Genesis 1:16

1 the two great luminaries: They were created equal, but the moon was made smaller because it brought charges and said, “It is impossible for two kings to use the same crown.” - [from Chullin 60b] Rashi (ad loc.) explains that this derash is based on the discrepancy of the two expressions, “the two great luminaries,” which intimates that the moon was a great luminary, and“the lesser luminary,” which intimates that the moon was smaller than the sun. To reconcile this difference, the Rabbis asserted that the moon was originally created equal to the sun, but, because of its complaint that the sun wielded the same power that it wielded, it was forced to relinquish that power.

2 and the stars: Because He diminished the moon, He increased its hosts, to appease it. - [from Gen. Rabbah 46:4 and Chullin 60b] i.e., The stars serve as the entourage of the moon. When it comes out, they accompany it, and when it sets, they too set. [Gen. Rabbah ad loc.]

And the Lord made two great luminaries; and they were equal in glory twenty and one years, less six hundred and two and seventy parts of an hour. And afterwards the moon recited against the sun a false report; and she was diminished, and the sun was appointed to be the greater light to rule the day; and the moon to be the inferior light to rule in the night, and the stars.

And He made - the two were called "great" as compared to the stars. Similarly, the three [oldest] sons of Yishai were called "great/oldest" as compared to the others, while Eliav was the first-born, the oldest of all of them. It does not mean [here] that one was greater than the other, for there is a hidden meaning - the dominion of the sun in the day and not at night, for it has no light [then]. And likewise regarding the moon and starts, their light is not seen in the day. Now if one should ask, behold the astronomers have said that Jupiter and all the planets except for Mercury and Venus are larger than the moon, so how can it write "the great ones" [including the moon]? The answer is that "the great ones" does not refer to their physical measure, but rather to their light, and the light of the moon is many times greater, due to its being close to the earth, and therefore is it written "luminary".

AND G-D MADE. 17. AND G-D SET THEM. This teaches us that these lights were not made from the body of the firmament, rather, they were bodies set into it.

הקטן, the smaller of the two.

ויעש...ויתן...להאיר...ולמשול..ולהבדיל..כי טוב, all of these expressions refer to the luminaries and the other stars. The Torah first writes: ויעש, seeing that up until that point sun and moon had simply been part of all the other celestial bodies which had been created on the second day, or of “heaven,” whose creation had already been reported in verse 1. This is the reason why at this stage the Torah does not call the development of these luminaries an act of creation, ויברא or something similar, but merely writes ויעש, which describes the completion of a process that had already been begun previously. At this stage, G’d singled out these two luminaries from among all the planets and assigned them their function

The word כי טוב, “that it was good,” describes G’d’s impression after He had removed these luminaries from their original place in the universe, given them spherical shape so that they can orbit, and function as luminaries.

ויעש, “He completed making;” now the Torah reports how G’d arranged that the luminaries give their light onto the surface of the earth. Each luminary had a certain period assigned to it during which it would function.

הגדולים, the Torah did not write גדולים which would have described their physical size, seeing that all the planets with the possible exception of נגה, Venus, are larger than the moon. According to our astronomers they are further removed from earth, and this is why they appear to be smaller. The Torah speaks of the relative strength of the light provided by sun and moon respectively. The reason that both luminaries are referred to as הגדולים, is simply because they both appear larger than the fixed stars. Of these two, however, the sun is larger than the moon, as pointed out when the Torah says that the larger one is to shine by day. This also appears to us to be the case when we look at these two luminaries. According to the astronomers the sun is 170 times the size of the moon. The moon, being basically black, does not produce any light of its own but merely reflects the light of the sun, as a mirror reflects light. This accounts for the fact that its light varies in intensity depending on the day of the month, and on its position vis-à-vis the sun on such a day. The Torah therefore describes it as המאור הקטן, the small luminary.

ואת הכוכבים, for they too function at night, providing some light both when the moon is shining and when it is not on the horizon. The sun, on the other hand, does not shine at all during the night, seeing it is beneath the earth at that time. [the earth being perceived as flat at that time. Ed.] The moon and stars do not shine by day as the light of the sun, which is so much stronger, outshines them. When the Torah speaks of ממשלה in connection with these luminaries, it refers to the commanding influence the light of these luminaries have during the periods when they are functioning as providers of light.

“the two large luminaries.” They were both large, when compared to the appearance of the stars, though one of the two was considerable larger than its counterpart. According to our sages in the Talmud, they had originally been created equal in size, but as a result of the moon complaining about its having to share equally in illuminating the earth, G–d decreed for it to be diminished in size. (Talmud, tractate Chulin folio 60) The sun was allowed to retain its original size as it had listened in silence to the moon’s complaint which had implied that it felt superior to the sun. It is this incident which prompted the sages in Yalkut Shimon Judges, 5,59 to apply to such humble creatures the verse in Judges 5,31: ואוהביו כשמש כצאת בגבורתו, “but may His friends be as the sun rising in might.” According to that interpretation the sun had been made bigger as a reward for its humility whereas the moon had retained its original size. Alternately, while not having been enlarged physically, the sun had grown in stature due to its humility. According to a segment in our Shabbat morning prayers, i.e. keyl adon, the moon had been reduced in size, i.e. ראה והקטין צורת הלבנה, “He saw and reduced the dimensions of the moon.” [The version of this line in our prayer books has the word: והתקין “He adjusted,” instead of והקטין, He diminished. Ed.] According to another interpretation, the “correction” in the two descriptions of the luminaries in the Torah in the same verse even, was due to G–d having foreseen that the gentiles were apt to treat the sun as a major deity, He therefore tampered with the size and function of the moon in order to teach mankind that neither luminary was a deity.