The ionosphere is a high part of Earth’s air, far above the weather, where the sun’s energy has turned many of the gas particles into ions. Because those charged particles are there, this layer can bounce certain radio waves back down to Earth.

The ionosphere is電離層是 a high part of Earth's air地球大氣層裡很高的一部分, far above the weather遠在天氣現象之上, where太陽的能量在那裡 the sun's energy has turned many of the gas particles into ions把很多氣體粒子變成了離子. Because因為 those charged particles are there那些帶電粒子存在那裡, this layer can bounce certain radio waves back down to Earth這一層可以把某些無線電波反彈回地球。

That is how, before satellites, people sent radio signals around the curve of the world: the wave went up, hit the ionosphere, and came down far away.

That is how這就是為什麼, before satellites在衛星出現以前, people sent radio signals around the curve of the world人們能把無線電訊號傳過地球的弧面: the wave went up訊號往上走, hit the ionosphere碰到電離層, and came down far away然後在很遠的地方落下。

It is not one thin sheet. It is a thick region, starting tens of kilometres up and stretching much higher, and it changes from day to night and from season to season — which is why a far-off radio station can be clear one evening and full of noise the next.

It is not它不是 one thin sheet一層薄薄的東西. It is它是 a thick region一個很厚的區域, starting tens of kilometres up從幾十公里高的地方開始 and stretching much higher並向上延伸得更高, and it changes from day to night and from season to season而且會隨著日夜和季節改變 — which is why這就是為什麼 a far-off radio station can be clear one evening and full of noise the next一個遠方的電台可能今晚清楚、隔天卻滿是雜訊。