This is a very odd scene. Shakespeare likes to include the supernatural in his work (the ghost in Hamlet, witches in Macbeth), and he certainly appears to have had fun with this scene.
In Act 1, Scene 3, several important characters (Cassius, Casca, etc.) are walking about the Capitol at night. All sorts of strange impossible things are going on. Cassius interprets the unusual events as a warning from heaven that Caesar has grown too strong.
However, in Act 2 Scene 2, Calpurnia interprets the events in quite a different way. She believes they portend danger to Caesar:
When beggars die, there are no comets seen; The heavens themselves blaze forth the death of princes.
She also reports that others have seen the following amazing things:
- A lioness hath whelped in the streets.
- Graves yawn’d, and yielded up their dead
- Fierce fiery warriors fight upon the clouds,
- The noise of battle hurtled in the air,
- Ghosts did shriek and squeal about the streets.
Calpurnia tries valiantly to talk Caesar out of going to the Capitol, and nearly succeeds. However, another character, Decius, comes and appeals to Caesar’s sense of vanity. Decius flatters Caesar into leaving the house and going to the Capitol, and the rest is history.