Fireworks: Not just for nighttime anymore. Artist Cai Guo-Qiang lit up the Doha, Qatar horizon last week with an “explosion event’ that shot rainbow-colored gunpowder into the desert sky near the Arab Museum of Modern Art. The explosions, which are so intense that they sound like a racecar going around a track at full speed, are controlled by microchips. Guo-Qiang also designed the fireworks for the Beijing Olympics closing ceremony.