For the physicist Carlo Rovelli infinity is ignorance. It belongs to those “who remain satisfied with their own ignorance, who call infinite that which we don’t understand and delegate knowledge to elsewhere.”
Rovelli, an Italian, must have been brought up a Catholic and so would have herd the questions he describes as “stupendous” that open the book of Ecclesiasticus:
Who can number the sand of the sea, and the drops of rain, and the days of eternity? Who can find out the height of heaven, and the breadth of the earth, and the deep and wisdom?
The passage emphasises the puniness of man, how we must bow down to God (via the Catholic church), and how we must not have the effrontery to try and answer those questions. But I imagine the young Rovelli standing up in the church and shouting “I can.” His mother would slap him and embarrassed haul him the church.
But he wouldn’t have been the first to be so audacious. Archimedes soon after Eccliasticus was written wrote The Sand Reckoner and argued that the number of grains of sand is “finite and can be determined.” He doesn’t claim to be able to answer the question exactly, but his play full book “is rebellion against the renunciation of the desire to know: a declaration of faith in the comprehensibility of the world.”
Rovelli regrets that Eccliasticus, representing ignorance, has spread so widely through religion while The Sand Reckoner, representing the enthusiasm to learn and understand, is poorly known.
There may be more than 100 billion galaxies each with 100 billion stars, but modern quantum physics has abolished the idea of the infinite (and so of God?). Rovelli ends with a poetic flourish, which perhaps backfires: “The only truly infinite thing is our ignorance.”