空は、レイリー散乱と呼ばれる現象のために、夕方（そして日の出の間）にオレンジ色の赤に見えます。これは、太陽光が地球の大気中の分子や小さな粒子と相互作用し、あらゆる方向に日光を散らしたときに発生します。空の色は、最も効果的に散在する光の波長に依存します。夕方、太陽が地平線に近づくと、太陽光は大気の厚い層を通過する必要があります。より伸びた経路を移動すると、より短い波長（紫、青、緑）のほとんどは視界から散らばっています。赤やオレンジのような長い波長は、散在するほど少なく、目に到達する可能性が高くなります。これが、日の出と日没時に空がオレンジ色に見える理由です。
The sky appears orange-red in the evening (and also during sunrise) due to a phenomenon called Rayleigh scattering. This occurs when sunlight interacts with molecules and small particles in the Earth's atmosphere, scattering the sunlight in all directions. The color of the sky depends on the wavelengths of the light that are scattered most effectively. In the evening, as the Sun approaches the horizon, the sunlight has to pass through a thicker layer of the atmosphere. As it travels through a more extended path, most of the shorter wavelengths (violet, blue, and green) are scattered out of view. The longer wavelengths, like red and orange, are scattered less and are more likely to reach our eyes. This is why the sky appears orange-red during sunrise and sunset.