Carl Zimmer

and he could culture it, and he consistently found it, and, you know, when he injected animals with it, it just didn't quite work.

Yeah, they really are.

And although, you know, by the time they had died, you know, around 1960,

They were pretty much forgotten already.

And yet, in the 1930s, the two of them, first at Harvard and then at the University of Pennsylvania, did some incredible work to actually challenge

this idea that that airborne infection was not anything real or at least nothing really to worry about because once the miasmas have been cleared away people who embrace the germ theory of disease said look we've got cholera and water we've got yellow fever and mosquitoes we've got syphilis and sex we have all these ways that germs can get from one person to the next

We don't need to worry about the air anymore.

Relax.

And William Wells thought, I don't know if that's true.

And he actually invented a new device for actually sampling the air, a very clever kind of centrifuge.

And he started to discover, actually, there's a lot of stuff floating around in the air.

And then he then, with a medical student of his, Richard Riley, started to develop a physical model.

How does this happen?

Well...

You and I are talking.

As we are talking, we are expelling tiny droplets.

And those droplets can potentially contain pathogens.

We can sneeze out big droplets or cough them too.

Really big droplets might fall to the floor, but lots of other droplets will float.

They might be pushed along by our breath, like in a cloud, or they just may be so light, they just resist gravity.