Photo of the month

摘要

Lightning crackles through Earth's skies over 1.5 billion times each year, with a quarter of those bolts being cloud-to-ground (CG). In the United States, typically 30 million CGs strike annually, with July being the peak month. While the channel to ground is only roughly the thickness of a finger, currents can easily reach 25 kiloamps and sometimes 10-20 times that, with temperatures peaking at 50,000 ℉ (much hotter than the sun's surface). In recent decades, public education and awareness campaigns have greatly lowered U.S. human casualties from lightning strikes, though NOAA estimates that nearly 30 people are still killed yearly, and upward of 10 times are seriously injured. Global fatalities are hard to quantify, but some experts believe that over 10,000 lives are lost annually. Especially vulnerable is Africa, and especially its children, with many of their schools not yet equipped with effective lightning protection (though efforts are underway to improve on this situation). Lightning's kinder side produces the beautiful and awesome spectacles it paints in our skies. It has long inspired poets and artists. Recent research (by Professor Terry Nathan suggests that the first known daguerreotype image of a flash streaking through the sky was captured by a stroke of luck over St. Louis, Missouri, on June 18, 1847, by one Thomas M. Easterly. Modern cameras render lightning photography far less of a technical challenge, allowing for considerable artistry in the way we portray these giant sparks. On September 15, 2017, Roberto Porto set up his DSLR using a 15-mm lens, for the 30-second time exposure (below) as a storm peppered Costa Adeje, Tenerife, Canary Islands. The attachment points of eight CGs are clearly visible.