Because this is what wikipedia sais to this topic. "Iridescent" debuted at #1 on the US Alternative Songs and #1 on the US Rock Songs." I know that wikipedia isn't always right, but if it is in this case, it would be their 11 no 1 hit on the alternativ and their 3 hit on the rock song charts (after New Devide and The Catalyst) Does anyone know the answer? Source: http://en.wikipedia.org/wiki/Iridescent_(song)