The speed of light is so fast that it's difficult to guess it's speed.
It's difficult to guess the speed of light because it's too fast.
英文翻译(中译英):光的传播速度如此之快以至于我们很难猜想它的速度
The speed of light is so fast that it's difficult to guess it's speed.
It's difficult to guess the speed of light because it's too fast.