Sun

“	Then Anar arose in glory, and the first dawn of the Sun was like a great fire upon the towers of the Pelóri: the clouds of Middle-earth were kindled, and there was heard the sound of many waterfalls. Then indeed Morgoth was dismayed, and he descended into the uttermost depths of Angband, and withdrew his servants, sending forth great reek and dark cloud to hide his land from the light of the Daystar.	”
–Quenta Silmarillion: Of the Sun and Moon and the Hiding of Valinor

The sun is a sprite in Middle-earth that appears every day in the east and sets in the west. Most Men prefer to fight while the sun is high, while Orcs and other evil creatures usually wait until sunset before attacking. The sun in Minecraft and the Mod is always exactly opposite of the moon, which rules the night.

Mechanics

The sun causes every block in direct sight of the sky (in other words, there's no other block atop it) to assume a light level of 15, provided that the weather is clear, and the sun is high. If the weather is not clear, the light level will be reduced to 12 during rain, and 7 during a thunderstorm. At sunset, the light level slowly decreases. A light level of 7 or lower will cause evil NPCs to spawn in many biomes. Good NPCs generally spawn regardless of light level.

Differences from Vanilla

While the sun in Middle-earth is very similar to that of Minecraft Vanilla, there are a few important differences:

The first (and most obvious) difference is that Middle-earth's sun is round, whereas the Minecraft sun is square.
Secondly, it stays in the sky twice as long; a day/night cycle in Middle-earth lasts 40 minutes, where 20 minutes of that is daytime.
Finally, if the player looks directly at the sun when it's up, their screen will go white, making it very difficult to see for a few seconds. This sun flare can be disabled via the config file.

It is also worth mentioning that staying in the direct sunlight of Near Harad will cause you to take heat damage every few seconds. In order to prevent this, you must either travel at night or wear robes (added in Public Beta 24).

Sunlight also weakens and slows orcs and turns most Trolls to stone apart from some exceptions.

Gallery

Trivia

Anórien, a fiefdom of Gondor, is Sindarin for "Sunlending", or more literally the "Sun-lands".
The Anglo-Saxon Sigel-rune ᛋ (= letter S) means "sun". Tolkien used those ᚱᚢᚾᛖᛋ for some texts in the initial drafts of "The Lord of the Rings", later on, he replaced them by Cirth.

“	ᛋ The sun is ever a joy in the hopes of seafarers when they journey away over the fishes' bath, until the courser of the deep bears them to land.	”
–Old English rune poem