Does string theory only have one parameter? I was under the impression that you also had to insert some very complicated underlying geometry into spacetime (the extra dimensions), which I would count as more parameters.
You would be somewhat right, this is known as the landscape problem. Technically string theory has no free dimensionless parameters (by the formal definition, values which need to be determined experimentally).
edit: to expand, the landscape problem is more about finding the right parameters for compactification (folding up the geometry) that produce the universe we all know and love, or at least a realistic one. This makes them similar to free parameters.
edit: to expand, the landscape problem is more about finding the right parameters for compactification (folding up the geometry) that produce the universe we all know and love, or at least a realistic one. This makes them similar to free parameters.