Smolin argues from the outset that viable hypotheses must lead to observable consequences by which they can be tested and judged. That is, they have to be falsifiable. Newton's theory of gravitation, for example, could later account for the orbit of Halley's Comet – not just those of the Moon and planets for which it was originally formulated. But string theory by its very nature does not allow for such probing, according to Smolin, and therefore it must be considered as an unprovable conjecture.Or is it?
In 2006, string theorist Allan Adams of MIT in Cambridge, US, and others offered a more promising check. They showed that some particle collisions could reveal whether certain fundamental assumptions underlying string theory are wrong.All we can do is wait and see.
Now, another team has shown that the energies needed to reveal such effects are achievable at the LHC, which is being built in Geneva, Switzerland. The team was led by Jacques Distler of the University of Texas in Austin, US.
One of string theory's assumptions comes from Einstein's theory of relativity – that the speed of light is the same for all observers, a principle called Lorentz invariance.
This principle – and three others underlying string theory – determine how strongly particles called W bosons, which transmit the weak nuclear force, interact.
If these interactions are below the strength calculated by Distler's team, it would signal that one of the assumptions built into string theory is incorrect and that therefore string theory itself is wrong, the researchers say.