The Effects of Gravity in a String Theory

Around the middle of the 1970s, it was noticed that all known string theories automatically included a massless spin-2 particle. From this perspective, any string theory would automatically be a theory of quantum gravity. But in its original form, string theory still had a lot of questions that were unanswered or even problematic. So if you knew exactly how a given string was vibrating, you could in principle work out how heavy that thing would be and what kind of charges does it carry.