This entry examines the parable in Surah an-Nur 24:40, which pictures darkness within a deep sea covered by waves upon which are further waves and clouds, and whether its imagery aligns with modern accounts of light attenuation with depth and of internal waves.
The source text
أَوْ كَظُلُمَـٰتٍ فِى بَحْرٍ لُّجِّىٍّ يَغْشَىٰهُ مَوْجٌ مِّن فَوْقِهِۦ مَوْجٌ مِّن فَوْقِهِۦ سَحَابٌ ۚ ظُلُمَـٰتٌۢ بَعْضُهَا فَوْقَ بَعْضٍ إِذَآ أَخْرَجَ يَدَهُۥ لَمْ يَكَدْ يَرَىٰهَا ۗ وَمَن لَّمْ يَجْعَلِ ٱللَّهُ لَهُۥ نُورًا فَمَا لَهُۥ مِن نُّورٍ
“Or [they are] like darknesses within an unfathomable sea which is covered by waves, upon which are waves, over which are clouds - darknesses, some of them upon others. When one puts out his hand [therein], he can hardly see it. And he to whom Allah has not granted light - for him there is no light.”
Qur'an 24:40 · Saheeh International
What was understood in the seventh century
The verse is a parable about the spiritual state of those who reject faith, using the image of a deep sea in layered darkness, with waves above waves and clouds above them. Its stated purpose is a moral lesson: one to whom God grants no light is left in compounded darkness, so deep that "when one puts out his hand, he can hardly see it." The imagery serves this point, not a survey of the ocean.
In the seventh century there was no means of diving to great depth or of measuring how light fades as one descends. The picture reflects the intuition, available to any seafarer, that deep water is dark and that the sea's surface is turbulent under storm cloud. That intuition is here framed for a spiritual argument rather than offered as a description of the water column.
The layered structure the verse names, waves, then further waves above them, then clouds above those, and "darknesses, some of them upon others," is what later readers connect to the physical stratification of the sea and sky. In its own setting the layering is primarily rhetorical, building an image of darkness heaped on darkness.
The modern correspondence
Modern oceanography establishes that sunlight is progressively absorbed and scattered with depth. The sunlit, or euphotic, zone gives way to a dim twilight, or dysphotic, zone, and, below roughly 1000 metres, to the aphotic zone of near-total darkness where sunlight does not reach. The fading of light with depth is gradual and measurable, and colours drop out in sequence as one descends.
Oceanographers also document "internal waves," which travel along the interface between water layers of different density, beneath the surface waves that are visible from above. Some commentators connect this subsurface layering, waves moving under waves, to the phrase "waves upon which are waves," and read the further clause "over which are clouds" as completing a vertical stack from cloud to surface wave to internal wave to lightless depth.
These features were characterised only with modern instruments and submersibles from the nineteenth and twentieth centuries; the sequencing of light zones, in particular, depended on instruments able to measure how quickly illumination falls off with depth, which no seventh-century observer possessed. The references below document how far light travels in the ocean and what internal waves are.
Considerations and counterpoints
Critics stress that the verse is a simile for spiritual blindness, not a scientific statement, and that "darkness in the deep sea" and "waves" are commonsense images available to anyone who has known the sea. Reading precise light-attenuation zones or subsurface internal waves into "waves upon waves" is, they argue, retrofitting modern science onto poetic language whose plain sense is moral. The tier assigned here reflects that the passage is explicitly a parable and that the internal-waves reading, while striking, is interpretive rather than demanded by the text.
Credibility rating: Tier 2 · Interpretive — Authentic clear text whose depiction of deep darkness and layered waves aligns with modern findings, but the passage is explicitly a moral parable and the 'internal waves' reading is interpretive.