1. means explanation: dashes can be used to explain the previous content and further elaborate the later content. For example, "Thinking about the universe and human beings" in "Daydream in the Night Sky-Thinking about the universe and human beings" is a concrete explanation of "Daydream in the Night Sky".
2. indicate the change of topic: dashes can indicate the change of topic. For example, "Daydream in the Night Sky-Viewing the Universe from the Earth" is a shift from the topic of "Daydream in the Night Sky" to the topic of "Viewing the Universe from the Earth".
3. Indicates the inserted content: Dashes can also be used to indicate the inserted content. For example, in Daydream in the Night Sky-My Personal Experience and Feeling, my personal experience and feeling was inserted into the theme of Daydream in the Night Sky.
Therefore, the role of dashes in Daydream in the Night Sky may indicate the explanation of the last article, the change of topic and the inserted content. The specific usage should be judged in combination with the context.