>> in the clean chapter, basic idea of a clean glass of drinking water, central to ghost map as a book, that we live in a world for the most part here in the developed world where you go to the faucet and you get a glass of drinking party and drink and it you don't ever think about dying of cholera 48 hours later. and that is an incredible achievement. that you can live in a city of a million people or 10 million people and have that security. that took a whole history of invention and ingenuity and scientific breakthroughs and engineering projects to make that possible. and while we celebrate innovation in our society all the time. everybody wants to talk about silicon valley and the next

apple gadget and all of that, which is great and i love those things and they're worth celebrating. we don't spend enough time talking about the people who made that clean glass of drinking water part of our lives. so i want to with this book stop and look at these objects go back and tell these stories, and also to talk about the kind of unexpected places that these technologies ultimately led us. this is the idea of the hummingbird effect. elaborate metaphor for nature. i was writing the book in california and we have hummingbirds in our garden and i was obsessed with them and how they worked and crazy anatomy. and the hummingbird evolved in an interesting play. you have flowering plants and insect developed this complicated dance of pollennation, but it's a connection that doesn't really have anything to do with birds. and then all of a sudden this

bird kind of over time figures out there's a way to get in on the action of all this nectar but has to evolve this wing structure to be able to hover right next to a flowering plant so what seems to be realizationship between insects and plants turns tout france form the a nat my of a bird. -- anatomy of a bird, and scientific history hat a similar pattern. someone trying to solve a specific problem in one field ended up either setting in motion a series of changes or new approaches or new platforms that transform the world in all these unpredictable ways. that's the hummingbird effect. in the history of clean drinking water we end the episode and the chapter with a visit to the texas instruments chip plant in austin, texas. you can see me in that claim. i'm dressed in a space suit. and this place is one of the cleanest environments on the

face of the earth where they make the microships and when you get seeded up you generally assume you're being protected from something. youer going into some kind of contaminated zone. in the clean room, you are the contaminant. the dirt. and they have to protect the chips from you. and so you dress up. you can't even use soap because soap is do dirty. it sets often part tells and its turns out that one of the thing that is essential to the clean room and the manufacture of these chips is what the call ultraclean water, which is water that is just pure h2o, and it in fact paradoxically is so clean that human beings can't -- not really safe for human beings to drink it. normal drinking water has minerals in it. so if you drink this, it will be bad for you. we wanted know drink it for the show. the producers were like, steven can drink it. we have insurance. but they wouldn't let me even taste it. it's required to do these kind

of final residencing of the microchips, and so in a sense, this technology of making our water clean that we think of in terms of, nice drinking water, and being able to take a shower or bath or something like that, butanals a funny way makes the digital revolution possible.

>> up next, "after words" with guest host, sally gwynn. this week, claimed religious author, karen arm strong, and her book hi pi fields of blood. " she argues the formation of religion involves bloodshed. this program is about an hour. >> karen, hi. i'm so glad that you could join us this morning. i have to say i'm stunned that you managed to put out one of these