Bumbershoot Saturday is in full swing. The great Shabazz Palaces (5:45 p.m.) or Pickwick (6:00 p.m.) dilemma is yet to come. For now the weather is nothing short of magnificent, and Spectrum Dance Theater (remember, Bumbershoot is an arts festival) just presented a world premiere to a packed Bagley Wright theater. Snapshot audience reviews: “Wow, that was awesome!” and “Way cool!” Out at the Fountain Lawn stage, a rapper explains that science is the new thing for 2012: “It’s not black or yellow any more,” he explains. “It’s boron and photons.”