Fascinating looking at the various orders of magnitude (in terms of length), from the size of the visible universe (~10^25) to the size of a quark (~10^-15), and all orders inbetween. But then I read about Superstring theory and how these strings are at the Planck length, around 10^-33. Why the huge jump from quark to string? Surely there must be loads of "stuff" in-between? Apologies if this is a daft question!