The Gemara says (נדרים לט:): that in the time of the machlokes of Korach, the sun and the moon went away from their place in the heaven called רקיע, going higher up to the heaven called זבול, saying that they do not want to shine on the world. The sun and moon told Hashem that if He will stick up for Moshe Rabbeinu, they will shine onto the world. However, if He will not do so, they refused to. The Gemara continues that, in reaction, Hashem said that "Every day there are people who bow to you instead of to Me." However, they still keep shining daily and do not protest His honor. Why only now are they protesting? Then Hashem shot arrows at them, forcing them to continue with their mission on this world. The Gemara says that since then Hashem shoots arrows at the sun every day, thus he is forced to shine down on the world.
Why indeed was it the sun and the moon who so profusely protested Moshe Rabbeinu's kavod here?
We know that at the time of the world's creation, the moon protested that there can't be two great illuminators, the sun and him. In response, Hashem told the moon "Go and minimize yourself." לכי ומעטי את עצמך With this retort, Hashem established an important concept in creation. The concept that always the smaller, the lesser, must accept and learn from the greater. That's the way of the world.
The Chasham Sofer explains that initially the moon was not even created to shine with the same strength as the sun. The sun was to shine during the day when complete light is necessary, and during the night, when the moon was to shine, such a light is not needed nor wanted. Hence, he was not created to shine as much as the sun.
What changed after the moon protested? Now the moon would not have its own power, he would not have his own light, but rather he will reflect the light of the sun onto the world. (חתם סופר בראשית ד"ה את שני המאורות)