Explore a groundbreaking theory on the spontaneous formation of sand dunes and related bedforms in this 55-minute lecture. Delve into the concept that smaller sediment accumulations outpace larger ones due to surface-to-volume ratio differences. Discover how this principle leads to bed shortening along the current's direction, resulting in the formation of ripples and dunes. Examine the validation of these ideas through the first-ever accurate predictions of dune speeds derived solely from length and surface area measurements.