Earth and Sky;September Equinox 秋分

September Equinox 秋分

We have an equinox because an imaginary plane extending outward from Earth's equator isn't the same as the plane of Earth's orbit around the sun. Learn more about today's equinox -- on Earth and Sky..

JB: This is Earth and Sky -- Sunday, September 22. No national or cosmic law says the equinox should mark the start of a new season.

DB: And yet we've come to regard solstices and equinoxes as the beginnings of seasons. We pin them down to the minute as Earth moves around the sun. During the night tonight according to U.S. clocks, the sun will cross the celestial¹ equator moving from north to south . . .

JB: And this equinox will be regarded as the beginning of autumn in the northern hemisphere -- and the start of spring in the southern hemisphere. Most people think of the equinox as a day -- but it's really just an instant -- when the sun crosses the celestial equator. That instant comes this evening for you if you're using Central, Mountain or Pacific Time in the U.S. -- or if you're in Hawaii. But it'll be after midnight on your clock tonight if you're in the Eastern time zone of the U.S. or in Europe or Africa.

DB: Signs of the equinox can be seen at any earthly latitude². Due east and due west are horizon markers in the equatorial system -- and since the sun is crossing the plane of Earth's equator tonight, the sun will rise due east and set due west tomorrow. Also, today or tomorrow, watch your shadow. At dawn, it'll point precisely³ west. At dusk, it'll point precisely east. Happy equinox everyone.

JB: And thanks today to Research Corporation -- a foundation for the advancement⁴ of science. We're Block and Byrd for Earth and Sky.

1 celestial   

adj.天体的；天上的

参考例句：

• The rosy light yet beamed like a celestial dawn.玫瑰色的红光依然象天上的朝霞一样绚丽。
• Gravity governs the motions of celestial bodies.万有引力控制着天体的运动。

2 latitude   

n.纬度，行动或言论的自由(范围)，(pl.)地区

参考例句：

• The latitude of the island is 20 degrees south.该岛的纬度是南纬20度。
• The two cities are at approximately the same latitude.这两个城市差不多位于同一纬度上。

3 precisely   

adv.恰好，正好，精确地，细致地

参考例句：

• It's precisely that sort of slick sales-talk that I mistrust.我不相信的正是那种油腔滑调的推销宣传。
• The man adjusted very precisely.那个人调得很准。

4 advancement   

n.前进，促进，提升

参考例句：

• His new contribution to the advancement of physiology was well appreciated.他对生理学发展的新贡献获得高度赞赏。
• The aim of a university should be the advancement of learning.大学的目标应是促进学术。