The superstring saga has its roots in the prehistory of particle physics: the 1960s. In Chapter 13, I recounted how Gabriele Veneziano toyed with formulae for the strongly interacting mesons. It took several years before it became clear that these are exactly the expressions obtained if each of these mesons is viewed as being a kind of rope with a quark at one end and an antiquark at the other. The ropes can be stretched ad infinitum, because stretching them adds energy to them, which will be turned into matter: that is, more rope.

The reason why Veneziano's formula described the properties of mesons so well was that this really is what mesons look like, approximately. Except that the ropes are not infinitely thin, they are fat ropes, formed by the pattern of strong force lines between the quarks. At higher energies Veneziano's formula becomes less accurate because features at smaller distance scales are being probed and then we see that the flux tubes produced by the strong force are no longer like strings. Rather than Veneziano's model, ‘quantum chromodynamics’, that is, the SU(3) color gauge theory, was bestowed with the honor of being regarded as the prime theory for the mesons and the baryons.

But this did not imply that Veneziano's expressions were forgotten. Could one not construct an alternative theory for some kinds of particles that really consist of ideal, unbreakable ‘strings’? In the 1970s physicists began to investigate whether the theory of mutually interacting strings could be improved.