Surah 81:15–19:
So I swear by the retreating stars—those that run and hide—and by the night as it closes in, and by the dawn when it breathes: indeed, this is a word of a noble messenger.
The Surah introduces an elegant, rhythmic oath swearing by a specific celestial phenomenon: "So I swear by the retreating stars—those that run and hide."
The Philological Meaning: The words khunnas (those that shrink back/retreat) and kunnas (those that sweep into their hiding places) refer specifically to the five visible planets known to the ancient world (Mercury, Venus, Mars, Jupiter, and Saturn).
The Retrograde Apparition: To an ancient astronomer observing the night sky from a flat earth, planets appeared to exhibit retrograde motion—moving forward, then suddenly slowing down, appearing to drift backward (khunnas), and eventually disappearing or "hiding" (kunnas) behind the blinding glare of the sun.
The Critique: While early Muslim commentators (such as Al-Tabari) marvelled at these verses as deep cosmic mysteries, a secular historian notes that this is simply the poetic mythologization of local, pre-Copernican astronomy. The text describes a visual illusion caused by Earth's own orbit overtaking outer planets. By framing this optical quirk of geocentric observation as a supreme divine oath, the Quran locks its narrative voice into the limited astronomical understanding of 7th-century observers who mistook planetary perspective for literal cosmic hide-and-seek.