[RADIOLAB INTRO]

JAD ABUMRAD: Okay. Hey, I'm Jad Abumrad.

ROBERT KRULWICH: I'm Robert. Krulwich.

JAD: This is Radiolab. And today on the program ...

ROBERT: Today is the weights and measures show. I forgot to give you the memo.

JAD: Yeah?

ROBERT: This is the day where we're gonna weigh and measure, weigh, measure, weigh and measure, and then ask deeper questions.

JAD: Yes. Right.

ROBERT: So, you know, like, how much do you weigh?

JAD: I'm not gonna say that on the air. I mean, I weigh exactly what I should weigh for my ...

ROBERT: For your financial sensibility?

JAD: [laughs] For my financial sensibility.

ROBERT: Well, let me ask you a tougher question.

JAD: Yeah?

ROBERT: How is it we can weigh anything at all? Anywhere at all? What is weight, anyway?

JAD: You mean like existentially? How it is—what is weight?

ROBERT: Well, we're gonna get a little existential.

JAD: That's a hard question. It's a deep question.

ROBERT: Well, it's hard for you. But I found someone for whom it is less than hard. It is, in fact, kind of easy.

ANDREW MARANTZ: I actually brought a list.

ROBERT: Okay, why don't you share with me your list?

ANDREW MARANTZ: Where is this thing?

ROBERT: This is Andrew Marantz. He's a writer and editor at the New Yorker Magazine, and he recently got obsessed with a—it's a list of measurements.

ANDREW MARANTZ: They're SI base units. The Système International, you know ...

ROBERT: So let me do it this way: have you ever wondered how long an inch is? I mean, exactly how long?

JAD: I know. I just look at a ruler.

ROBERT: Well, but how do you know that your ruler and my ruler have the same amount of inch space, or that someone in China, that their inch is our inch, as your inch is my inch?

JAD: I haven't really thought about it, but I'd just assume that there's like a master inch somewhere?

ROBERT: Bien sûr! I say it in French for a reason, and which you'll feel in a moment. That is what was on this list that Andrew was looking at. It's a list of standard measures for everything we have around. How big something is, how far something is, how hot something is, it's all on this list.

ANDREW MARANTZ: Okay, a meter. A meter is a fraction of a second of the distance traveled by light in a vacuum.

ROBERT: Okay.

JAD: What?

ANDREW MARANTZ: A second is how much radiation corresponds to the transition between two hyperfine levels of the ground state of the cesium-133 atom.

JAD: That's the definition of a second?

ROBERT: How many times does that particular atom jiggle?

JAD: Yeah.

ANDREW MARANTZ: Well, an ampere, which measures electric current ...

ROBERT: You know, an amp.

ANDREW MARANTZ: ... is a constant current which, if maintained in two straight parallel conductors of infinite length, would produce between these conductors a force equal to 2 times 10 to the negative 7th newtons per meter of length. I have no idea what that means.

ROBERT: See, that's the thing. If you look at the actual definitions of any of these things: amp, meter, second, whatever, you go ...

[opera singing]

ROBERT: But there is one standard on the list that is unique for its simplicity.

ANDREW MARANTZ: The definition of the standard unit of measurement that is a kilogram is ...

ROBERT: No math. No numbers.

ANDREW MARANTZ: It is a thing.

ROBERT: A particular thing?

ANDREW MARANTZ: A plum-sized thing.

ROBERT: It is the only thing we use to measure things. It's the last one standing, the only physical standard left.

JAD: Why is it the last? And why were there—is it—what? Wait, what?

ROBERT: [laughs] Let me just take you back to the beginning of the story.

LATIF NASSER: Like, I must admit that I expected this story to be a lot more boring than I found. It's like an epic story. It's really ...

ROBERT: That is Latif Nasser, science historian, regular on our show. And he says if you go all the way back to the very first farmers back in Mesopotamia ...

LATIF: All of the earliest measurements were super intuitive.

ROBERT: And he says a lot of them ...

LATIF: ... came from the body.

ROBERT: As in, "That bunny is coming close to the net." "How close, Dad?"

LATIF: Two hands. But it's not just, like—because we think of, like, hands and feet, but it was also there were so many other kinds of measurements. Like, you would say, "Oh, something is as far as, you know, my voice can carry." Or that "Something is as far as I can see sitting on the top of a camel. Or "Something is as far as I can throw a stone."

ROBERT: So that would mean, like, say, okay, I'm going to build a farm here, and I'm gonna do it three throws-a-rocks across?

LATIF: Yeah, yeah. the way I read about it was, like, travelers. Like, if you're a Saharan traveler, you know, and you need to know where the next watering hole is, that's kind of a life-and-death measurement.

ROBERT: Yeah.

LATIF: And they would say it's, you know, three throw-a-rocks away or it's 10 throw-a-rocks away.

ROBERT: But, you know, there might be some built-in uncertainty there because if you ask Achilles ...

LATIF: Yeah.

ROBERT: It could be two throw-a-rocks away. But he asked me would be, like, 78.

LATIF: You have nailed exactly the problem with the throw-a-rock system.

ROBERT: And these problems kind of came to a head in the 1700s.

LATIF: It's the eve of the French Revolution.

ROBERT: In a little town called Paris.

LATIF: It's a pretty cosmopolitan place, which means that people are coming from different places, and they all have their own measures. Approximately 250,000 different units of measurement in regular use.

ROBERT: 250,000!

LATIF: Every commodity has its own measure. So you have grain, wine, oil, salt, hay, coal, wood, fabric, everything. And it's extraordinarily confusing.

ROBERT: Not to mention it's extraordinarily bad for trade. So if I came to you and I said, "Monsieur, I have a bit of cloth." You would say, "How much cloth you got?" And I'd say, "I have two yards." And you'd say, "What's a yard?" I'd say, "It's this much." And the other guy would say, "No, no. It's this much." And I'd say, "No, no. It's this much!" And then he'd go, "No, no. It's this much!" And you could see that ...

JAD: [laughs] Frustrating.

ROBERT: It was frustrating.

LATIF: Yeah.

ROBERT: And making matters worse ...

LATIF: In the 1780s, there was a famine. So there was a shortage of grain, and people were hungry and people were angry. To the bakers at the time, they knew that if they raised the price of bread, like, an angry mob would basically come and kill them.

ROBERT: But they also knew that with no absolute standard, there was no way to be sure that what you were getting is what you were getting.

LATIF: And so what they started doing was they started just lightening their bread loaves by just a little. So as the famine got worse, people would be waiting in longer and longer lines to pay the same amount of money for smaller and smaller loaves. And so one of the things that people are, like, crying out for is that they want standardized weights and measures. Don't short me on this. This is serious.

ROBERT: Well, you know what happens next.

LATIF: The Bastille is stormed, and the king is under house arrest. And then under the guillotine.

ROBERT: And as soon as the revolutionary government takes over, they say, "All right."

LATIF: "Okay, this is one of our first priorities. We are going to make a new standard."

ROBERT: But not based on something arbitrary like a king. This is The Enlightenment.

LATIF: Why don't we draw on some kind of totally different authority? The authority of nature.

ROBERT: Of nature.

LATIF: Of nature.

ROBERT: So long story short, they took the circumference of the Earth. They took a quarter of that circumference divided that by 10 million, and they got the meter. The meter they then divided by 10, cubed it, filled the cube with water, took the mass of the water, minted a cylinder of metal with that mass and voila, they created the world's first kilogram.

LATIF: The idea of this was if we make this thing that is so beautiful and perfect and everybody can see it that way, then not only will France use it but the whole world will use it. Then goods and ideas can be exchanged everywhere by all people, and it will be a beautiful day.

ROBERT: Liberté, fraternité, égalité.

LATIF: Exactly. They wanted something that would be eternal and unchanging for everybody for all time.

ROBERT: So now I guess you want to see it, no?

JAD: Yeah!

ROBERT: Okay!

PATRICK ABBOTT: Okay, so it's in here.

ROBERT: We ended up visiting the National Institute of Standards and Technology in Maryland.

PATRICK ABBOTT: And this is where we'll be going in. But we're gonna go ...

ROBERT: And this guy ...

PATRICK ABBOTT: Patrick Abbott, physicist.

ROBERT: ... was our guide. They took us three stories down into the bedrock of the state of Maryland, because they want things down here to be totally still.

ROBERT: We've just gone through one double door. Here comes another double door. Oh, let me step into this vault of a room. And there it was. What we're looking at then is a glass jar with a little handle on top. And then inside that is another glass jar with a little handle on top and inside that is ...

PATRICK ABBOTT: Is the thing.

ROBERT: The thing. It's kind of gorgeous, really.

ROBERT: The shiniest little cylinder you've ever seen.

ROBERT: Very small, and it looks very clean.

ROBERT: And this isn't even really the real one. The original of the original of the original of the original ...

PATRICK ABBOTT: "Le Grand K," as they call it.

ROBERT: Lives in a basement in France. You can't get anywhere near that one.

PATRICK ABBOTT: The international prototype is ...

ROBERT: The big Kahuna. That's the one used to calibrate six identical platinum cylinders.

PATRICK ABBOTT: What they call witnesses or témoins in French.

ROBERT: Those witnesses are then used to calibrate another set of cylinders, which are then used to calibrate the US standards, which is what we saw. And that one is used to calibrate all kinds of things: the weight of your lemons, the scale in your bathroom.

[ARCHIVE CLIP, The Biggest Loser: Green tea, and you lost 34 pounds.]

ROBERT: And every time somebody loses a pound on that TV show Biggest Loser ...

[ARCHIVE CLIP, The Biggest Loser: 5.87 percent.]

ROBERT: You can actually trace that like a ...

PATRICK ABBOTT: Bloodline if you will, or an unbroken chain back to the international prototype kilogram.

ROBERT: To a single object in a basement in France. The holy of holies that is the kilogram.

JAD: Wait, you're telling me that when something is weighed in the world, often it goes all the way back to this one hunk of metal?

ROBERT: That's what I'm saying. Which was why the next part of the story is so disconcerting.

ANDREW MARANTZ: What happened in 1989 ...

ROBERT: ... is that according to Andrew, the folks who take care of the official kilogram ...

ANDREW MARANTZ: The Big K.

ROBERT: They took it out of its jars.

ANDREW MARANTZ: They put it in a steam bath. Hit it with the steam that rinses everything. Wait for it to dry. Then ...

ROBERT: ... they commence a ceremonial weighing.

ANDREW MARANTZ: Right.

ROBERT: But how do you weigh the thing that is the standard of weight?

ANDREW MARANTZ: Well, you weigh it against the copies.

ROBERT: Like the US copy, for example. So they get one of those, and they put it on one side of the scale and they put the Grand K on the other.

ANDREW MARANTZ: And the IPK, the Le Grand K, the one—is light.

[opera singing]

JAD: What?

ROBERT: It's light.

ANDREW MARANTZ: It doesn't ...

ROBERT: How many—how much lighter is it than its sisters?

ANDREW MARANTZ: Roughly the mass of a grain of sugar.

ROBERT: Oh!

ANDREW MARANTZ: Yeah. So ...

ROBERT: Is that gigantic?

ANDREW MARANTZ: It's measurable.

JAD: Wait, how do they know that it was light and not that the other ones were heavier?

ANDREW MARANTZ: Right. Well, they didn't. So they used the second sister copy.

ROBERT: Still light.

ANDREW MARANTZ: And the third sister copy.

ROBERT: Still light.

ANDREW MARANTZ: And the fourth and fifth and sixth.

ROBERT: In comes the man from Germany.

ANDREW MARANTZ: Light.

ROBERT: In comes the man from Canada.

ANDREW MARANTZ: Light.

ROBERT: In comes the man from Spain.

ANDREW MARANTZ: Light.

ROBERT: Which led them to the troubling possibility that the international standard for weight was losing weight.

ANDREW MARANTZ: Well, we think that. We think the big guy's the problem. As far as how it lost that weight, really no one knows.

ROBERT: One possibility is it got cleaned too much and maybe some of it got scraped away.

ANDREW MARANTZ: Although it's disputed whether cleaning it more would make it lose weight or gain weight. The other theory is outgassing.

ROBERT: Like maybe a little hydrogen is seeping out of the metal.

ANDREW MARANTZ: And then there was one thing I read that said "Foul play cannot be ruled out."

ROBERT: Well, see, I was thinking maybe the Taliban.

ANDREW MARANTZ: [laughs]

ROBERT: What's clear is we may have a slightly trippy situation here. We got a hunk of metal losing weight, and yet because it is the standard ...

ANDREW MARANTZ: It still weighs exactly a kilogram, right? If the definition of a kilogram is the mass of the International Prototype Kilogram, whatever happens when you put that thing on the scale, that's a kilogram.

ROBERT: You can't do that!

ANDREW MARANTZ: And then everything else in the world is wrong.

ROBERT: No, you can't. That's ridiculous.

ANDREW MARANTZ: It's like, that doesn't sit right. That's like something that, like, the North Korean government would do. It'd just be like, "No more cash!" Like, we can't just go around capriciously doing stuff like that.

JAD: All right. So if the standard of weight is, as you're saying, losing weight, so how do you fix that?

ROBERT: Well ...

JOHN PRATT: I'm getting zero cell phone reception down here. That means we're really deep.

ROBERT: When we were down in that underground room in Maryland, we met a guy who has some thoughts about this.

JOHN PRATT: Oh, there he is. Okay.

ROBERT: His name's John Pratt.

JOHN PRATT: I'm the leader of the fundamental electrical measurements group at the National Institute of Standards and Technology.

LYNN: Hi, John.

ROBERT: John walked us through even more high-security doors, and then we walked into this ...

ROBERT: Oh, my God!

ROBERT: … amazing room!

ROBERT: It is big!

ROBERT: About three stories tall.

ROBERT: You know, and it's made of—it's like a silver room. And it has a silver-gray floor. It has silver, shiny walls. And your hair is on the silver-y side.

JOHN PRATT: Very much so.

ROBERT: You probably wouldn't be allowed in here if you were a redhead.

JOHN PRATT: No, no.

ROBERT: I don't even know how to describe it. It looks like a wheel turned on its side with ...

ANDREW MARANTZ: The thing itself looked sort of just like a massive, round, metal cauldron or, like, a big metal pot. But then there are all these weird little gizmos and parts, and then all these coiled-up wires, and ...

ROBERT: It's just a stunning machine.

ANDREW MARANTZ: But it's all just for the benefit of the one.

JOHN PRATT: The one measure.

ANDREW MARANTZ: The one kilogram.

JOHN PRATT: Yep.

ROBERT: Because inside that giant cauldron, there is an extremely, extremely sensitive ...

JOHN PRATT: Balance. An equal arm balance.

ROBERT: Which is basically like a seesaw.

JOHN PRATT: Or a teeter-totter. And usually you would set that up so that you would literally put kid on one side of the teeter-totter, kid on the other side of the teeter-totter.

ROBERT: Now you've been in a playground, so you know how this goes. But what they've done here is on one side of the teeter-totter, they've got the kilogram, like, the Grand K. That's kid number one. On the other side, instead of another kilogram or kid two ...

JOHN PRATT: We'll have a highly variable magnet.

ROBERT: Now here's the thing. The magnet won't be touching that side of the scale, it'll be exerting a force, an invisible force on that side.

JOHN PRATT: It'll produce a force. And we could use that to hold the balance still.

ROBERT: And the force it takes to hold up the balance? That, of course, is the same as the weight of the Grand K sitting on the other side. And if you can convert that force into a number that everybody agrees to?

JOHN PRATT: Voila!

ROBERT: You have just redefined the kilogram. You have wrenched it from the world of things, and it's become attached to the fundamental forces of the universe.

JOHN PRATT: Yep, you've grasped the gist of it.

JAD: So if they're able to do that, does that mean that the Grand K's reign is done?

ROBERT: Not yet, no. Because first of all, you have to get straight with a lot of math.

ANDREW MARANTZ: MC2 = H\nu. Work backwards.

ROBERT: You've got to divide by E, and then by M.

ANDREW MARANTZ: Measure the B field. Whoo, let's go!

ROBERT: And then you get your amperes, and your watts and your Planck's constant.

ANDREW MARANTZ: Classical Bohr model of atoms and stuff. Anyway ...

ROBERT: It is actually way more complicated, this whole thing, than I frankly will ever understand, but here's where we are at: you got all these different teams around the world. You got John's team in Maryland with his seesaw. You got another lab—actually, a couple of them—that have their seesaws. You got a third lab that's literally counting the atoms. They're all doing experiments, comparing numbers, trying to get the numbers to agree so that by whatever route everybody agrees on exactly what a kilogram is. Right now, they're close. They're in agreement out to about six decimal places. And that's not good enough. They want the numbers to be out to eight decimal places. But if they can do that, then and only then will the Grand K be no more.

ANDREW MARANTZ: Yeah.

ROBERT: Because instead of defining the kilogram as whatever is equal to the Grand K, now you have a new definition.

ANDREW MARANTZ: The new definition of the kilogram: the kilogram is the SI unit of the mass. Its magnitude is set by fixing the numerical value of the Planck constant vehicle to exactly 6.626069. And we have Xs because we haven't all agreed with the final ...

PATRICK ABBOTT: Those are the missing decimals.

ANDREW MARANTZ: Those are the missing decimal places. Times 10 to the minus 34. One is expressed in the unit for actions Joule seconds, which is a meter squared kilogram per second.

PATRICK ABBOTT: Whew! That'll be such a simpler definition.

ANDREW MARANTZ: Oh, yeah.

PATRICK ABBOTT: [laughs]

JAD: And what will happen to the Grand K when the new definition goes into effect?

ROBERT: Well now, so this is the sad part.

SORINE FASSEAU: Vous avez par exemple.

ROBERT: It looks like a church.

SORINE FASSEAU: You will see after.

ROBERT: The Grand K may eventually end up in a place like this, where so many standards have gone to die. This is the Musée des Arts et Métiers.

SORINE FASSEAU: À Paris.

ROBERT: In Paris.

SORINE FASSEAU: So this is the beginning.

ROBERT: Sorine Fasseau is our tour guide.

ROBERT: Yeah. What is this?

SORINE FASSEAU: A litre.

ROBERT: He showed us the original liter.

SORINE FASSEAU: Ou alors, ça c'est 0,8 litre.

ROBERT: Wow!

ROBERT: Some early thermometers.

SORINE FASSEAU: Il y'a un objet qui est peut-être drôle.

ROBERT: In one room, he showed us the original—I think it was the Parisian meter. So in Paris, this was the infallible, the absolute standard.

SORINE FASSEAU: From 1801, I think.

ROBERT: It's in a wooden box with a velvet packing, and it's got silk ribbons at either end. And it's just a very beautiful looking silver rod. [laughs]

JAD: Aw, to imagine, like, the thing, the grand thing being in this place, it's sort of like seeing the Pope in shorts or something. It makes me a little uncomfortable.

ROBERT: [laughs] Special thanks to ...

[OPERA SINGER: Ari Adland.]

ROBERT: ... and ...

[OPERA SINGER: Eric Perlmutter.]

ROBERT: And also to ...

[OPERA SINGER: Terry Quinn.]

ROBERT: We don't wanna forget ...

[OPERA SINGER: Richard Davis.]

ROBERT: And ...

[OPERA SINGER: Ken Alder, Bob Waters, Michael Bell, Michael Newman.]

ROBERT: And finally ...

JAD: Thank you to our math angel, soprano ...

[OPERA SINGER: Melissa Hughes. [laughs] Very weird to sing my own name.]

JAD: Also big props to reporter Andrew Marantz, Latif Nasser and our producer Lynn Levy. Up next, we go to Facebook. And they figured out a way perhaps to make us nicer to another. The question is, is that benevolent, or a sinister game of social engineering? You decide. That's up next.

JAD: Hey, I'm Jad Abumrad.

ROBERT: I'm Robert Krulwich.

JAD: This is Radiolab. And this hour we've been sizing up the world, looking at how standards for weights and measures were developed and then dismantled.

ROBERT: Yeah, and now we're gonna turn to Facebook which as some of you know has been doing its own measuring and its own comparing and its own weighing of—well, us, actually.

JAD: Yeah.

ROBERT: Because we are oftentimes their lab rats.

JAD: Yeah, this is a story we've been following for a while. Comes from a friend of mine Andrew Zolli, and he's a guy who thinks a lot about technology.

ANDREW ZOLLI: I have been interested for a long time in the relationship between technology and emotion because, well, I've thrown more than one cell phone to the ground. [laughs]

JAD: Andrew and I were having breakfast one day, and he pitched me on this idea of doing a story about Facebook.

ROBERT: I remember.

JAD: But this story was wickedly interesting and profound in its way. It really begins in 2011.

ANDREW ZOLLI: Well, let me back up for a minute. One of the challenges talking about Facebook is just the scale of the thing. So, you know, there's 1.3 billion people on Earth as of March, 2014.

JAD: Wow.

ANDREW ZOLLI: Those are active monthly users. There's a billion people who access the site through mobile devices. Just to put that in perspective, there's more Facebook users than there are Catholics on Earth.

JAD: That can't be true.

ANDREW ZOLLI: Yeah.

JAD: No!

ANDREW ZOLLI: Yeah.

JAD: It turns out it is true. But they're neck and neck. Anyhow, the overall point is that when you have one out of every seven people on the planet in the same space trying to connect across time and geography ...

ANDREW ZOLLI: You are bound to create problems, sometimes.

[NEWS CLIP: Facebook making headlines again tonight. The issue this time? Privacy.]

JAD: Before we go there, we should introduce you to the guy in our story who is the problem solver.

ARTURO BEJAR: My name is Arturo Bejar, and I'm a director of engineering at Facebook.

JAD: His story begins Christmas, 2011.

ANDREW ZOLLI: People are doing what they do every holiday season, they're getting back together with their families and they're going to family parties, and they're taking lots and lots of pictures, and they're all uploading them to Facebook.

ARTURO BEJAR: And at the time, the number of photos that were getting uploaded was going pretty crazy.

JAD: In fact, in just those few days between Christmas and New Year's ...

ANDREW ZOLLI: There are more images uploaded to Facebook ...

ARTURO BEJAR: ... than there were the entirety of Flikr.

JAD: Wait. You're saying more images were uploaded in a week to Facebook than all of Flickr all time?

ARTURO BEJAR: Yeah.

ROBERT: Whoa!

JAD: Which created a situation.

ARTURO BEJAR: The number of photos was going up, and along with the number of photos going up, the number of reports was going up.

ANDREW ZOLLI: What he means by reports is this ...

JAD: Back in 2011 ...

ANDREW ZOLLI: If you saw something on Facebook that really upset you, you could click a button to report it.

JAD: You could tell Facebook to take it down, which from their perspective is a really important mechanism because if you're Facebook, you don't want certain kinds of content on your site.

ARTURO BEJAR: You don't want nudity. You don't want, like, drug use, hate speech, things like that.

ANDREW ZOLLI: So a day or so after Christmas ...

JAD: Thereabouts.

ANDREW ZOLLI: Facebook engineers come back to work and they find waiting for them literally millions of photo reports.

ARTURO BEJAR: Yes. The number of people that would be necessary to review everything that was coming in, it kind of boggled the mind.

JAD: How many people would you have needed?

ARTURO BEJAR: I think at the time we were looking at it, which is two years ago, and again, all this has grown much since then, we're looking at, like, thousands.

JAD: When a photo was reported, a human being has to look at it.

ARTURO BEJAR: Exactly right. Because there needs to be a judgment on the image, and humans are the best at that.

ANDREW ZOLLI: So Arturo decided before we do anything, let's just figure out what we're dealing with.

ARTURO BEJAR: And so we sat down with a team of people, and we started going through the photos that people were reporting.

JAD: And what they found was that about 97 percent of these million or so photo reports were drastically miscategorized.

ROBERT: [laughs]

JAD: They were seeing moms holding little babies ...

ARTURO BEJAR: Reported for harassment.

JAD: Pictures of families in matching Christmas sweaters ...

ARTURO BEJAR: Reported for nudity. Pictures of puppies reported for hate speech.

JAD: Puppies reported as hate speech?

ARTURO BEJAR: Yes. And we're like, "What's going on," right? Hmm.

JAD: So they decide, let's investigate.

ANDREW ZOLLI: Okay, so step one for Facebook: just ask a few of these people.

ANDREW ZOLLI: Why don't you like this photo?

JAD: Responses come back, and the first thing they realize is that almost always the person complaining about the image ...

ANDREW ZOLLI: ... was in the image they were complaining about.

JAD: And they just hate the picture. Like, maybe they were doing a goofy dance, someone snapped a photo, and they're like, "Why did you post that?"

ANDREW ZOLLI: "Take it down."

JAD: Arturo said there were definitely a lot of reports from people who used to be couples.

ARTURO BEJAR: And then they broke up, and then they're asking to take the photos down. So once we've begun investigating, you find that there's all of this relationship things that happen that are, like, really complicated.

ANDREW ZOLLI: You're talking about stuff that's the kind of natural detritus of human dramas.

JAD: And the only reason that the person reporting it flagged it as, like, "hate speech" is because that was one of the only options.

ANDREW ZOLLI: They were just picking because they needed to get to the next screen to submit the report.

ARTURO BEJAR: So we added a step.

ANDREW ZOLLI: Arturo and his team set it up so that when people were choosing that option ...

ARTURO BEJAR: I want this photo to be removed from Facebook.

ANDREW ZOLLI: Some of them would see a little box on the screen ...

ARTURO BEJAR: ... that said, "How does the photo make you feel?"

ANDREW ZOLLI: And the box gave several choices.

ARTURO BEJAR: The options were: embarrassing ...

ANDREW ZOLLI: Embarrassing.

ARTURO BEJAR: ... saddening.

ANDREW ZOLLI: Upsetting.

ARTURO BEJAR: Bad photo. And then we always put in an "other ..."

ANDREW ZOLLI: Where you could write in whatever you wanted about the image.

ARTURO BEJAR: And it worked incredibly well. I mean, like, 50 percent of people would select an emotion.

JAD: Like, for instance, embarrassing.

ARTURO BEJAR: And then 34 percent of people would select "other." And we read those. We sit down and we're reading the "other," and what was the most frequent thing that people were typing into "other?" It was, "It's embarrassing."

JAD: "It's embarrassing?" But you had "embarrassing" on the list.

ARTURO BEJAR: I know.

JAD: That's weird!

ARTURO BEJAR: I know.

JAD: Arturo was like, "Okay, maybe we should just put "It's" in front of the choices?

ANDREW ZOLLI: As in, "Please describe this piece of content." "It's embarrassing."

ARTURO BEJAR: It's a bad photo of me. It makes me sad.

JAD: Etcetera.

ANDREW ZOLLI: And when they wrote out the choices that way ...

JAD: With that extra word.

ARTURO BEJAR: We went from 50 percent of people selecting an emotion to 78 percent of people selecting an emotion.

ANDREW ZOLLI: The word "It's," all by itself, boosted the response by 28 percent.

ARTURO BEJAR: From 50 to 78.

JAD: And in Facebook land, that means thousands and thousands of people.

ROBERT: I mean, just to slow down for a second, I'm trying to think of what could that be? "It's?"

JAD: Here's the thinking: it's always good to mirror the way people talk.

ROBERT: Right.

JAD: Arturo's idea though, which I find kind of interesting, is that when you just say "Embarrassing" and there's no subject, it's silently implied that you are embarrassing. But if you say, "It's embarrassing," well, then that shifts the sort of emotional energy to this ...

ROBERT: Photograph.

JAD: ... thing.

ROBERT: That thing is embarrassing. I'm fine. It's embarrassing.

JAD: It is responsible.

ROBERT: Yes.

JAD: Not me.

ROBERT: Good for Arturo. That's a subtle thought.

JAD: It's interesting, right? It's very subtle, but it still doesn't solve their basic problem because even if Facebook now knows why the person flagged the photo, that it was embarrassing and not actually hate speech, they still can't take it down.

ANDREW ZOLLI: I mean, there's nothing in the policy, the terms of service, that says you can't put up embarrassing photos.

JAD: And in fact, if they took it down they'd be violating the rights of the person who posted it.

ROBERT: Oh, so they'd actually fence themselves in a little bit.

JAD: Yeah.

ROBERT: Huh. For me, I'd always put in an "other."

JAD: I would just be like, "Go deal with it yourself," is what I would say.

ROBERT: [laughs]

JAD: Talk to the person. No, honestly, that's the solution. He wouldn't put it that way, but what he needed to have happen was for the person who posted the picture and the person who was pissed about it ...

ARTURO BEJAR: ... to talk to each other.

ANDREW ZOLLI: To work it out themselves.

JAD: So Arturo and his team made a tweak where if you said this photo was embarrassing or whatever, a new screen would pop up and it would ask ...

ARTURO BEJAR: "Do you want your friend to take the photo down?"

JAD: And if you said "Yes, I would like my stupid friend to take the photo down ..."

ARTURO BEJAR: We put up an empty message box.

ANDREW ZOLLI: Just an empty box that said, "We think it's a good idea for you to tell the person who upset you that they upset you."

ARTURO BEJAR: And only 20 percent of people would type something in and send that message.

ANDREW ZOLLI: They just didn't do it. They just said, "I'd rather you deal with this."

JAD: So Arturo and his team were like, "Okay, let's take it one step further." When that message box popped up ...

ARTURO BEJAR: We gave people a default message that we crafted ...

ANDREW ZOLLI: ... to start that conversation.

ARTURO BEJAR: Just get the conversation going. And it's kind of funny, the first version of the message that we did was like ...

ANDREW ZOLLI: "Hey, I didn't like this photo. Take it down."

ROBERT: "Hey, I don't like that photo." That's a little aggressive.

JAD: It is. But when they started presenting people with a message box with that sentence pre-written in ...

ANDREW ZOLLI: Almost immediately ...

ARTURO BEJAR: ... we went from 20 percent of people sending a message to 50 percent of people sending a message.

ROBERT: Really?

ARTURO BEJAR: It's surprising to all of us. Like, we weren't expecting to see that big of a shift.

JAD: Maybe it's just that. It's so easy to shirk the responsibility of confronting another person that you need every little stupid nudge you can get.

ROBERT: [laughs] I see. Okay.

JAD: That's how I see it.

ROBERT: Okay.

JAD: So they put out this pre-written message. It seems to really have an effect. So they're like, "Okay, if that works so well, why don't we try some different wordings?" Instead of ...

ANDREW ZOLLI: "Hey, I didn't like this photo. Take it down."

JAD: Why don't we try ...

ANDREW ZOLLI: "Hey ..."

JAD: "Robert."

ANDREW ZOLLI: "I didn't like this photo. Take it down."

JAD: Just putting in your name ...

ANDREW ZOLLI: ... works about seven percent better than leaving it out.

ROBERT: Meaning what?

ANDREW ZOLLI: It means that you're seven percent more likely either to get the person to do what you asked them to do ...

JAD: Take down the photo.

ANDREW ZOLLI: Or to start a conversation about how to resolve your feelings about it.

ROBERT: Oh, we're now measuring the effectiveness of the message.

JAD: Yep.

ROBERT: So if I'm objecting, will the other party pull it off the computer?

JAD: Pull it off, or just talk to you about it.

ROBERT: Okay.

JAD: They also tried variations like, "Hey Robert, would you please take it down?" Throwing in the word, "Please." Or "Would you mind taking it down?"

ARTURO BEJAR: And it turns out that "Would you please" performs four percent better than "Would you mind?"

JAD: They're not totally sure why.

ROBERT: Huh.

JAD: But they tried dozens of phrases like, "Would you please?" "Would you mind?" "I'm sorry to bring this up, but would you please take it down?" "I'm sorry to bring this up, but would you mind taking it down?" And at a certain point, we just wanted to see this whole process they're going through up close. So we took a trip out to Facebook headquarters, Menlo Park, California. We met up with Arturo who sort of walked us through the campus.

ARTURO BEJAR: Yeah, that's, like, the hammock. This is kind of a little, like, the terrace hangout.

JAD: It's one of these sort of, like, socialist utopic Silicon Valley campuses where people are, like, in hammocks, and there's volleyball happening. So we were there on a Friday, because every Friday afternoon Arturo assembles this really big group ...

ARTURO BEJAR: [laughs] Welcome to the meeting.

JAD: ... to review all the data. You got about 15 people crammed into a conference room. Like, technical folks.

MUSTAFA: Mustafa. Software engineering, trust engineering at Facebook.

DAN FARRELL: Dan Farrell. I'm a data scientist.

PAUL: Paul. I'm also an engineer.

JAD: A lot of these guys called themselves, "Trust Engineers." And every Friday, the trust engineers are joined by a bunch of outside scientists.

DACHER KELTNER: Dacher Keltner, professor of psychology, UC-Berkeley.

MATT KILLINGSWORTH: Matt Killingsworth. I study the causes and nature of human happiness.

EMILIANA SIMON-THOMAS: Emiliana Simon-Thomas. And my background is neuroscience.

JAD: This was the meeting where the team was reviewing all the data about these phrases, and so everybody was looking at a giant graph projected on the wall.

DAN FARRELL: It's kind of supporting your slightly U-shaped curve there, in that, especially in the deletion numbers, the "Hey, I don't like this photo, take it down," and the "Hey, I don't like this photo. Would you please take it down?" Are kind of the winners here.

EMILIANA SIMON-THOMAS: It's kind of interesting that you see the person that's receiving a more direct message is higher, 11 percent versus 4 percent.

JAD: One of the things they notice is that any time they used the word "Sorry" in a phrase, like, "Hey, Robert. Sorry to bring this up, but would you please take it down?"

ARTURO BEJAR: Turns out the "I'm sorry," It doesn't actually help. It makes the numbers go down.

ROBERT: Really?

EMILIANA SIMON-THOMAS: Seven and nine are the—some of the low points. And those are the ones that say "Sorry."

JAD: So, like, just don't apologize. Just don't apologize. But one of the things that really struck me at this meeting on a different subject is that the scientists in the room as they were looking at the graph taking in the numbers, a lot of them had this look on their face of, like, "Holy [bleep]!"

EMILIANA SIMON-THOMAS: I'm just stunned and humbled at the numbers that we generally get in these studies.

JAD: That's Emiliana Simon-Thomas from Berkeley.

EMILIANA SIMON-THOMAS: My background is in neuroscience, and I'm used to studies where we look at 20 people, and that's sufficient to say something general about how brains work.

ROB BOYLE: Like, in general at Facebook, like, people would scoff at sample sizes that small.

JAD: That's Rob Boyle, who's a project manager at Facebook.

ROB BOYLE: The magnitudes that we're used to working with are in the hundreds of thousands to millions.

JAD: And this is kind of an interesting moment because there's been a lot of criticism recently—especially in social science—about the sample sizes, how they're too small and how they're too often filled with white undergraduate college kids, and how can you generalize from that? So you could tell that some of the scientists in the room, like, for example, Dacher Keltner, who's a psychologist at UC-Berkeley, he'd be like, "Oh my God, look at what we can do now. We can get all these different people ..."

DACHER KELTNER: Of different class backgrounds, different countries.

JAD: To him, this kind of work with Facebook, this could be the future of social science right here.

DACHER KELTNER: There has never been a human community like this in human history.

JAD: And somewhere in the middle of all the excitement about the data and the speed at which they can now test things ...

ROB BOYLE: The bottleneck is no longer how fast we can test how things work, it's coming up with the right things to test.

JAD: Andrew threw out a question.

ANDREW ZOLLI: What is the statistical likelihood that I have been a guinea pig in one of your experiments?

ROB BOYLE: I believe a hundred percent. But ... [laughs]

DAN FARRELL: If you look at the zeta, any given person ...

JAD: That's Dan Farrell, data scientist.

DAN FARRELL: And when we look at the data, any given person is probably currently involved in, what, 10 different experiments? And they've been exposed to ten different experimental things.

ROB BOYLE: Yep.

ANDREW ZOLLI: That kind of blew me back a little bit. I was like, I've been a research subject and I had no idea. And I had that moment of discovery on a Friday, and literally the next day—Saturday ...

[NEWS CLIP: This is scary.]

ANDREW ZOLLI: The world had that experience.

[NEWS CLIP: Facebook using you and me as lab rats for a Facebook experiment on emotions.]

JAD: Barely a day after we'd gotten off the plane from Facebook headquarters ...

ANDREW ZOLLI: ... the kerfuffle occurred.

[NEWS CLIP: Facebook exposed for using us as lab rats.]

[NEWS CLIP: As lab rats.]

[NEWS CLIP: Lab rats, shall we say?]

[NEWS CLIP: Facebook messing with your emotion.]

JAD: You may remember the story because for a hot second it was everywhere.

[NEWS CLIP: Facebook altered the amount of ...]

JAD: It was all over Facebook. The story was, an academic paper had come out that showed that with some scientists, the company ...

[NEWS CLIP: ... had intentionally manipulated user news feeds to study a person's emotional response.]

[NEWS CLIP: Seriously. They wanted to see how emotions spread on social media.]

JAD: They basically tinkered with the newsfeeds of about 700,000 people.

[NEWS CLIP: ... 700,000 users to test how they'd react if they saw more positive versus negative posts and vice versa.]

JAD: And they found an effect, that when people saw more positive stuff in their news feeds, they would post more positive things themselves and vice versa. It was a tiny effect, tiny effect, but the results weren't really the story. The real story was that Facebook was messing with us.

[NEWS CLIP: Gives you pause, and scares me when you think that they were just doing an experiment to manipulate how people were feeling, and how they then reacted on Facebook.]

ANDREW ZOLLI: People went apoplectic.

[NEWS CLIP: It has this big brother element to it that I think people are going to be very uncomfortable with.]

ANDREW ZOLLI: And some people went so far as to argue ...

[NEWS CLIP: I wonder if Facebook killed anyone with their emotional manipulation stunt.]

ANDREW ZOLLI: If a person had a psychological or psychiatric disorder, manipulating their social world could cause them real harm.

[NEWS CLIP: Make sure you read those terms and conditions, my friends. That's the big takeaway.]

KATE CRAWFORD: What you hear is a sense of betrayal, that I really wasn't aware that this space of mine was being treated in these ways, and that I was part of your psychological experimentation.

JAD: That's Kate Crawford.

KATE CRAWFORD: I'm a principal researcher at Microsoft Research.

JAD: Visiting professor at MIT, strong critic of Facebook throughout the kerfuffle.

KATE CRAWFORD: There is a power imbalance at work. I think when we look at the way that that experiment was done, it's an example of highly-centralized power and highly-opaque power at work. And I don't want to see us in a situation where we just have to blindly trust that platforms are looking out for us. Here I'm thinking of one of—an earlier Facebook study actually, back in 2010, where they did a study looking at whether they could increase voter turnout. They had this quite simple design. They came up with, you know, a little box that would pop up and show you where your nearest voting booth was. And then they said, "Oh, well, in addition to that, when you vote here's a button, you can press it says 'I voted.' And then you'll also see the pictures of six of your friends who'd also voted that day." Would this change the number of people who went out to vote that day?

JAD: And Facebook found that it did. That if you saw a bunch of pictures of your friends who had voted, and you saw those pictures on Election Day, you were then two percent more likely to click the "I voted" button yourself, presumably because you too had gone out and voted. Now two percent might not sound like a lot, but ...

KATE CRAWFORD: It was not insignificant. Again, I think by the order of 340,000 votes were the votes that they estimate they actually shifted by getting people to go out.

JAD: Really? So these are people who wouldn't have voted who did?

KATE CRAWFORD: They wouldn't have voted, and who that—they have said in their own paper, published paper, that they increased the number of votes that day by 340,000.

JAD: Simply by saying that your neighbors did it too? 

KATE CRAWFORD: Yeah, by your friends.

JAD: Now my first reaction to this, I must admit was, okay I mean, we're at historic lows when it comes to voter turnout. This sounds like a good thing.

KATE CRAWFORD: Yes, but what happens if someone's running a platform that a lot of people are on and they say, "Hey, you know, I'm really interested in this candidate. This candidate is going to look out, not just for my interests, but the interests of the technology sector, and I think they're—you know, they're a great candidate. Why don't we just show that get out to vote message and that little system design that we have to the people who clearly—because we already have their political preferences—the ones who kind of agree with us. And the people who disagree with that candidate, they won't get those little nudges. Now that is a profound democratic power that you have.

JAD: Kate's basic position is that, when it comes to social engineering, which is what this is, companies and the people that use them need to be really, really careful. In fact, when Andrew mentioned to her that Arturo had this group and the group had a name ...

ANDREW ZOLLI: He actually runs a group called The Trust Engineering Group. His job is to engineer trust.

JAD: When Andrew told her that ...

ANDREW ZOLLI: Facebook users. That's his job.

JAD: [laughs] You're smacking your forehead.

KATE CRAWFORD: I think we call that a "facepalm." [laughs]

JAD: She facepalmed really hard.

KATE CRAWFORD: These ideas that we could somehow engineer compassion, I think, to some degree have a kind of hubris in them. Who are we to decide whether we can make somebody more compassionate or not?

ANDREW ZOLLI: How do we want to set this up?

JAD: Let's see. How do we do this?

JAD: A couple months after our first interview, we spoke to Arturo Bejar again. At this point, the kerfuffle was dying down. And we asked him about all the uproar.

JAD: I know this is not your work, the emotional contagion stuff, but literally, like, hours after we got back from that meeting, that thing erupted. Do you understand the backlash?

ARTURO BEJAR: No, I mean, I think that— I mean, we—we really care about the people who use Facebook. I mean, if anything I've learned in this work is that you really have to respect people's response and emotions, no matter what they are. There was a moment of concern of what it would mean to the work. And there was like, this is this gonna—is this gonna mean that we can't do this?

JAD: Hmm.

ARTURO BEJAR: Part of me, like, coming here is I actually want to reclaim back the word "emotion," and reclaim back the ability to do very thoughtful and careful experiments. I want to claim back the word "experiment ..."

JAD: You want to reclaim it from what?

ARTURO BEJAR: Well, suddenly, like, the word "emotion" and the word "experiment" and all these things became really charged.

JAD: Well, yeah, because people thought that Facebook was manipulating emotion and they were like, "How could they?"

ARTURO BEJAR: Yes, but in our case—in our case, right, and in the work that were talking about right now, all of the work that we do begins with a person asking us for help.

JAD: This was Arturo's most emphatic point. He said it over and over that, you know, Facebook isn't just doing this for fun. People are asking for help. They need help. Which points to one of the biggest challenges of living online, which is that, you know, offline, you know, when we try an engineer trust offline or at least just read one another, we do it in these super subtle ways using eye contact and facial expressions and posture and tone of voice, all this nonverbal stuff. And of course, when we go online, we don't have access to any of that.

ARTURO BEJAR: In the absence of that feedback, how do we communicate? What does communication turn into? I mean, I think about, like, what it means to be in the presence of a friend or a loved one, and how do you build experiences that facilitate that when you cannot be physically together?

JAD: Arturo says that's really all he's up to. He's just trying to nudge people a tiny bit so that their online selves are a little bit closer to how they are offline. And I gotta say if he can do that by engineering a couple of phrases like, "Hey, Robert, would you mind," et cetera, er cetera, well, then I'm all for it.

ROBERT: Why not take the position that to create a company that stands between two people who are interacting, and then giving them boxes and statuses and little—and advertising and so forth. This is not doing a service. This is just—this is a way to wedge yourself into the ordinary business of social intercourse and make money on it.

JAD: No ...

ROBERT: And you're acting like this group of people now is going to try to create the moral equivalent of an actual conversation? First of all, it's probably not engineerable, and second of all, I don't believe that for a moment. All I'm thinking is they're going to just go and figure out other ways in which to make a revenue enhancer.

JAD: No, I don't think it's one or the other. I think they're in it for the money. In fact, if they can figure this out and make the internet universe more conducive to trust and less annoying, it could mean trillions of dollars. So yeah, it's the money, but still that doesn't negate the fact that we have to build these systems, right? That we have to make the internet a little bit better.

ROBERT: That's fine. This idea, however, that you're going to have to coach people into the subtleties of the relationship, "Tell him you're sorry," "Tell him this." You know, here's the formula for this. Here's—he doesn't want—"He did something to you. You need to repair that. Here are the seven ways you might repair that." To do all that?

JAD: I mean, you gotta keep in mind how this thing came about. I mean, they tried to get people to talk to each other. They gave them the blank text box, but nobody used it, right? So they're like, "Okay, let's come up with some stock phrases that yes, are generic." But think about the next step. After you send the message saying, you know, "Jad, I don't like the photo. Please, take it down." Presumably then you and I get into a conversation. Maybe I explain myself. I say, "Oh my God. I'm so sorry. I didn't realize that you didn't like that photo. I just thought, like, that was an amazing night. I just thought that was a great night. I didn't realize you thought you looked [bleep]. So sorry. I'll take it down. It's cool." See, now presumably we're having that conversation as the next step.

ROBERT: Why do you presume that? How many of the birthday cards that you've sent to first cousins have resulted in a conversation?

JAD: Maybe not, but ...

ROBERT: See, that's the thing. Sometimes these things are actually not—they're really the opposite of what you're saying. They're conversation substitutes.

JAD: Maybe. Maybe they're conversation starters.

ROBERT: Maybe that's the deep experiment.

JAD: Are they conversation starters or substitutes? Well, I hope they're conversation starters.

ROBERT: Yeah.

JAD: Because maybe that would be a beginning.

ANDREW ZOLLI: It kind of, in my mind, goes back to, like, the beginning of the automobile age.

JAD: This is how Andrew puts it.

ANDREW ZOLLI: There was a time when automobiles were new and, you know, they didn't have turn signals. The tools they did have—like the horn—didn't necessarily indicate all the things that we use it to indicate. It wasn't clear what the horn was actually there to do. Was it there to say "Hello?" Or is it there to say "Get out of the way?" And over time, we created norms. We created roads with lanes, we created turn signals that are primarily there for other people, so that we can coexist in this great flow without crashing into each other.

JAD: And we still have road rage.

ANDREW ZOLLI: And we still have road rage. We still have places where those tools are incomplete.

JAD: Coming up, we wonder if everything—and I mean everything—in the world is not the physical, hard, soft, fuzzy, poke-y stuff that we perceived to be, but actually [sighs] just math. That's coming up.

JAD: Let's just start it up.

ROBERT: Okay.

JAD: I'm Jad Abumrad.

ROBERT: I'm Robert Krulwich.

JAD: This is Radiolab. And today we're gonna continue the conversation we were just having about measurements and how to size things up and the standards by which we do that. But we're gonna shift to math.

ROBERT: Yeah. Now a while ago, I got into a small kerfuffle with a fellow who's completely fascinated by the idea of sizing things up so much, he actually believes that all there is in the world—that is, everything that we can see and feel and touch—those are not real things. They aren't solid like you think them to be. What they simply are are mathematical equations. "Pbbbt!" I thought to myself.

JAD: But science might back him up.

ROBERT: Yeah. His name is Jim Holt.

JIM HOLT: Okay.

ROBERT: And he wrote this really good book called, Why Does the World Exist? And just to get us started, in that book he quotes a poem.

JIM HOLT: Yeah.

ROBERT: Remember the line?

JIM HOLT: Yeah. "Kick at the rock, Sam Johnson, break your bones. But cloudy cloudy is the stuff of stones."

ROBERT: Cloudy cloudy is the stuff of stones.

JIM HOLT: Yeah.

ROBERT: Meaning what?

JIM HOLT: It's something—well, Samuel Johnson, who lived in the 18th century, was a contemporary of Bishop Berkeley. And Bishop Berkeley was an idealist. He believed that the world was essentially pure appearance. It was like a thought, not like a solid reality. It was a thought in the mind of God.

ROBERT: Like the rock really had no substance.

JIM HOLT: And Samuel Johnson, when he heard this, he thought it was ridiculous, and he went and kicked a stone and said, "I refute Berkeley thus."

ROBERT: [laughs]

JIM HOLT: Anyway, that's the story.

JAD: Wait, one guy thought it was a thought, the other guy thought the rock was a—what are they arguing about exactly?

ROBERT: Well, they're arguing about reality.

JIM HOLT: Just what is this world? What is its, you know, essential nature?

ROBERT: When you hold a rock in your hand, like, what's it made of?

JAD: What's it made of?

ROBERT: Yeah.

JAD: Minerals?

ROBERT: No. What I'm really asking is: what is the most essential nature of the rock? So if you look deep, deep, deep down into the rock, do you find something concrete? Do you find a little bit of thing?

JAD: Yeah?

ROBERT: Or do you find something more ethereal, something you can't touch? Something you can't pin down? Something like, oh, a thought. This is Jim's notion.

JIM HOLT: And this sounds like a—it sounds like I'd been eating lotus leaves, but this is what science has increasingly led us to.

JAD: That rocks are thoughts?

ROBERT: Well, to follow Jim's logic, he goes all the way back to the Greeks, to the first real attempt to get to what's really at the bottom of a rock.

JIM HOLT: You know, even in ancient times, the atomist Democritus and Leucippus thought that if you keep cutting up the stuff of reality that we see around us: tables and chairs and rocks and so forth, eventually you cut them up into such itty-bitty pieces that you can't cut any further and then you've got atoms. So there you've got—you've clearly got a fundamental stuff, the atom.

ROBERT: Yeah, that sounds very pleasing.

JIM HOLT: Right. But even going back to Newton, there were reasons to suspect that there was something a little funny about reality. It wasn't quite as substantial as we believed. You know, Newton, of course, came up with a theory of gravity. And the theory of gravity says if you've got the Sun and a planet, the sun exerts a gravitational force on the planet.

ROBERT: Right.

JIM HOLT: And Newton's contemporaries wanted to know ...

ROBERT: Well, how does it do that?

JIM HOLT: What is the mechanism by which gravity is mediated? How does the Sun, as it were, reach out to the Earth, and force it to move around in this orbit?

ROBERT: So if I were an atomist, if I were looking for stuff, then I'd need some kind of thing that carried gravity.

JIM HOLT: Yeah, yeah. But the problem is that it looks like there's nothing between the Earth and Sun except a void.

ROBERT: All that Newton had to fill that void was a mathematical equation that told him how the Sun and the Earth interact. And the thing is it worked. You could plug in the numbers and you could know how one was influencing the other, but Newton had no idea at all why the equation worked. He couldn't point to any, like, a little particle thing like a graviton and say, "There's your reason." It almost seemed like gravity was created from the equation itself, and this disturbed a lot of people, because at that time everybody thought ...

JIM HOLT: That nature has to be made out of hard, durable stuff.

ROBERT: You know, gears and sprockets.

JIM HOLT: Pushing and pulling. That's the essence of reality. And then in the 20th century, of course, it had gotten much much worse. You know, the atom, which was thought to be very, very tiny and you couldn't cut it any further, it was the limit to this, you know, splitting process.

ROBERT: Right.

JIM HOLT: And as we know all too well from the 20th century, you can split an atom. Yeah, and it has pretty interesting consequences. But we also discover the atom is almost entirely empty space. If you took a baseball and put it in the middle of Madison Square Garden, that would be like the nucleus, and the first level of electrons are as far away as the exterior of the Garden.

ROBERT: So you can think of this baseball, this nucleus, as a tiny tot all alone.

JIM HOLT: So it's basically—the atom is a big empty space.

ROBERT: Well, it doesn't feel that way. Like, watch this. I'm going to do this. [claps hands]. Right? [claps hands] If my hands are all atoms, and as you say, atoms are mostly empty space, then why don't my hands just go right through each other like two clouds? But you'll notice ... [claps hands]

JIM HOLT: Yeah, yeah. Why don't I fall through the floor here because the floor is mostly empty space, and I'm mostly empty space? That too, if you look at it in the micro-level, this apparent solidity is the product of a purely mathematical relation.

ROBERT: Well, that can't—isn't it more like my electrons don't like similar electrons? So the electrons on my hands just hate the electrons on the other hand?

JIM HOLT: No, it basically comes down to a pair of mathematical relations: the Pauli exclusion principle and the Heisenberg uncertainty principle. I mean, all of this gets very abstract ...

ROBERT: I understand it perfectly, of course, but I don't want to bore you with the details of his argument.

JAD: [laughs] You have no idea what he's saying, do you?

ROBERT: [laughs] Well, I'll say this: according to Jim, it's not that the electrons in my left hand are repelling the electrons in my right hand. It has to do with a law of nature that says two particles, identical particles, cannot be in the same place at the same time. So when you hear that sound, [claps hands] you can hear it as the sound of a law saying, "No! Not allowed! Not in nature!"

JIM HOLT: Exactly. And here's a slightly different way of putting that.

ROBERT: But wait, isn't this law that we are announcing, isn't this law about particles? Like, we're talking about atoms and electrons. Those are things. So we're still talking about things.

JIM HOLT: If you study quantum field theory, which is what all physics graduate students begin with in graduate school, you discover that even particles are unreal.

ROBERT: [laughs] Oh God!

JIM HOLT: They're just temporary properties of what are called "fields." And fields are just distributions of mathematical quantities through space-time. So they're not—they don't seem to be grounded in anything.

ROBERT: According to Jim, a field is kind of like a stream of numbers.

JIM HOLT: Pure information.

ROBERT: Numbers that tell you where a particle like an electron might be. So maybe the electron's over here. Oh, no, no. Maybe it's over there. Or maybe it's with this group. Or maybe it's with that group. The problem is, you can't ever see the thing itself, you can only see the effect it has on other things. So you can't observe it.

JIM HOLT: And if something is in principle unobservable, you may as well say it doesn't exist.

JAD: Wait a second. No. No, no.

ROBERT: What?

JAD: I mean, I'm on his side, but you could say that it's just not observable down there at the micro-scale. Up here, it's pretty observable. I mean, [bangs table] this table exists. [bangs mixer] This mixer. I mean, something is happening to give the world substance.

ROBERT: Well, according to Jim, what we think happens—and this is admittedly is a gross oversimplification. But in these fields, you're gonna get these little fluctuations, these little ...

JIM HOLT: Events.

ROBERT: Sudden hiccups of energy. Little bursts. And that's where stuffiness flickers into existence. But it's a very flickering existence. Stuff isn't permanent.

JIM HOLT: So what is a rock? I mean, a rock looks like a good, solid, persisting object, but it's really—our perception of it is energy transitions, changes in the distribution of energy from one state to another. When that happens, the energy is irradiated. It goes through my retina. It goes through my pupil, rather, and strikes my retina, and I perceive the rock.

ROBERT: So going back to that poem we started with, I don't know if Jim would call a rock, like Bishop Berkeley did, a thought in the mind of God, but he might say that deep down what a rock is is an expression of rules or math, it's just here like a shadow of an idea.

JIM HOLT: Yeah. Yeah. I've heard one physicist say that the cosmos is ultimately a concept.

ROBERT: Are you increasingly convinced that the reason you can clap, the reason you don't fall through the floor, the reason that gravity works is all because of certain ideas that govern? Ideas rule the world?

JIM HOLT: Yeah. Yeah. Maybe, you know, a hundred years from now when string theory has finally worked out, we might have a very different conception of it. But it looks as though it's going to be mathematics and structure all the way down.

ROBERT: You're okay with this?

JIM HOLT: I like the idea that reality consists—it's a flux of pure information with no further substance.

ROBERT: I don't know why this makes you so happy. I mean, here: I would love if I'm clapping or if I'm hitting someone in the face, I would love to think the billiard ball of me is hitting the billiard ball of them, and that explains what's going on. Now you've offered ...

JIM HOLT: But we're living in almost a spiritual realm. You want to live in this—in this gross material realm, where there's a lot of stuff.

ROBERT: Yeah, but your spiritual realm, it's literally empty. It feels so intuitively wrong.

JIM HOLT: But if you go back to the old 19th-century view, that were made up of these little hard particle atoms that are all bumping around, is it any more plausible that you and I are just a bunch of dumb, hard particles in a certain configuration? And if that's true, you know, how are certain configurations of these particles tantamount to the horrible feeling of pain?

ROBERT: You could say pain, oh, that's ...

JIM HOLT: ... just a lot of elementary particles in a certain configuration.

ROBERT: But we all know that explanation isn't enough. So when you look down to the bottom of everything ...

JIM HOLT: Whether it's a mathematical object, or whether it's little billiard balls knocking around, it's still miraculous and probable that it should produce subjective experience, that it should produce, you know, pleasure and pain.

ROBERT: And that mystery, how you go from the most basic things, or actually, the most basic nothings to everything we see around us ...

JIM HOLT: I find that to be exhilarating. To worry about, you know, the metaphysics of physics, and the nature of reality, even though it doesn't lead you to any sort of comfortable intellectual closure, it makes for—it's a good way of idling away an otherwise boring afternoon, as we've just proved.

ROBERT: [laughs]

JAD: I'm Jad Abumrad.

ROBERT: I'm Robert Krulwich.

JAD: Thanks for listening. And existing.

ROBERT: Temporarily.

[LISTENER: This is Norma from Tampa. Radiolab is supported in part by the Alfred P. Sloan Foundation, enhancing public understanding of science and technology in the modern world. More information about Sloan at www.sloan.org. Radiolab is produced by WNYC and distributed by NPR. Thanks, Radiolab!]

 

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