For millennia, humans have been fascinated with the ghostly green and red curtains of light that shimmer across the heavens on dark, clear nights. Ancient peoples saw these displays as souls of the dead, the torches of the spirits and as harbingers of war. Barely 100 years ago, scientists finally learned that an aurora is created when the Earth's magnetic field is bombarded with charged particles from the sun. When the charged particles collide with oxygen in the atmosphere, auroras with yellows, greens and reds appear. Collisions with nitrogen result in bluish colors. However, our understanding of the physics behind auroras has not detracted from their wonder. Auroras is filled with 80 photographs of one of nature's greatest spectacles, complete with captions that reflect on the folklore, science and beauty of the northern lights. The book poses and answers the many scientific questions about auroras: Why are auroras usually seen only at high latitudes? How do scientists study them? What causes the different colours? Why are massive auroras often followed by blackouts and computer system crashes? Auroras is where cutting-edge science meets the stuff of dreams.