Science: Hazards of the Sun

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SOLAR eclipses are one of nature's most fascinating events —and also one of the most dangerous for observers. As more and more of the solar disk is blotted out, the sky darkens, and it becomes easier to gaze directly at the sun. While the visible light lessens, however, the pupils of the viewer's eyes dilate, allowing infra-red radiation from the still uncovered crescent of the sun to focus on his retinas. Although he feels no pain, the infra-red can quickly burn his retinas, causing irreparable damage to his vision. To avoid eye injury, medical authorities suggest that observers who look directly at an eclipse should do so only through at least two fully exposed photographic negatives that have been developed to maximum density. Sunglasses, welders' goggles or smoked glass do not provide adequate protection. To be completely safe, the eclipse watcher should turn his back to the sun and hold up a card with a pinhole. The sun's rays will be focused by the hole and projected as a sharp, safe solar image on any white surface a short distance away.