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I bet that the last time you went to the beach, the wind was blowing in off the water.
我敢打賭，你最后一次去海灘的時候，海風正從水面吹來。
Maybe it was just a pleasant breeze, maybe something a little stronger.
或許是令人愉快的微風，也或許是更強一點的風。
But it was definitely coming in off the water.
但是它的確來自于水面。
What's more, a breeze will be coming in off the water the next time you go to the beach.
更重要的是，你下次去海灘的時候微風又會徐徐吹來。
How do I know? Easy.
我為什么會知道？那太容易了。
Wind is caused by differences in the temperature of air.
風是由空氣的溫差引起的。
If you have a lot of hot air in one location and a lot of cold air next to it, the line where they meet will be windy.
如果一個地方有大量的熱空氣，它的旁邊又有大量的冷空氣，那么冷熱空氣相交的地方就會形成風。
That's because the hot air is rising and the cold air is rushing in to fill the space left behind. Whoosh!
因為熱空氣上升，冷空氣就會迅速沖到熱空氣留下的位置里并填滿整個空間。
Now, here we are at the beach.
現在我們站在海灘上。
What do you notice?
你注意到了什么？
Well, the sand under your feet retains heat pretty effectively. Once it is hot, it stays hot.
你腳下的沙子能夠有效的保持熱量。一旦它變熱了，它就會維持熱度。
Not so for ocean water, which is much harder to heat.
可是海水卻很難變熱。
Think of how cold the water feels when you step into it off a hot beach.
想想當你從水中踏入炙熱的沙灘時，會發現海水是多么的寒冷啊！
This distinction is true of land and sea in general.
總的來說，這就是陸地和海洋的真實區別。
On a sunny day, the land stays hotter than the sea.
陽光明媚的日子，陸地比海洋要熱很多。
That means the air over the beach will be hotter than the air over the water.
那意味著海灘上空的空氣將會比水面上空的空氣熱。
And that means the air will be rising over the beach.
也就是說海灘上的熱氣將會上升。
As the hot beach air rises up, the relatively cooler air over the water moves in to take its place.
隨著海灘上空熱空氣的上升，水面上相對寒冷的空氣就會流動過來代替熱空氣的位置。
The result? A sunny day in summer creates its own breeze.
結果是什么呢？在夏天一個陽光燦爛的日子里有微風吹過。
