The power to bend light

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While I was taking a photograph of this rather unremarkable sunset, the light was illuminating the escarpment behind me. When the disc of the sun dips below the horizon, it is actually a whole diameter of the visible sun below that point. The effect we observe is caused by the bending of the sun's light rays by the atmosphere. I can sense your disbelief: don't take my word for it—Phil Plait explains on the Discover Magazine website with the help of Stephen Fry and the QI (Quite Interesting) team. The times recorded by the camera were 18:20 (above) and 18:21 (below) on Mon. 03 Mar. 2014, when the height of the hill kept it in the bent sunlight.

The published sunset time was 18:30 and we usually lose around 15 minutes because of our location. This raises the question of who publishes those times and what they mean: do the published times presume we are at sea level and that we are observing the sunset below the curvature of the earth in that imaginary place? I used the word "imaginary" because at our latitude and longitude the elevation is around 3,000 feet above sea level. Shouldn't that give us more time in the sunshine, not less, in the same way the escarpment benefits? The topography must be a more important factor than the theoretical geometry.

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