Picture a herd of sheep or cattle emerging from a shed or barn to graze a field. They head straight out of their digs to the pleasure of the pasture pretty much as one entity, but as the land opens up and the “grass gets greener” they disperse randomly in a motion that has neither rhyme nor reason. Individual animals depart at different angles from the herd and then at different angles from their original departure and so on until “the cows come home.”