为何用does而不是was

Question

So fast does light travel that we can hardly imagine its speed.

为什么是does 而不是was？
我总是搞不清does，was什么的，请给通俗化的讲解一下 谢谢。

多举些例子和讲解。！
哦差不多明白了。。
还有个问题， 关于feel pain 还是 feel painful = = 请详解和举例句..

Answer 1

was+形容词
dose+动词

这里光的旅行，travel是动词。

如果这里要用was(应该是is啦，又不存在过去式），句子应该为
So fast is the light's speed that we can hardly imagine. 速度是名词，就可以用was

Answer 2

travel是动词，问句用does
Light travel so fast that we can hardly imagine its speed.这样看更明了些。主语是light

painful 的实际意思是“使人感到疼痛的”、“使人感到痛苦的”，所以它通常只能用来说明事物，不宜用来说明人
Does it still feel painful? 它还疼吗？

要用形容词表示汉语的“感到疼痛的”，英语可用 pain
Did you feel any pain? 你感觉痛吗？

Answer 3

was是is的过去式，用在表示过去发生的动作的句子（一般过去时）中。does是助动词，do的单三形式，用于一般现在时。
She does her homework very well.
Does she do her homework very well?
She doesn't do her homework very well.