In a previous post, I explained why a “blood moon” eclipse is tinted red… this image of a sunrise might explain it a little better. This was taken at the East Fork Overlook at milepost 418.3 along the Blue Ridge Parkway. On the tripod, the camera was at an elevation of nearly exactly 5,000 feet… that makes the horizon where the Sun popped up roughly 85 miles away from the lens. This was shot fullframe with a 400 mm lens, so the distance is compressed, but it shows the effect of denser atmosphere concerning the penetration of sunlight.

Officially, according to the European Space Agency, Earth’s atmosphere extends to 60 miles straight overhead. The atmosphere consists of gasses, mostly nitrogen and oxygen, water vapor, and dust. On a clear day, sunlight when the Sun is at zenith is not merely white but scattered throughout the color spectrum. The reason a leaf on a tree is green is because that leaf absorbs all wavelengths of light except green, which is reflected. The sky is blue not because it’s reflecting blue, but rather that it absorbs only blue light and is transparent… of all the colors, blue has the shortest wavelength of visible light. All the longer wavelengths just shoot right through.

Looking directly to the horizon as in this image, the depth of the atmosphere is nearly 145 miles… more atmosphere absorbs more light, yet the longer wavelength of red light easily affects the visible light of this sunrise. The red band on the Sun is due to a layer of vapor in the distance which scatters just about all visible light but red. Red pouring off that Sun sitting on the distant ridge looks quite like a beacon… it’s bright enough that the fog between mountaintops is reflecting it a bit. Other than evident vapor in the air to the east, there was no cloud cover in that direction on this morning. There’s a steep cliff to my back as I shot this, so I couldn’t tell about cloud coverage in that direction… but if there were clouds in that direction, they would have reflected the deep red light apparent here, and perhaps even more as they would be even further from the horizon. I hope this makes sense.