The Nature of Extra Dimensions and String Theory

In quantum gravity, the concept of the size of extra dimensions or their dimensionality may not exist. Near the Big Bang, the dimensions of space-time remain unknown. Brandenburger and Vafah proposed a scenario where all nine dimensions were compact and small, suggesting that strings in three dimensions intersect, unlike in four or more dimensions where intersections are rare. This led to the theory of three-dimensional space growing as strings unwound due to frequent intersections, known as the Brandenburger-Vafah cosmology scenario.