Sun

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.

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. A light level of 7 or lower will cause evil NPC's to spawn in many biomes. Good NPC's 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.

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 (and avoid the Desert Scorpions), wear Near Haradrim Armour, or Near Haradrim Robes (in Beta 24).