way, many physicists feel the need to argue against his dismissive attitude towards peer review, and other parts of the scientific method, and how he refuses to “play the game”.

But perhaps that will change. Though the really fundamental predictions of DSR are restricted to very small scales, such as 10^-35 m, much smaller than a proton, experiments are being devised with enough sensitivity to test this. The key is the 2006 GLAST satellite, designed to detect high-energy gamma ray bursts and measure the movement of particles with enough accuracy to find out the validity of the theory.