Lesson plan
Shadow bands
Shadow bands are thin, wavy lines of alternating light and dark that can be seen moving and undulating in parallel on plain-coloured surfaces immediately before and after a total solar eclipse. They are caused by the refraction by Earth's atmospheric turbulence of the solar crescent as it thins to a narrow slit, which increasingly collimates the light reaching Earth in the minutes just before and after totality. The shadows' detailed structure is due to random patterns of fine air turbulence that refract the collimated sunlight arriving from the narrow eclipse crescent. The bands' rapid sliding motion is due to shifting air currents combined with the angular motion of the Sun projecting through higher altitudes. The degree of collimation in the light gradually increases as the crescent thins, until the solar disk is completely covered and the eclipse is total. Stars twinkle for the same reason. All light passing through the Earth's atmosphere encounters tiny disturbances in temperature, pressure, and humidity. These disturbances change the air's refractive index, so that the light essentially passes through innumerable tiny prisms. Thus, the entire sky essentially "dances" randomly at the scale of the disturbances.…
Article summary
Shadow bands are thin, wavy lines of alternating light and dark that can be seen moving and undulating in parallel on plain-coloured surfaces immediately before and after a total solar eclipse. They are caused by the refraction by Earth's atmospheric turbulence of the solar crescent as it thins to a narrow slit, which increasingly collimates the light reaching Earth in the minutes just before and after totality. The shadows' detailed structure is due to random patterns of fine air turbulence that refract the collimated sunlight arriving from the narrow eclipse crescent. The bands' rapid sliding motion is due to shifting air currents combined with the angular motion of the Sun projecting through higher altitudes. The degree of collimation in the light gradually increases as the crescent thins, until the solar disk is completely covered and the eclipse is total. Stars twinkle for the same reason. All light passing through the Earth's atmosphere encounters tiny disturbances in temperature, pressure, and humidity. These disturbances change the air's refractive index, so that the light essentially passes through innumerable tiny prisms. Thus, the entire sky essentially "dances" randomly at the scale of the disturbances.…
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Discussion questions
- Summarise the article in your own words. Which single claim would you verify first, and why?
- Which claim in this article is most likely to be revised as the sources update? How would you check its current status?
- If two sources disagreed about one of these facts, what would you need in order to trust one over the other?
Bibliography
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Key claims and bibliography are generated from the same tracked claims and sources as the article page.