At its best, the Koran is soaring religious poetry.  At its worst, it can sound like the improvisations of a barbarous outlander out of touch with the civilized world.  People in the seventh century knew that the earth was round; Ptolemaic astronomy was premised on that fact. But it is far from obvious that Mohammed knew what they knew.

Miry Fount

Mohammed is under the impression the sun sets at a particular locale on the earth:

"...And a route he followed, until when he reached the setting of the sun, he found it to set in a miry fount; and hard by he found a people...Then followed he a route until when he reached the rising of the sun he found it to rise on a people to whom we had given no shelter from it." (Sura 18:83-89).

One can find similar references in the Iliad, where they seem to be manifest symptoms of flat-earthism:

"Now the sun of a new day struck on the ploughlands, rising out of the quiet water and the deep stream of the ocean to climb the sky." (Iliad, Book 7, 421-423);

"So he spoke, and Hera of the white arms gave him no answer. And now the shining light of the sun was dipped in the Ocean trailing black night across the grain-giving land." (Iliad, Book 8, 484-486);

"Now the lady Hera of the ox eyes drove the unwilling weariless sun god to sink in the depth of the Ocean, and the sun went down, and the brilliant Achaians gave over their strong fighting, and the doubtful collision of battle." (Iliad, Book 18, 239-242).

The concept that there is a particular locale upon the face of the earth which is the very place where the sun sets is difficult to reconcile with any other astronomy than flat-earth.

Like a Carpet

Further eroding confidence is Mohammed's penchant for employing similes for the earth like 'carpets' and 'beds' which don't spring to mind as the most natural analogy for a round earth: "And the Earth -- we have stretched it out like a carpet; and how smoothly have we spread it forth!" (Sura 51:48).  Only with a great many tucks, darts and safety pins is a 'carpet' fitted to a round planet.

"He hath spread the earth as a bed, and hath traced out paths for you therein, and hath sent down rain from Heaven, and by it we bring forth the kinds of various herbs..." (Sura 20:55).

"Who hath made the earth a bed for you, and the heaven a covering, and hath caused water to come down from heaven, and by it hath brought forth fruits for your sustenance!" (Sura 2:20).

"And God hath spread the earth for you like a carpet,
That ye may walk therein along spacious paths." (Sura 71:18-19).

Level Earth

Mohammed says the earth is 'level':

"It is He who hath made the earth level for you: traverse then its broad sides, and eat of what He hath provided. -- Unto Him shall be the resurrection." (Sura 67:15).

From what perspective is he speaking? Is he contrasting the traversable plains of Arabia to more inaccessible mountainous zones? Or is he describing the earth/sky system from the point of view of an outside observer?

Speaking of the end of days, he talks about the earth being "stretched out as a plain:"

"When the Heaven shall have split asunder and duteously obeyed its Lord; and when Earth shall have been stretched out as a plain, and shall have cast forth what was in her and become empty..." (Sura 84:1-4).

"And call to mind the day when we will cause the mountains to pass away, and thou shalt see the earth a levelled plain, and we will gather mankind together, and not leave of them any one." (Sura 18:45).

None can doubt that God can produce whatever changes He wishes in the earth/sky system. Again, from what perspective is Mohammed speaking? Is he contrasting the level plains with the mountains, or speaking as an outside observer?

Solid Heavens

As will be seen, Mohammed is prone to fretting about the sky falling.  He describes the heaven as 'solid', which would explain his concerns about pieces falling off: "And built above you seven solid heavens, And placed therein a burning lamp..." (Sura 78:12-13). Under this solid structure is a firm foundation:

"It is God who hath given you the earth as a sure foundation, and over it built up the Heaven, and formed you, and made your forms beautiful, and feedeth you with good things." (Sura 40:66).

The 'seven' heavens, familiar from the astronomical musings of the Talmudic Rabbis, correspond to the number of the then-known planets plus the sun and moon: "He it is who created for you all that is on Earth, then proceeded to the Heaven, and into seven Heavens did He fashion it: and He knoweth all things." (Sura 2:27).

"See ye not how God hath created the seven heavens one over the other? And He hath placed therein the moon as a light, and hath placed there the sun as a torch..." (Sura 71:14-15)

"And He made them seven heavens in two days, and in each heaven made known its office: And we furnished the lower heaven with lights and guardian angels." (Sura 41:11).

"And we have created over you seven heavens: -- and we are not careless of the creation." (Sura 23:17).

"SAY: Who is the Lord of the seven heavens, and the Lord of the glorious throne?" (Sura 23:88).

"The seven heavens praise him, and the earth, and all who are therein; neither is there aught which doth not celebrate his praise; but their utterances of praise ye understand not. He is kind, indulgent." (Sura 17:46).

He refers to heaven as a structure, a "roof:"

"And we made the heaven a roof strongly upholden; yet turn they away from its signs." (Sura 21:33).

What was the predominant scientific astronomy in Mohammed's day?:

Tent-Stakes

Mohammed seems stuck on the idea of the earth being...stuck, weighted down by all those mountains:

"Without pillars that can be seen hath He created the heavens, and on the earth hath thrown mountains lest it should move with you; and He hath scattered over it animals of every sort..." (Sura 31:9);

"And He hath thrown firm mountains on the earth, lest it move with you; and rivers and paths for your guidance..." (Sura 16:15).

"Have we not made the Earth a couch? And the mountains its tent-stakes?" (Sura 78:6-7).

"And we set mountains on the earth lest it should move with them, and we made on it broad passages between them as routes for their guidance..." (Sura 21:32).

Somebody better get a crow-bar and pry off all those mountains so it can orbit...

The Sky is Falling

Mohammed's fretting about the sky falling does not sound as if intended as irony. The Kaabah, the sacred structure about which Muslim pilgrims circumambulate, contains, it is said, a black stone which appears to be a meteorite. Evidently this stone had long been held in reverence; the Christian author Clement of Alexandria, writing in the early third century, mentions it: "In ancient times, then, the Scythians used to worship the dagger, the Arabians their sacred stone, the Persians their river." (Clement of Alexandria, Exhortation to the Greeks, Chapter III, p. 101 Loeb edition).

The Hadith

The recollections of Mohammed's contemporaries are employed in working up Muslim law, because the Koran's scattershot injunctions do not make up a complete law-code. The sects differ as to the authenticity of the material in the traditional collections. These 'hadith' also touch upon astronomy:

"Narrated Abu Dhar: 'The Prophet asked me at sunset, "Do you know where the sun goes (at the time of sunset)?" I replied, "Allah and His Apostle know better." He said, "It goes (i.e. travels) till it prostrates Itself underneath the Throne and takes the permission to rise again, and it is permitted and then (a time will come when) it will be about to prostrate itself but its prostration will not be accepted, and it will ask permission to go on its course but it will not be permitted, but it will be ordered to return whence it has come and so it will rise in the west. And that is the interpretation of the Statement of Allah: "And the sun Runs its fixed course For a term (decreed). that is The Decree of (Allah) The Exalted in Might, The All-Knowing."'" (Hadith, Sahih Bukhari, Volume 4, Book 54, Number 421.)

Prostration

"Have they not seen how everything which God hath created turneth its shadow right and left, prostrating itself before God in all abasement?" (Sura 16:50)

What Mohammed visualizes here is the daily procession of shadows cast by stationary objects as a 'prostration' or act of worship. This makes more sense if God is visualized, not as omnipresent, but as seated upon a throne at the zenith of the sky: "His Throne reacheth over the Heavens and the Earth, and the upholding of both burdeneth Him not; and He is the High, the Great!" (Sura 2:256). There is no verse in the Koran corresponding to John 4:24, "God is a Spirit."

"And unto God doth all in the Heavens and on the Earth bow down in worship, willingly or by constraint: their very shadows also morn and even!" (Sura 15:16).

Bed-Time

"A sign to them also is the Night. We withdraw the day from it, and lo! they are plunged in darkness; and the Sun hasteneth to her place of rest. This, the ordinance of the Mighty, the Knowing!" (Sura 36:37-38).

The idea that the sun, like an exhausted farmer, rests at night, may be poetic diction, an instance of Ruskin's 'pathetic fallacy.' Or it might be intended as a matter-of-fact description of the sun's daily routine. If the latter, it's a flat-earth reference, because in no other system is the sun doing, or not doing, anything different when her rays are not seen from one hemisphere.

Copernicus

The heliocentric Copernican system, upon its first publication, met with indignation, not only from the Roman Catholic church, but also from Martin Luther. A rotund earth was not a novelty of this system, the Ptolemaic system already had that. Copernicus' innovation still meets with indignation in some quarters today...such as Saudi Arabia: "When in 1966, for example, he [Sheikh Bin Baz] had condemned what he termed the Copernican 'heresy,' insisting, as the Koran said, that the sun moved, Egyptian journalists, much to President Nasser's delight, had mercilessly mocked the leading cleric as a reflection of Saudi primitiveness." (Judith Miller, God has Ninety-Nine Names, p. 114).

Comments about the sun moving include,

"And He it is who hath created the night and the day, and the sun and the moon, each moving swiftly in its sphere." (Sura 21:34).

"Seest thou not that God causeth the night to come in upon the day, and the day to come in upon the night? and that he hath subjected the sun and the moon to laws by which each speedeth along to an appointed goal? and that God therefore is acquainted with that which ye do?" (Sura 31:28).

"He causeth the night to enter in upon the day, and the day to enter in upon the night; and He hath given laws to the sun and to the moon, so that each journeyeth to its appointed goal: This is God your Lord: All power is His..." (Sura 35:14).

"To the Sun it is not given to overtake the Moon, nor doth the night outstrip the day; but each in its own sphere doth journey on." (Sura 36:40).

"For truth hath he created the Heavens and the Earth: It is of Him that the night returneth upon the day and that the day returneth upon the night: and He controlleth the sun and the moon so that each speedeth to an appointed goal. Is He not the Mighty, the Gracious?" (Sura 39:7).

To an earth-bound observer the sun does apparently move. Such language might be phenomenological, describing what an observer within the system sees. It might also intend to describe what a privileged observer standing outside the system would see. In the Ptolemaic system of astronomy, such an observer would see the sun move:

A moving sun is of course also consistent with flat-earth astronomy.

"It is God who hath reared the Heavens without pillars thou canst behold; then mounted his throne, and imposed laws on the sun and moon: each travelleth to its appointed goal." (Sura 13:2).

Calendrical Reform

Mohammed legislated a calendrical reform for his people, or rather a calendrical anti-reform or retrogression. Because twelve lunar months add up to less than one solar year, the pagan Arabs used to intercalate an extra month as required. Mohammed would have none of that:

"Twelve months is the number of months with God, according to God's book, since the day when He created the Heaven and the Earth: of these four are sacred: this is the right usage: But wrong not yourselves therein; attack those who join gods with God in all, as they attack you in all: and know that God is with those who fear Him. To carry over a sacred month to another, is only a growth of infidelity. The Infidels are led into error by it. They allow it one year, and forbid it another, that they may make good the number of months which God hath hallowed, and they allow that which God hath prohibited. The evil of their deeds hath been prepared for them by Satan: for God guideth not the people who do not believe." (Sura 9:36-37)

This is progress in a rear-ward direction. It really is a good idea to intercalate an extra month into a lunar calendar, because twelve lunar months do not add up to 365-1/4 days. They used to do that, in the times of ignorance:

"The intercalators are those who used to adjust the months for the Arabs in the time of ignorance. They would make one of the holy months profane, and make one of the profane months holy to balance the calendar. It was about this that God sent down: 'Postponement (of a sacred month) is but added infidelity by which those who disbelieve are misled.' [Sura 9:37]" (Life of Muhammad by Ibn Ishaq, translated by A. Guillaume, pp.21-22).

In their "times of ignorance" they were wiser than they would later be, because in the uncontrolled lunar calendar now used by Muslims, months gyrate wildly through the seasons.

Conclusion

Not only a geocentrist, Mohammed, if we adopt the simplest and most plausible explanation for the Miry Fount, was a flat-earther, an idea retrograde even for his own time.

Some people take a 'so's your old man' approach to Christian criticism on this point, claiming that the Bible also teaches a flat earth. Does it really?: