The Qur'anic Description of Day and Night

The Holy Qur'an frequently addresses the phenomena of day and night, describing them not just as mere chronological markers, but as fundamental and intricate signs (Ayāt) of the Creator’s majesty and wisdom. The rich vocabulary employed—including alternation, mergence, covering, and precise measurement—points toward a system of mechanics that was scientifically confirmed only many centuries later.

I. The Fundamental Principle: Alternation and Divine Measurement

The most basic function of day and night is their continuous, purposeful change. The Qur'an repeatedly identifies the alternation (ikhtilāf) of night and day as an irrefutable sign for those with understanding:

"Verily! In the creation of the heavens and the earth, and in the alternation of night and day, and the ships which sail through the sea... are indeed Ayât (signs) for people of understanding." (HQ: 2:164, also 3:190, 10:6, 23:80)

This alternation serves as a continuous lesson for those seeking gratitude and remembrance: "And He it is Who has put the night and the day in succession, for such who desires to remember or desires to show his gratitude." (HQ: 25:62). The process is not random, but precisely orchestrated, indicating a measured, controlled system: "Allâh causes the night and the day to succeed each other (i.e. if the day is gone, the night comes, and if the night is gone, the day comes, and so on). Truly, in these things is indeed a lesson for those who have insight." (HQ: 24:44). The ultimate control of time is affirmed: "And Allâh measures the night and the day." (HQ: 73:20).

Furthermore, the verses emphasize the complementary nature of this duality, where the night is often depicted as covering the day, and where neither celestial body can outstrip the other:

"He brings the night as a cover over the day, seeking it rapidly..." (HQ: 7:54, also 13:3) "a sign for them is the night, We withdraw therefrom the day, and behold, they are in darkness." (HQ: 36:37) "It is not for the sun to overtake the moon, nor does the night outstrip the day. They all float, each in an orbit." (HQ: 36:40)

II. The Description of Mergence and Celestial Mechanics

Perhaps the most compelling descriptions are those detailing the gradual change in the duration of light and darkness, a phenomenon that precisely mirrors the effects of the Earth’s axial tilt and orbital motion. The Qur'an uses the word yūlij (merges or enters) to describe the gradual shift of time between the two:

"You make the night to enter into the day, and You make the day to enter into the night (i.e. increase and decrease in the hours of the night and the day during winter and summer)..." (HQ: 3:27, also 22:61, 31:29, 35:13, 39:5)

This language of "mergence" accurately depicts the decrease in the hours of night being added to the hours of the day (the shift towards summer) and vice versa (the shift towards winter). This subtle change, which causes the variation in day length and the succession of the seasons, is a direct result of the Earth’s rotation around the Sun on a fixed, inclined axis—a fact only comprehensively understood in modern astronomy.

III. Confirmation through Astronomical Discovery

The detailed Qur'anic descriptions found throughout the text take on added significance when compared against the history of scientific discovery.

The foundational proof of the Earth’s daily rotation around its axis, which causes the instantaneous succession of day and night, was first definitively demonstrated by Jean-Bernard-Leon Foucault in 1851 with his famous pendulum experiment.

Subsequently, astronomical research confirmed that the length of the day and night varies because the Earth’s rotational axis is tilted by 23.5 degrees relative to its orbital plane. As the Earth revolves around the sun, the angle at which the sun rises and sets constantly deviates—moving from the equator (at the equinoxes) toward its northernmost point (Tropic of Cancer) in summer, and southernmost point (Tropic of Capricorn) in winter. This perpetual shift in the points of sunrise and sunset leads to the continual mergence of night into day, increasing or decreasing their respective lengths across the year. This scientific reality validates the Qur'anic affirmation of absolute mastery over space and time:

"So I swear by the Lord of all [the three hundred and sixty (360)] points of sunrise and sunset in the east and the west that surely We are Able..." (HQ: 70:40)

This oath, mentioning "Easts and the Wests" in the plural, acknowledges the multiplicity of sunrise and sunset points observable throughout the year due to the Earth's orbital movement and axial tilt.

IV. The Wisdom of the Phenomenon

The final dimension of these verses is their focus on the practical blessing and function of this celestial order. The Creator did not make the day and night continuous, but subjected them to the rhythmic alternation to provide rest and facilitate activity for humankind:

"He it is Who has appointed for you the night that you may rest therein, and the day to make things visible (to you). Verily, in this are Ayât (signs) for a people who listen (i.e. those who think deeply)." (HQ: 10:67, also 27:86, 40:61)

The indispensable nature of this balance is highlighted through a hypothetical challenge:

"Say (O Muhammad SAW): 'Tell me! If Allâh made night continuous for you till the Day of Resurrection, who is an ilâh (a god) besides Allâh who could bring you light? Will you not then hear?'" (HQ: 28:71) "Say (O Muhammad SAW): 'Tell me! If Allâh made day continuous for you till the Day of Resurrection, who is an ilâh (a god) besides Allâh who could bring you night wherein you rest? Will you not then see?'" (HQ: 28:72)

The complexity of the day-night cycle, described with such precision in the Qur'an centuries before Foucault's experiment or the full understanding of the 23.5-degree axial tilt, stands as a continuing testament to the source of its revelation.