Wyatt White, left, 11, of China, and Ryan Violette, 10, of Action, observe a fire they started Sunday with magnifying glasses during a physics display at the annual 4-H Days at the Windsor Fairgrounds. Nearly 500 people attended the annual agricultural gathering held from Thursday until Sunday to exhibit animals, attend workshops and burn a few pieces of a paper. The Mainely Physics Road Show, with the University of Maine, taught children at 4-H Days about electric currents and gravity while closely monitoring boys refracting light with magnifying glasses.