As scientists prepare for the most significant solar eclipse of the century on July 22, noted heliologist Dr Hari Om Vats is demystifying the shadow bands that occur before and after a solar eclipse. The associate professor at the Physical Research Laboratory (PRL) was in Vadodara to talk to the budding astronomers and students about how shadow bands render valuable data about the atmosphere, especially about pollution. In a tête-à-tête with Anupam Chakravartty, Dr Vats explained the importance of studying the shadow bands.

* A theory suggests that shadow bands are not just visual events but also sonic, as the moon is believed to move at a supersonic speed, creating various sound waves during the solar eclipse. What do you think about this?
Shadow bands are constructive and destructive interferences of light before and after a solar eclipse is noticed in areas of low elevation. In layman’s words, it is the play of light and shadow preceding and succeeding a total solar eclipse noticed from earth. It is merely a visual spectacle that can render important data about solar eclipse and the atmosphere, including pollution in the atmosphere. That shadow bands are a sonic event is yet to be proved, as it is not the moon but its shadow that moves at a supersonic speed during the time of eclipse.

* What is India’s contribution to the study of shadow bands so far?
Maitri, our station in Antarctica, got the first chance to study shadow bands on November 23, 2003 for 11 minutes at a stretch, which is extremely rare. It happens in about 1,000 years. Many other countries had studied that eclipse, but for us it was an exclusive opportunity. As Maitri is located on the edge of the Indian Ocean at a gradient of 12 degrees, we could witness six minutes of shadow bands before the event and four minutes after it. Two of my colleagues, S P Bagare and S M Bhandari, and I had suggested the Indian government that we should study these bands.

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