Welcome to episode 2 of Crash Course Astronomy: Naked Eye Observations.

肉眼观察。

Yet, imperceptible to the human eye.

然而肉眼却无法看见它。

Four were visible to the unaided eye.

其中四颗肉眼可见。

Most stars are not visible to the naked eye.

大多数星星肉眼看不见。

And it may be visible, it may not be.

可能肉眼可见，又可能不可见。

The human eye can distinguish one thousand different shades of color.

肉眼能分辨出一种不同色调。

By eye, it might be difficult to appreciate how good a fit it is.

肉眼可能很难看出曲线多么吻合。

His brush stroke so subtle as to be invisible to the naked eye.

他笔触非常微妙，肉眼看不见。

The Great Wall is not visible with the naked eye from space.

长城在太空中用肉眼是看不。

Germs are not visible to the naked eye.

对肉眼而言，细菌是看不见。

We make them bigger so that we can see them.

经过放大使我们肉眼可以看见这些变化。

Yeah, I eyeballed the space. It really should fit easily.

我肉眼量过，应该能轻松通过。

It's invisible to the naked eye.

因为它是肉眼不可见。

They live in the same range and are indistinguishable to the human eye.

它们生活在同一范围内，肉眼难以分辨。

Infrared waves are electromagnetic energy that cannot be seen with the human eye.

红外线是肉眼看不电磁波。

However, that's just what you can see with the naked eye.

然而，这只是你用肉眼所能看。

When you're seeing the visible you're really seeing the surface of the sun.

一般用肉眼观察只看得太阳表面。

I can see the cities on it with my naked eye.

上面城市密布， 我用肉眼就能看。

You can see the lesions in infected lung tissue with the naked eye.

你可以用肉眼看被感染肺组织中病变。

Seeing satellites from the ground with the naked eye is nothing new.

在地面肉眼观看这些卫星并不是什么新鲜事。