For very distant sources, the light that is absorbed by dust and reradiated into the far-infrared is shifted by the expansion of the universe to submillimeter wavelengths.

• 非常遥远光源所发出的光，经尘埃吸收后再以远红外光辐射出来，会受到宇宙膨胀的影响而移到次毫米波段。