一年中日出最早的那天不是夏至

The earliest sunrise of the year isn't on the summer solstice

一年中日出最早的那天不是夏至

The summer solstice, which falls on June 21 in the Northern Hemisphere, offers more total sunlight than any other day of the year. It would seem to make sense, then, for the summer solstice to also feature the year's earliest sunrise and latest sunset.

6月21日是北半球的夏至，这一天的日照总量超过了一年中的任何一天。因此，夏至也有可能是一年中日出最早和日落最晚的一天。

Many people are surprised, however, to learn that isn't quite how it works. While the solstice offers the greatest amount of daylight overall, the earliest sunrise occurs before the solstice and the latest sunset falls afterward. The exact dates vary by latitude, with the year's earliest sunrise and latest sunset occurring further from the solstice date the closer you are to the equator.

然而，许多人惊讶地发现，事实并非如此。虽然夏至提供了最多的日照，但最早的日出出现在夏至之前，最晚的日落在夏至之后。确切的日期因纬度而异，离赤道越近，一年中最早的日出和最晚的日落发生的时间就离夏至日越远。

In Hawaii, for example, the earliest sunset is about two weeks before the summer solstice, and the latest sunset comes about two weeks after, as astronomy writer Bruce McClure explains for EarthSky. At the Northern Hemisphere's mid-northern latitudes, on the other hand, the earliest sunrise will take place June 14 and the latest sunset will follow on June 27.

例如，在夏威夷，最早的日落发生在夏至前两周，而最晚的日落发生在夏至后两周，天文学作家布鲁斯·麦克卢尔在接受EarthSky采访时解释道。另一方面，在北半球的中纬度地区，最早的日出将在6月14日，最晚的日落将在6月27日。

If you're in the Southern Hemisphere, the June solstice is the shortest day of the year. A city at 40 degrees north latitude (like Philadelphia) will see its earliest sunrise at 5:31 a.m. on June 14, for instance, while a city at 40 degrees south latitude (like Valdivia, Chile) will see its latest sunrise at 8:12 a.m. on the same day.

如果你在南半球，6月至日是一年中白昼最短的一天。比如，北纬40度的城市(像费城)日出时间最早，是6月14日凌晨5点31分，而南纬40度的城市(比如智利瓦尔迪维亚)日出时间最晚，是当天早上8点12分。

This is largely due to the tilt of Earth's rotational axis, as astronomer Ken Croswell explains in StarDate magazine, but it's also influenced by our elliptical orbit around the sun, which causes Earth to travel at different speeds throughout the year.

正如天文学家肯·克罗斯威尔在《StarDate》杂志上解释的那样，这在很大程度上是由于地球旋转轴的倾斜，但它也受到我们围绕太阳的椭圆轨道的影响，这导致地球全年以不同的速度运行。

For a more in-depth explanation, see this breakdown of the phenomenon from the U.S. Naval Observatory (USNO). And to find out when the sun will rise and set where you are, check out this calculator from the USNO's Astronomical Applications Department.

要了解更深入的解释，请参见美国海军天文台(USNO)对这一现象的分析。如果想知道你所在的地方，太阳什么时候会升起，什么时候会落下，请查看美国国家天文台天文应用部的数据。