A solar eclipse happens when a new moon moves between the earth and the sun, blocking some or all of the sun's rays from reaching the earth. By cosmic chance, even though the sun is 400 times wider than the moon, it's also 400 times farther away. Therefore, the two objects appear the same size in our sky.
日蝕在新月移動到地球與太陽之間時發生，阻擋部分或所有陽光照到地球。宇宙中的小巧合，儘管太陽的寬度是月球的四百倍，它的距離也遠上四百倍。因此，這兩樣物體在我們的天空中看起來是一樣的大小。
Astronomers are able to predict eclipses because the earth and moon have very predictable orbits. Why, then, isn't there an eclipse every month? The moon's orbit is usually tilted a few degrees north or south in relation to the earth. When the moon does eclipse the sun, it casts two types of shadows on Earth: a smaller, darker shadow known as the "umbra" and a larger shadow known as the "penumbra."
因為地球與月球的軌道十分固定，天文學家得以預測日蝕現象。那麼，為什麼不會每個月都出現一次日蝕呢？月球繞地球的軌道通常會向北或向南傾斜幾度。當月球確實掩蓋太陽時，那會在地球投下兩種陰影：一種較小、較暗，被稱作「本影」的陰影，還有一種較為龐大，被稱作「半影」的陰影。
There are four types of solar eclipses. The first and the most spectacular is a total eclipse, when the moon completely covers the sun's surface. A total eclipse can only be seen if you're standing within the umbral shadow. That's why the imaginary line created by this shadow as it races across Earth is known as the "path of totality."
日蝕分為四種。第一種且最為壯觀的是日全蝕，發生在月球完全覆蓋太陽表面之際。日全蝕只有在你站在本影中時才能看見。那就是為什麼這種陰影劃過地球時產生的那條虛構的線被稱作「全蝕帶」。
People within the penumbral shadow see only a partial eclipse, the second type. From this view, outside the path of totality, the moon passes in front of the sun off center, never fully covering its surface.
位在半影中的人們只能看到日偏蝕，也就是日蝕的第二種。從這個視野觀看，位在全蝕帶以外，月球會從太陽中心附近前經過，永遠不會完全遮蓋太陽表面。
Third, an annular eclipse occurs when the moon passes directly in front of the sun. However, unlike a total eclipse, the moon appears too small to fully cover the sun. The moon's orbit is elliptical, so sometimes it's closer to Earth, and sometimes it's farther away.
第三種，日環蝕在月球直接從太陽前經過時發生。不過，和日全蝕不同，月球看起來會太小，無法完全蓋住太陽。月球的軌道是橢圓形的，所以有時它會靠地球近些，而有時它又會離比較遠。
Last, a hybrid eclipse is when the moon's position between the earth and sun is so finely balanced that the curvature of the earth plays a role. The moon will be farther away from some parts of Earth along the eclipse's path, resulting in an annular eclipse. In other parts, the moon will be just close enough to fully cover the sun, resulting in a total eclipse.
最後一種，全環蝕發生的時機是月球在地球與太陽間的位置精準平衡，使得地球曲率在其中發揮影響。在日蝕路徑上，月球會離地球的某些地區較遠，造成日環蝕出現。在其它地區，月球的距離則剛好近到能完全擋住太陽，造成日全蝕出現。
While a total solar eclipse happens somewhere on Earth every year or two, any given point on Earth experiences the event only about once every 400 years.
雖然日全蝕每一兩年就會在地球某處出現，但地球上任何一個地方大概每四百年才會看到一次日全蝕。
We interrupt this video for an important safety announcement.
插播一則重要安全宣導。
Looking directly at the sun, even during an eclipse, can cause permanent eye damage. Fortunately, there are ways to enjoy an eclipse safely. The easiest is to use certified eclipse-watching glasses, which are shaded thousands of times darker than typical sunglasses. You can also look at the eclipse indirectly by making a pinhole viewer. Simply poke a small hole in a piece of cardboard; hold the cardboard up to the sun, allowing the sun's image to be projected onto a flat surface. Be sure to look only at the surface and not through the cardboard.
直視太陽，即便在日蝕期間，都可能會造成眼睛永久損害。幸好，有一些能安全觀賞日蝕的方法。最簡單的一種是利用合格的日蝕觀測眼鏡，它的顏色比普通太陽眼鏡深數千倍。你也可以做一個針孔裝置來間接觀看日蝕。只要在紙板上戳一個小洞；將紙板舉高對著太陽，讓太陽的影像投射到一個平面上。務必只看投射表面，不要透過紙板看太陽。
Just before the moon completely covers the sun, low-lying valleys on the moon's edge will be the only spots that sunlight continues to pass through. These remaining brilliant shafts of light, known as Baily's beads, will disappear one after another. And finally, a single bead of light remains, known as the diamond ring, signaling that you're just seconds away from experiencing totality. Once the last bead disappears and the moon completely covers the sun's surface, the view through your eclipse glasses will be pitch-black. Totality achieved!
就在月球完全遮蓋太陽前，月球邊緣那些低矮的峽谷是陽光唯一繼續穿過的地方。這些餘留的明亮光束，它們被稱作「倍里珠」，將會相繼消失。最後，只剩下一個倍里珠，那被稱作「鑽石環」，這表示再過幾秒你就能體驗日全蝕了。一旦最後一個倍里珠消失，而月球完全遮掩住太陽表面，你從日蝕眼鏡中看到的景象就會變一片漆黑。日全蝕來了!
At this point, none of the sun's rays are reaching your eyes, and it's the only time that it's safe to take off your glasses. Remember to put your eclipse glasses back on before any of the sun's rays start to peek through again. Any sunlight reaching your eyes, even for a few seconds, can cause serious damage. While an eclipse can last a few hours, totality typically occurs for less than three minutes.
此時，沒有半點陽光照到你的眼睛，這是唯一能安全脫下眼鏡的時刻。記得要在任何陽光又開始露出前戴回你的日蝕眼鏡。讓任何陽光照到你的眼睛，即使只有幾秒都會造成嚴重傷害。雖然日蝕會持續好幾小時，但日全蝕通常不會出現超過三分鐘。
Animals and plants have also been known to alter their behavior during a total eclipse. Songbirds may stop singing, crickets may stop chirping, and flowers may even start to close up.
人們也發現動植物在日全蝕發生期間會改變行為。鳴禽可能會停止歌唱、蟋蟀可能會停止唧唧叫，花朵們甚至還可能開始閉合。
We won't always be able to see total solar eclipses. The moon moves about one and a half inches away from Earth each year. It's estimated that in about a billion years, the moon will be too far away from Earth to completely cover the sun.
我們不會一直都能觀賞到日全蝕。月球每年約遠離地球 1.5 英吋。據估計，大約十億年後，月球離地球的距離就會太遠，遠到無法完全遮蔽住太陽。
- 「關於、就...相較而言」- In Relation To
The moon's orbit is usually tilted a few degrees north or south in relation to the earth.
月球繞地球的軌道通常會向北或向南傾斜幾度。 - 「導致、引起」- Result In
In other parts, the moon will be just close enough to fully cover the sun, resulting in a total eclipse.
在其它地區，月球的距離則剛好近到能完全擋住太陽，造成日全蝕出現。 - 「一個接一個、接連」- One After Another
These remaining brilliant shafts of light, known as Baily's beads, will disappear one after another.
這些餘留的明亮光束，它們被稱作「倍里珠」，將會相繼消失。 - 「脫下、摘下」- Take Off
At this point, none of the sun's rays are reaching your eyes, and it's the only time that it's safe to take off your glasses.
此時，沒有半點陽光照到你的眼睛，這是唯一能安全脫下眼鏡的時刻。 - 「能夠」- Be Able To
We won't always be able to see total solar eclipses.
我們不會一直都能觀賞到日全蝕。
