One kilometer away1 公里外
The thunder comes almost right after the flash. The storm is very close.
閃光之後雷聲幾乎馬上就到。雷雨離你非常近。
Earth and Weather · Unit 2 · Lesson 9 · 地球與天氣 單元二 第九課
What Are Lightning and Thunder?閃電和打雷是怎麼回事？
A flash, a pause, and then a boom that shakes the windows. What is that light, what makes the noise, and why does the noise always come late? In a 3D model, watch a thundercloud fill with electric charge and let it go, then follow the sound as it travels to your house in real time. Last, learn to tell how far away a storm is by counting.
一道閃光，停了一下，然後是震得窗戶都在抖的一聲巨響。那道光是什麼？聲音是什麼東西發出來的？為什麼聲音總是比較晚到？在 3D 模型裡，看一朵雷雨雲怎麼充滿電、又怎麼把電放掉，再跟著聲音，看它用真實的速度傳到你家。最後，學會用數數的方法，知道雷雨離你多遠。
Big idea · 一句話看懂
Lightning is a giant electric spark. Inside a thundercloud, fast winds pull electric charge apart, with one kind at the top of the cloud and the other kind at the bottom. When the pull between them becomes too strong for the air to hold back, the charge jumps. The spark heats the air so suddenly that the air bursts outward, and that is thunder. Light reaches you at once, but sound is much slower, so the thunder comes later.
閃電是一個巨大的電火花。在雷雨雲裡，強勁的氣流把電分開：一種電在雲頂，另一種電在雲底。當它們之間的拉力大到空氣再也擋不住的時候，電就跳過去了。這個火花把空氣一下子加熱，空氣猛然向外爆開，這就是雷。光立刻就到你眼前，聲音卻慢得多，所以雷聲比較晚到。
3D Model · 3D 模型
Flash First, Boom Later 先閃電，後打雷
Drag to turn the model, and scroll or pinch to zoom. Watch the red and blue dots collect in the cloud as the charge builds. When the bar is full, lightning jumps. A yellow ring then spreads out along the ground. That ring is the sound, and it moves at its real speed. Slide the house closer or farther, and count the seconds until the ring reaches it.
拖曳可以旋轉模型，滾輪或雙指可以縮放。電越積越多的時候，注意看紅色和藍色的小點怎麼在雲裡聚集。長條滿了，閃電就放電。接著有一個黃色的圈沿著地面往外擴，這個圈就是聲音，它是用真實的速度在跑。把房子移近或移遠，數一數這個圈要幾秒才會到。
Drag to turn · 拖曳旋轉 Scroll or pinch to zoom · 滾輪／雙指縮放
This 3D model needs WebGL, which this browser does not support. The reading and the cards below still explain everything.
這個瀏覽器不支援 WebGL，無法顯示 3D 模型；下方的課文與卡片一樣能看懂。
- Red dots: positive charge
紅色小點：正電 - Blue dots: negative charge
藍色小點：負電 - Bright line: lightning
明亮的線：閃電 - Yellow ring: the sound of the thunder, spreading out
黃色的圈：往外擴散的雷聲
A teaching model. The ring of sound moves at its real speed, about 340 meters a second, and the distances along the ground are drawn to scale, so the seconds you count are true. The cloud is not to scale: a real thundercloud can be more than 6 kilometers tall. The few seconds it takes the cloud to charge were chosen for the animation, and real lightning is far quicker than the flash shown here. A real cloud holds countless charges, not sixteen dots.
這是教學用的模型。聲音的圈是用真實的速度（每秒大約 340 公尺）在跑，地面上的距離也照比例畫，所以你數到的秒數是真的。雲沒有照比例畫：真的雷雨雲可以高過 6 公里。雲充電的那幾秒是為了動畫設定的，真的閃電也比這裡畫的快得多。真的雲裡有數不清的電荷，不是十六個小點。
Model drawn by My Culture Connect as a teaching diagram. The ideas follow the Central Weather Administration's page on thunderstorms and the other sources listed at the bottom of this page. · 模型由人師教育協會自繪示意；原理依中央氣象署 氣象常識「雷雨」與本頁最下方列出的其他出處。
Reading · 英文閱讀
9
Unit 9: What Are Lightning and Thunder?
On a hot summer afternoon, the sky can change very quickly. A white cloud grows tall and turns dark at the bottom. Then there is a flash, and a few seconds later, a boom. For thousands of years people wondered what was happening up there. Today we know that it is electricity.
炎熱的夏天午後，天空可以變得很快。一朵白雲越長越高，底部漸漸變黑。接著是一道閃光，幾秒鐘之後，轟的一聲。幾千年來，人們一直在想：天上到底發生了什麼事？今天我們知道，那是電。
A thundercloud is a very busy place. Warm, moist air shoots upward, and cold air and rain fall back down. Inside the cloud, drops of water and bits of ice are thrown around and rub against each other. This pulls electric charge apart. Scientists still do not understand every detail, but the result is clear: positive charge collects near the top of the cloud, and negative charge collects near the bottom.
雷雨雲裡面非常熱鬧。暖溼的空氣往上衝，冷空氣和雨水往下掉。雲裡的水滴和冰粒被拋來拋去、互相摩擦，把電分開了。科學家到現在還沒有弄清楚每一個細節，但結果很清楚：正電聚在雲頂附近，負電聚在雲底附近。
Opposite charges pull on each other. The negative charge at the bottom of the cloud also pulls positive charge toward the ground just below. But air stands between them, and air does not let electricity pass easily. So the charge builds and builds. In some large storms, the push behind it reaches several million volts.
不同的電會互相吸引。雲底的負電，也把地面上的正電吸引到它的正下方。可是它們中間隔著空氣，而空氣不容易讓電通過。所以電就越積越多。在一些大雷雨裡，推動它的電壓可以高達幾百萬伏特。
At last the air cannot hold it back, and the charge jumps. That giant spark is lightning. It can jump inside one cloud, from one cloud to another, or between the cloud and the ground. All over the world, lightning strikes the ground about 100 times every second.
最後，空氣擋不住了，電就跳了過去。這個巨大的電火花就是閃電。它可以在一朵雲裡面跳，可以從一朵雲跳到另一朵雲，也可以在雲和地面之間跳。全世界加起來，閃電平均每秒鐘擊中地面大約 100 次。
Lightning is extremely hot. It heats the air around it to about 30,000 degrees Celsius in an instant. The air swells so fast that it bursts outward, like a small explosion. The sound of that burst is thunder. So thunder is not clouds crashing together. It is the sound of air being heated by lightning.
閃電非常燙。它在一瞬間把周圍的空氣加熱到大約攝氏三萬度。空氣膨脹得太快，猛然向外爆開，就像一場小小的爆炸。這個爆開的聲音就是雷。所以雷聲不是雲撞在一起的聲音，而是空氣被閃電加熱所發出的聲音。
Lightning and thunder happen at the same moment, but they do not reach you together. Light travels about 300,000 kilometers a second, so you see the flash at once. Sound travels only about 340 meters a second. If you count the seconds between the flash and the boom, you can tell how far away the lightning was. Every 3 seconds is about 1 kilometer.
閃電和雷聲是同時發生的，卻不會一起到你這裡。光每秒大約走 30 萬公里，所以閃光你立刻就看到了。聲音每秒只走大約 340 公尺。數一數從閃光到雷聲隔了幾秒，就可以知道閃電離你多遠：每 3 秒大約是 1 公里。
Read aloud · 課文朗讀
Questions · 閱讀理解
What happens to the electric charge inside a thundercloud?
It is pulled apart. Positive charge collects near the top of the cloud, and negative charge collects near the bottom, until the air cannot hold it back and it jumps.
What makes the sound of thunder?
Lightning heats the air around it so suddenly that the air bursts outward. The sound of that burst is thunder.
Why do you see the lightning before you hear the thunder?
Light travels about 300,000 kilometers a second, so it arrives at once. Sound travels only about 340 meters a second, so it arrives later.
Words & Phrases · 生字及片語
lightning(n.)閃電Lightning lit up the whole sky.閃電照亮了整片天空。thunder(n.)雷；雷聲We heard thunder far away.我們聽到遠處有雷聲。electricity(n.)電Lightning is a kind of electricity.閃電是一種電。charge(n.)電荷The cloud is full of electric charge.這朵雲裡充滿了電荷。flash(n.)閃光There was a bright flash outside the window.窗外有一道明亮的閃光。spark(n.)火花A small spark jumped from my finger.一個小火花從我的手指跳出來。sound(n.)聲音Sound is much slower than light.聲音比光慢得多。strike(v.)擊中；打中Lightning can strike a tall tree.閃電可能擊中高大的樹。
Quick Check · 小測驗
1. What is lightning?
2. What makes thunder?
3. Why does thunder come after the flash?
4. You count 6 seconds between the flash and the thunder. About how far away was the lightning?
5. Where should you NOT stand in a thunderstorm?
Be Ready · 防災要點
How far away was that lightning? 這道閃電離我多遠？
When you see a flash, start counting seconds: one thousand one, one thousand two… Stop when you hear the thunder. Set the slider to your number. Or press Test me: the box will flash, and the boom will come a few seconds later.
看到閃光就開始數秒：一秒、兩秒……聽到雷聲就停。把滑桿撥到你數到的數字。也可以按「考考我」：方塊會閃一下，過幾秒才會「轟」。
Press the button, then count. · 按下按鈕，然後開始數。
The distance is the number of seconds times 340 meters, the speed of sound given by the Central Weather Administration. Counting tells you how far away the last flash was. It does not tell you where the next one will strike, so it is not a way to decide that you are safe.距離＝秒數 × 340 公尺（中央氣象署採用的聲音速度）。數秒只能告訴你「剛才那一道」有多遠，不能告訴你下一道會打在哪裡，所以不能用它來判斷自己安不安全。
The lightning was about · 這道閃電大約在
1,020 meters away · 公尺外
That is about 1.0 kilometers. · 大約是這麼多公里。
A quick rule: every 3 seconds is about 1 kilometer. If the time between the flash and the thunder is getting shorter, the storm is coming closer.簡單的記法：每 3 秒大約是 1 公里。如果閃光和雷聲之間隔的時間越來越短，表示雷雨正在靠近。
Try It in the Model · 在模型裡試試
Four strikes 四道閃電
Press Strike now as many times as you like. No two bolts take the same path.
「現在就放電」可以一直按。每一道閃電走的路線都不一樣。
Three kilometers away3 公里外
Count slowly with the timer. The ring takes a while to cross the field.
跟著計時器慢慢數。那個圈要一陣子才會越過這片地。
Five kilometers away5 公里外
A long wait. In real life, the thunder would also sound softer and longer.
要等很久。在真實的情況裡，這時候的雷聲聽起來也會比較小、拖得比較長。
Inside the cloud在雲裡面
The spark jumps between the top and the bottom of the cloud and never touches the ground.
火花在雲頂和雲底之間跳，沒有碰到地面。
Go Further · 延伸閱讀
Where thunderclouds come from 雷雨雲是怎麼來的
Earth and Weather · Lesson 6 · 地球與天氣 第六課Why Does It Rain?為什麼會下雨？Rising air makes cloud. A thundercloud is what happens when the air rises very fast.空氣上升就會成雲。空氣升得非常快的時候，就長成雷雨雲。Go to the lesson · 前往這一課 →Earth and Weather · Lesson 8 · 地球與天氣 第八課How Does a Typhoon Form?颱風是怎麼形成的？Another storm that is powered by warm, moist air.另一種靠暖溼空氣提供能量的風暴。Go to the lesson · 前往這一課 →
Lightning by the Numbers · 閃電的數字
Six numbers about lightning 六個和閃電有關的數字
Very fast, very hot, and very common.
很快、很燙，而且很常見。
340 ma second · 每秒
The speed of sound in air. Thunder needs about 3 seconds to travel 1 kilometer.聲音在空氣裡的速度。雷聲走 1 公里大約要 3 秒。
300,000 kma second · 每秒
The speed of light. The flash of lightning reaches your eyes at once.光的速度。閃電的光立刻就到你的眼睛。
100a second · 每秒
Around the world, lightning strikes the ground about this many times every second.全世界加起來，閃電平均每秒鐘擊中地面大約這麼多次。
30,000°Chot · 高溫
Lightning heats the air around it to about this temperature in an instant.閃電在一瞬間把周圍的空氣加熱到大約這個溫度。
Millionsof volts · 伏特
In some large storms, the voltage between the cloud and the ground reaches several million volts.在一些大雷雨裡，雲和地面之間的電壓可以高達幾百萬伏特。
1–2hours · 小時
A single thundercloud does not last long. It usually grows, storms, and fades within one or two hours.單獨一朵雷雨雲的壽命很短，從發展、成熟到消散，通常不過一兩個小時。
Lightning Stories · 閃電的故事
The kite, the rod, the summer afternoon, and the giant trees 風箏、避雷針、夏天的午後，還有神木
How people came to understand lightning, and to live with it.
人們怎麼弄懂閃電，又怎麼和它相處。
1752
Is lightning electricity?閃電是電嗎？
Benjamin Franklin thought that lightning was the same thing as the small sparks people made in their experiments, only far bigger. He proposed a way to test it. In May 1752, a scientist in France tried Franklin's idea with a tall iron rod and drew sparks from a storm cloud. Lightning was electricity. Franklin is famous for flying a kite in a storm that same year. Nobody should ever copy that. It was extremely dangerous.
富蘭克林認為，閃電和人們在實驗裡做出來的小火花是同一種東西，只是大得多。他提出了一個檢驗的方法。1752 年 5 月，法國的一位科學家照他的想法，用一根很高的鐵棒從雷雨雲引出了電火花：閃電確實是電。富蘭克林最出名的故事，是同一年在雷雨中放風箏。千萬不要模仿，那是極度危險的事。
Buildings · 建築
How a lightning rod works避雷針是怎麼保護房子的
A lightning rod is a metal rod with its point facing up, fixed to the top of a tall building. A copper wire joins it to a copper plate buried in the ground. When a thundercloud comes near, charge gathers at the point of the rod and has an easy path to the earth. The electricity takes that path, not the path through the building.
避雷針是一根尖端朝上的金屬棒，裝在高大建築物的頂端，下面用銅線連到埋在地下的銅板。雷雨雲靠近的時候，電荷會集中在避雷針的尖端，並且有一條容易通到地下的路。電走的是這條路，而不是穿過建築物。
Taiwan · 台灣
Summer afternoons夏天的午後
In Taiwan, thunderstorms become more common from March and are most common in July and August. In summer they often come at about two or three in the afternoon, after the sun has heated the ground all morning. The rain cools the ground, the warm air stops rising, and the sky often clears again soon after.
在台灣，雷雨從 3 月開始變多，7、8 月最多。夏天的雷雨常常發生在下午兩三點，也就是太陽把地面曬了一整個上午之後。下過雨，地面涼了，熱空氣不再上升，所以短暫的雷雨過後，天氣常常很快又放晴。
Forests · 森林
Protecting the giant trees保護神木
Tall things that stand alone are the easiest targets, and in the mountains that often means very old, very tall trees. On April 7, 1973, lightning struck the cypress forest beside Xianglin Elementary School on Alishan and started a large fire. The Central Weather Administration suggests that the famous giant trees in forest parks should have lightning rods of their own.
孤立而高聳的東西最容易被雷打中；在山裡，那往往就是又老又高的大樹。民國 62 年（1973 年）4 月 7 日，雷擊中了阿里山香林國小旁邊的檜木林，引起一場大火。中央氣象署建議，森林風景區裡的神木，最好也幫它們裝上避雷針。
Myth vs. Fact · 常見迷思
Four things people get wrong 四個常見的誤會
✗ Myth · 迷思Thunder is the sound of clouds crashing together.雷聲是雲撞在一起的聲音。
✓ Fact · 事實Clouds are made of tiny drops and cannot crash. Thunder is air that lightning has heated, bursting outward.雲是很小的水滴，撞不出聲音。雷聲是被閃電加熱的空氣向外爆開的聲音。
✗ Myth · 迷思Thunder happens a few seconds after lightning.先閃電，過幾秒才打雷。
✓ Fact · 事實They happen at the same moment. The sound just takes longer to reach you.它們是同時發生的，只是聲音比較晚傳到你這裡。
✗ Myth · 迷思A big tree is a good place to wait out a thunderstorm.打雷下雨的時候，躲在大樹下最好。
✓ Fact · 事實It is one of the most dangerous places. Tall things that stand alone are the most likely to be struck.那是最危險的地方之一。孤立而突出的東西最容易被雷打中。
✗ Myth · 迷思Lightning always goes from a cloud down to the ground.閃電都是從雲打到地面。
✓ Fact · 事實It also jumps inside a cloud and from one cloud to another.它也會在一朵雲裡面跳，或是從一朵雲跳到另一朵雲。
Remember It · 記憶口訣
Lightning in a sentence 一句話記住閃電
Charge is pulled apart電被分開了
Positive on top, negative below.
正電在上，負電在下。
The spark jumps火花跳過去
That is lightning.
這就是閃電。
Hot air bursts熱空氣爆開
That is thunder.
這就是雷。
Count the seconds數一數幾秒
Three seconds, one kilometer.
三秒鐘，一公里。
Be Ready · 防災要點
In a thunderstorm 打雷的時候
- Check the forecast before you go running, hiking, or to the beach. The chance of being struck is high in the open during heavy rain.要去跑步、登山或到海邊之前，先看天氣預報。大雨中在空曠的戶外，被雷擊的機率相當高。
- Stay away from tall things that stand alone, such as towers, poles, chimneys, and big trees. Never shelter under a tree.不要靠近孤立而高聳的東西，例如鐵塔、電線桿、煙囪和大樹。千萬不要在樹下躲雨。
- Do not stand on open high ground.不要站在空曠的高地上。
- Do not swim or go out in a boat. A person or a boat on the water stands out and is easy to strike.不要游泳，也不要划船。水面上的人和船是很突出的目標，容易被擊中。
- Keep away from things that carry electricity well: wires, water pipes, and metal objects. Wet clothes and wet walls carry it too.遠離容易導電的東西：電線、自來水管和金屬器具。溼衣服和潮溼的牆壁也會導電。
These points follow the Central Weather Administration and the National Fire Agency: Central Weather Administration, Thunderstorms ↗以下要點依中央氣象署 氣象常識「雷雨」與內政部消防署消防防災館。
Classroom Activity 1 · 課堂活動一
Pull Charge Apart 把電分開
You need · 準備材料
- A balloon and a dry wool sweater or your own clean, dry hair一個氣球，還有一件乾的毛衣，或是你自己乾淨、乾燥的頭髮
- A sheet of paper torn into very small pieces一張撕成很小很小碎片的紙
Steps · 步驟
- Blow up the balloon and tie it. Hold it over the paper pieces. Does anything happen?把氣球吹起來、綁好。拿到碎紙片的上方：有什麼事發生嗎？
- Rub the balloon on the sweater or on your hair about twenty times.把氣球在毛衣或頭髮上摩擦大約二十下。
- Hold the balloon just above the paper pieces again. What do they do now?再把氣球拿到碎紙片的正上方。這一次紙片怎麼了？
- Try to stick the balloon to a wall. How long does it stay?試著把氣球貼在牆上。它可以黏多久？
Rubbing pulled charge apart, just as the wild winds do inside a thundercloud. This works best on a dry day. On a humid day the charge leaks away quickly.
摩擦把電分開了，就像雷雨雲裡猛烈的氣流做的事一樣。天氣乾燥的時候效果最好；潮溼的日子，電很快就漏掉了。
Classroom Activity 2 · 課堂活動二
Is the Storm Coming or Going? 雷雨是在靠近，還是在離開？
You need · 準備材料
- A thunderstorm, and a safe place indoors一場雷雨，還有一個安全的室內
- Paper and a pen紙和筆
Steps · 步驟
- Stay indoors. When you see a flash, count the seconds until you hear the thunder.留在室內。看到閃光，就開始數秒，數到聽見雷聲為止。
- Write the number down. Divide it by 3 to get the distance in kilometers.把數字記下來。除以 3，就是大約幾公里。
- Do the same for five flashes.用同樣的方法記錄五次閃電。
- Look at your five numbers. Are they getting smaller or larger? Which way is the storm moving?看看這五個數字：是越來越小，還是越來越大？雷雨正往哪個方向移動？
Do this only from inside a building. Counting is for learning about the storm, not for deciding when to go out.
這個活動只能在建築物裡面做。數秒是用來了解雷雨的，不是用來決定什麼時候可以出門。
Sources · 資料出處
Facts and numbers on this page were checked against these sources (October 2026). · 本頁的事實與數字依下列資料查證（2026 年 10 月）。
- How a thundercloud grows; positive charge at the top and negative charge at the bottom, attracting positive charge on the ground; the cause is not yet fully understood; air acts as an insulator; several million volts in some large storms; lightning inside a cloud, between clouds, and between cloud and ground; about 100 strikes a second worldwide; the leader and the return stroke; hot air expands and explodes as thunder; sound about 340 m/s and light 300,000 km/s; a single thundercloud lasts only an hour or two雷雨雲的發展；正電荷在雲的上端、負電荷在下方並吸引地上的正電荷；成因迄今還不能完全明白；空氣是絕緣體；有些大雷雨中電壓可達幾百萬伏特；閃電發生在雲裡、兩雲之間、雲與地面之間；全世界平均每秒約 100 次；前導閃擊與迴擊；熾熱空氣膨脹爆炸就是雷；聲速約每秒 340 公尺、光速每秒 30 萬公里；單獨一塊雷雨雲通常不過一兩小時中央氣象署 氣象常識「雷雨」 ↗
- In Taiwan thunderstorms increase from March and peak in July and August; summer heat thunderstorms often come at 2–3 p.m.; how to avoid being struck; how a lightning rod works; the Alishan fire of April 7, 1973台灣雷雨每年自 3 月起增加，7、8 月最盛；夏季熱雷雨常發生在午後 2、3 點；避免雷擊的方法；避雷針的構造；民國 62 年 4 月 7 日阿里山雷擊引起的森林火災中央氣象署 氣象常識「雷雨」 ↗
- Air in a thundercloud can rise 600 meters a minute, and the cloud can reach 6,000 meters in about ten minutes; the cloud holds both ice crystals and water drops積雨雲內氣流上升速度每分鐘最高可達 600 公尺，十分鐘左右雲柱可伸展至 6,000 公尺；雲柱中含有冰晶與水滴中央氣象署 氣象常識「雲與天氣」 ↗
- The chance of being struck is high when running, hiking, or at the seaside in heavy rain; sheltering under a tree is dangerous大雨中跑步、登山或在海邊受雷擊的機率相當高；在室外待在樹下躲雨很危險內政部消防署 消防防災館「颱風來時注意事項」 ↗
- Lightning heats the air around it to about 30,000°C閃電把周圍的空氣加熱到大約攝氏三萬度Wikipedia, “Lightning” (citing the U.S. National Weather Service) ↗
- Franklin proposed an experiment to show that lightning is electricity; on May 10, 1752, Thomas-François Dalibard carried it out in France with an iron rod富蘭克林提出證明閃電是電的實驗；1752 年 5 月 10 日，達利巴爾在法國用鐵棒完成Wikipedia, “Benjamin Franklin” ↗