context: He produced artificial lightning, with discharges consisting of millions of volts and up to 135 feet long. Thunder from the released energy was heard 15 miles away in Cripple Creek, Colorado. People walking along the street observed sparks jumping between their feet and the ground. Sparks sprang from water line taps when touched. Light bulbs within 100 feet of the lab glowed even when turned off. Horses in a livery stable bolted from their stalls after receiving shocks through their metal shoes. Butterflies were electrified, swirling in circles with blue halos of St. Elmo's fire around their wings.
question: ఎంత దూరంలో ఉన్నా కృత్రిమ ఉరుములు వినిపించాయి.
answers: 15 miles 15 miles 15 miles away