日出[Sunrise] - 达人(其实～我是卧底，来自外星)

2005/11/02 | 日出[Sunrise]
类别(¤〖天文〗) | 评论(0) | 阅读(15) | 发表于 21:38: Sunrise is the time at which the leading limb of the Sun first rises above the horizon. The effect of refraction in the Earth's atmosphere lifts the image of the Sun about half a degree at the horizon, making sunrise about two minutes earlier than would be expected from the actual position of the Sun in space. Refraction and the fact that sunrise and sunset are calculated from the limb (and not the center) slightly lengthen "day" relative to "night."

The above plot shows the time of sunrise from Chicago in U.S. Central Standard Time, so actual times must be shifted to account for daylight saving time. In 1999, the earliest and latest sunrises occur on June 14 at 5:23 CST and January 4-5 at 8:15 CST, respectively.; 0