Great Plains Solstice Twilight

Last month I drove across the United States, coast-to-coast back-and-and forth diagonally, 8000 miles through 18 states, as in the animation below. Amazing was driving through the Great Plains of the North American flatland with uninterrupted 360° horizons as the sun slowly set and civil, nautical, and astronomical twilight seemed impossibly long. The explanation was the nearness of the summer solstice, when Earth’s tilt extends the sunset by spinning an Earth-bound observer diagonally across the day-night terminator, which is blurred by atmospheric refraction, as illustrated in the diagrams below.