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Hello and welcome to the Spectator's Book Club podcast. I'm Sam Leith, the literary editor of The Spectator, and I'm very pleased this week to be joined by the science writer

Carl Zimmer, whose new book is Airborne, the Hidden History of the Life We Breathe.

Carl, this is a book about something, a term that won't be familiar to everybody.

We call the aerobiome, this invisible zoo of organisms, which swirls around us all the time.

And though obviously it's given a special kind of edge by its discussion of COVID,

which you begin to end it, there's a long history here, isn't there?

And one of your starting points is Louis Pasteur wandering around the top of a glacier.

Tell me why we come in there.

Well, we think of Louis Pasteur as a person who, you know,

helped to develop the germ theory of disease and made rabies vaccines

and was this very much a medical pioneer.

But he also had this other side, which was much more kind of

wondering what is around us in the air. I mean, this was a very important part of his work

that has gotten forgotten. And he became convinced in the 1850s that the air around us was full of what he called floating germs.

This was how he would explain, for example, you know, how things would ferment,

that you have these germs floating around.

They would settle into things and they might turn butter rancid or might turn, you know,

another liquid into beer or wine. And,

...