considering everything he's seen over the years, what he has seen since King Duncan's death makes it all pale in comparison. Even compared with the "hours dreadful and things strange" he's seen in the seventy years he can recall, the night before scares him more.

Ross agrees with him. He points out that "the heavens, as troubled with man's act / Threatens his bloody stage," showing the ominous nature of the weather and skies. He says that it's dark outside when it should be light; he wonders whether night is strong or day is weak.

The old man chimes in and agrees that the current situation is unnatural. He says that the previous Tuesday, a falcon was caught by an owl. Ross says that King Duncan's horses suddenly became wild as if "they would / Make war with mankind." The old man says the horses ate each other; Ross agrees, saying he saw it himself.

This conversation illustrates the response of the natural world to the unnatural act of murder. All of these actions, in this way, mirror Macbeth's murder of King Duncan—such as the owl catching the falcon or night overtaking day. 

This dialogue comes directly after the murder of King Duncan, at the very end of Act II. Generally, they are discussing the unnatural nature of the killing and how the weirdness of it all is reflected in the natural events surrounding it: the bizarre darkness of the day; that a large falcon was harassed and killed by a much smaller bird; that the king's horses attacked and bit each other. All of these references are meant to show how deeply the world is troubled by the awful, bloody murder that has just occurred.

OLD MAN:

Threescore and ten I can remember well:

Within the volume of which time I have seen

Hours dreadful and things strange, but this sore night

Hath trifled former knowings.

ROSS:

Ah, good father,

Thou seest the heavens, as troubled with man's act,

Threaten his bloody stage. By the clock ’tis day,

And yet dark night strangles the travelling lamp.

Is't night's predominance, or the day's shame,

That darkness does the face of earth entomb,

When living light should kiss it?

OLD MAN:

’Tis unnatural,

Even like the deed that's done. On Tuesday last

A falcon towering in her pride of place

Was by a mousing owl hawk'd at and kill'd.

ROSS:

And Duncan's horses—a thing most strange and

certain—

Beauteous and swift, the minions of their race,

Turn'd wild in nature, broke their stalls, flung out,

Contending ’gainst obedience, as they would make

War with mankind.

OLD MAN:

’Tis said they eat each other.