Back in the Golden Days, string theory was in a bit of a theoretical pickle. For decades, theorists had poured their hearts and minds into the idea that the fundamental building blocks of reality are tiny, vibrating strings. This was a potentially revolutionary idea, capable of uniting all the forces of nature and all the building blocks of matter into a single, harmonious picture.
The pickle, however, was that there were five independent candidates for string theory, each one looking radically different than the others.