In "Macbeth," what is the effect of the old man's remarks in Act II, Scene 4?

The Old Man and Ross discuss events that have been happening since King Duncan was killed. The Old Man says that he has not seen anything like recent events in his 70 years. For instance, the day is very dark, as if it is night. Also, he recounts how the king's horses ate each other while in a frenzy. Ross tells of an owl that ate a falcon. All of these events of symbolic representations of Duncan's murder. The owl, for example, typically eats mice. The fact that it attacked a falcon is extraordinary because the falcon is a much more powerful animal. Macbeth acted in the same way by attacking a more powerful person.

Also, when the men discuss the weather, Ross says, "Is't night's predominance, or the day's shame, /That darkness does the face of earth entomb, /When living light should kiss it?" Ross is asking if the day is dark because the light is ashamed to show itself or if it is because darkness is too powerful that the light cannot show itself. This also refers back to Macbeth's actions, since they certainly could be considered evil and dark.