Look inside an Egyptian coffin lid and there is often a naked woman stretched the full length of it, arms extended above her head, body covered in stars, looking down at whoever is lying inside. That is Nut, and the placement is the whole theology in one design decision: the dead are laid in her body, so that what happens to the sun each night can happen to them.
She is the sky, arched over the earth on fingertips and toes, with Shu standing beneath holding her up and Geb lying below her. On temple ceilings and on the undersides of sarcophagus lids she is drawn in profile, elongated far beyond human proportion, and the elongation is the point — she has to span the world.
Swallowed at evening, born at dawn
She swallows the sun each night. It passes through her body in darkness, and at dawn she gives birth to it from between her thighs, which Egyptian art shows without any coyness whatever: the sun disc emerges, sometimes with rays falling onto the horizon or onto a figure of Hathor below. The stars follow the same route, disappearing into her mouth at dusk and being born again.
This produced an obvious theological problem that Egyptian texts noticed and worried at. If she eats her own children every evening, she is doing something monstrous, and some passages call her the sow that eats her piglets — an image of the sky as devourer, uncomfortable and not smoothed over. Egyptian religion had space for a mother figure who is also, in one respect, an eater of what she bore.
The Book of Nut, a cosmographic composition preserved in the Osireion at Abydos and later on papyri, treats the sequence technically rather than narratively: it is concerned with the decans, the thirty-six star groups whose successive risings divided the night and produced the Egyptian hours, and with where each decan spends its seventy days of invisibility before reappearing. The document is closer to an astronomical handbook with a goddess drawn around it than to a myth. Those same decans passed into Hellenistic astrology after the Ptolemaic period, one of the few places where Egyptian sky-lore genuinely feeds a later system — an inheritance visible in how the western horoscope tradition was assembled.
Five days that did not exist
The Egyptian civil calendar ran twelve months of thirty days, giving 360, with five extra days added at the end — the epagomenal days, on which the five great gods were born.
The story explaining them survives only in Greek. Plutarch's De Iside et Osiride, composed roughly two millennia after the calendar it accounts for, is the sole narrative source, and its author knew Egypt at second hand. In his telling, Ra discovers Nut's pregnancy and curses her so she cannot give birth in any month of any year; Thoth plays a board game with the moon, wins a seventieth part of each of its illuminations, assembles five whole days out of the winnings, and adds them outside the year. On those days Osiris, Horus the Elder, Set, Isis and Nephthys are born.
The days themselves are entirely Egyptian and very old; their association with the five births is Egyptian too. The gambling narrative, in this form, is Plutarch's. Egyptians regarded the five as dangerous — a gap in the ordered year — and protective rituals cluster on them, including material addressed to Sekhmet and her messengers at the turn of the year.
The calendar's real defect was elsewhere: 365 days with no leap day drifts about a day every four years, so the civil year rotated slowly through the seasons, taking roughly 1,460 years to return to alignment. Egypt knew this and declined to fix it for millennia; Ptolemy III's Canopus Decree of 238 BCE proposed a sixth day every four years and was not implemented, and the correction only stuck under Augustus.
Sow, cow, and woman
Her three forms carry three different statements. As a woman she is the arch of the sky. As a cow she is the vehicle: in the Book of the Heavenly Cow, when the ageing Ra withdraws from a rebellious humanity, he departs on her back, and she rises so high she becomes dizzy and needs Shu and eight heh gods to steady her legs — which is how the four legs of the sky cow come to be the four supports of the world. As a sow she is the devouring aspect, and the image appears on amulets.
Her body is a place with contents: stars named and mapped, the sun's route, the Duat itself in some accounts placed inside her rather than beneath the ground. That is one of the several coexisting Egyptian answers to where the night journey happens, and Egyptian cosmology never required them to be reconciled.
The tree, and the dead
She overlaps with the sycamore-fig goddess who leans out of the tree to hand bread and water to the dead — a role more usually Hathor's, and the two are frequently interchangeable in that scene. In the Pyramid Texts she gathers the dead king into herself and makes him an imperishable star; in Middle Kingdom coffin decoration she addresses the deceased directly with a spread-wing gesture. The formula that she spreads herself over her child is used of Osiris and then of every dead person, which is how a cosmological goddess became the standard figure of funerary consolation.
She has no significant temple of her own. Like Ma'at and Geb, she is structurally everywhere and institutionally nowhere.
Questions about the sky goddess
Is "Nuit" the same goddess?
Nuit is a French-influenced spelling of the same name, and it became fixed in English through Aleister Crowley's Book of the Law of 1904, where Nuit is a central figure in a system Crowley devised. That system's Nuit — infinite space, the sum of possibility — is not the Egyptian goddess in anything but name, and the two should be kept apart. The Egyptian material is about a sky, a sun, a calendar and a coffin lid.
Why is she shown naked when Egyptian goddesses usually are not?
Because the figure is a cosmic body rather than a person in a scene, and clothing would obscure the star field, the sun's passage and the pregnancy that the image is about. Egyptian art dresses deities according to what the picture needs to convey; the same goddess in a temple relief receiving offerings wears a sheath dress like any other.
Did Egyptians name constellations on her body?
They did, and the system is not ours. Astronomical ceilings — in the tomb of Senenmut, in the Ramesseum, at Dendera — show figures including the Meskhetiu, a bull's foreleg corresponding roughly to the stars of the Plough, a hippopotamus goddess usually identified with part of Draco, a crocodile, a falcon-headed figure and a giant. The decans occupy the southern band. Very few Egyptian star groups map cleanly onto Greek constellations, and the identifications beyond the foreleg are argued over.