Andrea makes it to the border of Italy. There’s a moment of trouble with the guards there, who must search his belongings. However, when Andrea attests that they’re mostly books, the guards agree it’s too much trouble to go through them. There can’t be anything dangerous in books, they decide, as they let Andrea pass.
The play’s final moment comes with a touch of tongue-in-cheek irony. Furthermore, it can end with such little closure because the text itself is largely biographical. The audience knows that Galileo’s word got out and his “infection” spread to all corners of the globe.