On a cold night, there is no light, but there is a' real' charm. The vast blue sky (space) is as clear and bright as a mirror, and it is very interesting to wander among it.
The first half of this poem says that there is no light on a cold night, which explains a natural environment without fireworks, which is very suitable for people to look up at the stars. The second half of the sentence becomes immortal, which is a scene where the poet looks up at the starry sky, watches endless celestial phenomena and obsesses about it. The whole poem shows a kind of love for nature and awe and obsession with the vast universe.