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The day before yesterday, I observed sunset while flying over the eastern Mediterranean. After the sun set, it seemed to 'continue' in front of the horizon. I managed to snatch a picture (sorry for bad quality, my phone's camera kept focusing on the dirt on the window, rather than on the image of the sun).

enter image description here

Picture was taken at 17:44 local time (15:44 utc), at an altitude of roughly 34,000 ft. It took quite a while before the image entirely disappeared.

What exactly am I seeing here? Is this a mirage? Or is the reflection of the sun on a far-away piece of sea, where the sun is still over the horizon? The weather was mostly clear.

Another user adds this similar photo:

enter image description here

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    $\begingroup$ I suspect that it's a reflection - I think the atmosphere is bending the light such that you can't see the Sun directly, but you can see the rays that have been bent by the atmosphere and then reflected off the sea. But I'm not at all sure about this. +1, it's a good question. $\endgroup$ – Nathaniel Feb 7 '15 at 13:45
  • $\begingroup$ Fantastic photo and question! $\endgroup$ – garyp Feb 7 '15 at 14:19
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Terrific photo - good that you were able to get it and don't apologize.

This diagram might explain it:

enter image description here

The sun is "below the horizon" as demonstrated by the green dashed line. A mirage can be formed by rays following the blue line (exaggerated scale, showing a layer where light can be reflected because of a sufficiently large change in density). If the sun reflected off the ocean at a point where the sun still shone, most likely you would have not seen the rays as they would follow the red line.

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    $\begingroup$ See en.wikipedia.org/wiki/Mirage for more information. And while you are at it, en.wikipedia.org/wiki/Green_flash $\endgroup$ – mmesser314 Feb 7 '15 at 17:32
  • $\begingroup$ Would the red line be impossible to see even when flying at an altitude of 11km? $\endgroup$ – Gx1sptDTDa Feb 9 '15 at 7:56
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    $\begingroup$ @Gx1sptDTDa the geometry of the picture implies that no: you see the sun originating from the surface, and only from there. If you were seeing the red line, you'd also see the Sun (the line which would connect the sun and the end of the red line doesn't cross the Earth). $\endgroup$ – Ruslan Jul 9 '18 at 16:57

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