In this respect early youth is exactly like old age; it is a time of waiting for a big trip to an unknown destination. The chief difference is that youth waits for the morning limited and age waits for the night train.
Intellectuals, academics, writers and poets were an important force in the early groups of volunteers. They had the means to get to Spain and were accustomed to travelling, whereas very few workers had left British shores.
General relativity is the cornerstone of cosmology and astrophysics. It has also provided the conceptual basis for string theory and other attempts to unify all the forces of nature in terms of geometrical structures.

