Instant Genius - Can we really predict when doomsday will happen? – William Poundstone

Episode Date: June 5, 2019

In this episode of the Science Focus Podcast, we’re going to try to guess when the end of the world will happen. Don’t worry, it’s not as gloomy as it might sound. Those people waving ‘The End is Nigh!’ placards are probably completely wrong about an immanent doomsday… Probably. There is a formula that has circulated for the last 50 years which suggests we can pinpoint the end of something with a reasonable amount of certainty. It has been used to predict any number of things, including successful stock market investments, the run of Broadway shows and even how many Harry Potter books go missing from local libraries. But since the 1990s, it has sparked considerable debate among theorists about when humanity as we know it will come to an end. We ask William Poundstone - whose new book How To Predict Everything (£12.99, Oneworld) explains the history of this enigmatic equation - how long we have left as a species on this planet, whether we can shift the odds in our favour, and how we can predict, well, pretty much everything else. How long do you think we have left, and why? Let us know on Twitter at @sciencefocus, and don’t forget to rate and review us wherever you listen to your podcasts. Listen to more episodes of the Science Focus Podcast: What if the Earth’s magnetic field died? – Jim Al-Khalili How can we save our planet? – Sir David Attenborough There is no Plan B for planet Earth – Lord Martin Rees The future of humanity – Michio Kaku Are we facing an insect apocalypse? – Brad Lister This is how to invent everything – Ryan North Follow Science Focus on Twitter, Facebook, Instagram and Hosted on Acast. See acast.com/privacy for more information. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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It means that we have to be a lot more careful in the future to take care of ourselves, to do what's needed to keep this planet viable. And really, this should not be a cause for despair. It should be really a wake-up call. You're listening to the Science Focus podcast from the BBC Science Focus magazine team, with the UK's best-selling science and technology monthly, available in print and in several digital formats throughout the world.

Find out more at ScienceFocus.com. We'll look out for us in your app store. Hello, I'm Jason Gozier, commissioning editor of BBC Science Focus magazine. And this week, we're going to try to guess when the end of the world will happen. But don't worry, it's not as gloomy as it might sound. Those people waving the End-I-Plancaids are completely wrong about an imminent doomsday.

Probably. There's a formula that is circulated for the last 50 years which suggests that we can pinpoint the end of something with a reasonable amount of certainty. It's been used to predict any number of things, including successful stock market investments, the run of Broadway shows, and even how many Harry Potter books go missing from local libraries.

But since the 90s, it sparked considerable debate among theorists about when humanity, as we know, night will come to an end. In this week's Science Focus podcast, we speak to William Poundstone, whose new book, How to Predict Everything, explains the history of this enigmatic equation. We ask him how long we have left with the species on this planet, whether we can shift the odds in our favour, and how we can predict pretty much anything else. He speaks to online editor, Alexander McNamara. So the book is called How to Predict Everything, that's a very, you know, very broad and big subject.

I'm just wondering if you'd be able to explain to us, what exactly is going on? And it sounds like a silly thing to say about how do we predict everything? Well, I've found that, I mean, I've written a number of popular science books before, and I've found that a good way to get a topic is to find a particular subject on which very smart people disagree. So in this book, I'm really writing about one of the big, feuds in the contemporary philosophy of science. It's something called the doomsday argument.

And I took the title, How to Predict Everything from an early article about it, which actually appeared in the New Yorker magazine, which was a profile of one of the originators, Jay Richard Gott the third, a Princeton astrophysicist, who had devised a formula for predicting the future, you might say. So obviously, you know, in the popular magazine, it was called How to Predict Everything. Now, to explain what this doomsday argument is, I found that the best elevator pitch for it is basically like this. Suppose that you buy a lottery ticket, and it's ticket number 62. And you're trying to estimate what's your chance of winning that lottery. Well, you might think on the one hand that, you know, 62's just a number. It doesn't.

doesn't tell you anything. But I think most of us would agree that it does give you some clues. If your lottery ticket is number 62, that basically tells you that there were probably at least 61 other lottery tickets that they printed and sold. So that means your chance of winning is no greater than one over 62. But it also tells you a little more than that. It would be kind of a weird coincidence if your lottery ticket was actually the highest number of all of them. Most likely, it's not. Most likely, you know, there are numbers well, well beyond 62. So if you were to ask, you know, do you think there are a million tickets in this lottery? You would probably say no, because, you know, the chance of having such a low number is 62. If there were actually a million

lottery tickets out there is pretty small. So I think most of us would agree with. with this and would even classify it as common sense. And if you're more mathematically inclined, you might recognize this as an application of Bayes theorem, which is named after Thomas Bayes, an 18th century British preacher who came up with a formula that's now one of the foundations of probability theory. Well, what J. Richard Gott did, and also another astrophysicist named Brandon Carter, is that they realized that... that we can turn our attention to another lottery, one with much bigger stakes. And that's the one that we're all in as members of the human race.

That is to say, the human race had a beginning and presumably someday it will have an end. And suppose we're curious as to when that end might come. Well, demographers have estimated what's called the cumulative population of the human race. Now, this is the total headcount of everyone who has ever lived from the first humans up to right today. And the estimates are generally around 100 billion, which is a pretty amazing number when you think about it, because, you know, there's 7 billion people around right now. So they're really saying that about 7% of all the people who ever lived are living right now. Okay, so that tells us that basically we have drawn the lottery.

ticket number 100 billion in the human lottery. And we want to know how many more humans are going to be born in the future. Well, it would be very unusual, let's say, if we were Adam and Eve, and we're literally the first two humans, because that would be a very, you know, improbable distinction. And it would also be improbable if we were living like five minutes before doomsday, because that would be a weird coincidence that we're doing this podcast about Doomsday, and then it happens during the podcast, you know. So if you use some of this Bayesian math, you can come up with estimates using this demographic information. And one of the things they find is that you can estimate there's a 50% chance that the end of the human race will occur within the next 760 years.

Now, this is, you know, it's not in our time, but still it's pretty close. It's in contrast with what a lot of people tend to assume. So that's why this has become a huge, huge controversy with smart people on both sides of it. And in the book, I kind of do a social history of this going into all the ramifications. And I certainly have a lot of fun writing the book, and I hope that comes through as people read it. It seems like 700 years does seem like quite a long way in the future, but I guess over the course of our existence as a species, that's not too far away, is it?

No, it certainly isn't. In fact, I'm kind of surprised, you know, over the past two years when I've been writing this book, I'm asked to explain this at the dinner table, and when I give that 760 years figure, I'm surprised at how many people say, oh, well, that's not too bad. It's not me.

It's not my grandchildren, you know. So they kind of take it in stride. But you're absolutely right. That is a very small amount of time compared to our species history. So it is a very intriguing claim and has gotten a lot of attention because of that. So you say there's a 50% chance that was that in 760 years, that's when it'll end or it will end by 760 years? He's saying a 50% chance within the next 760 years. And there's also a 50% chance it will be.

be beyond that. And what they get, I mean, when you say they're predicting the end of the human race, it's not like Nostradamus, it's not like the Mayan calendar thing where you have an exact date. It's a probability distribution. And you can give other statistics for it. One of them, you can say there's a 95% chance that doomsday will occur anywhere from 20 to 30,000 years from now. So that's a wider range, but you have much greater confidence that it's going to occur in that range. And again, this is still, even 30,000 years is a pretty small time compared to the history of the human race. So obviously 20 years is a lot sooner than that. And then so sort of coming back to that lottery ticket analogy, if we pulled out the 60 second ticket or I think it was,

that would essentially be us at that end, which would be beyond the 95, the 30,000 years as well. So that's kind of, it seems unlikely in general that we're at that point. Yeah, it's unlikely that we're right before Doomsday, and it's unlikely that we're very, very early in the human race. Again, it's a broad order of magnitude estimate using this Bayesian math, which is, you know, accepted in many other contexts. But I think one of the reasons that people find it so challenging is that we do have this cultural expectation that the human race is going to survive a very long time. I mean, we've seen it in the movies. We've seen it in the Star Trek and so forth that we're going to go out and explore the galaxy, have huge populations on other planets. But God is saying, you know, don't be too sure of that.

If we just look at the statistical evidence we've got right now, it would seem that's very, very improper. And is that why it's so controversial? Yeah, I think that's definitely part of it. I mean, God has used this to predict, as I say, everything. He has predicted the runs of Broadway plays. He's predicted how long monuments will stand. His first prediction, actually, when he was a grad student, he took a tour to Europe. He went to Stonehead.

He went to the Berlin Wall. And when he was at the Berlin Wall, he made a prediction that, there was a 50% chance that it would stand for anywhere from 2.7 years to 24 years from that time. It was 1969. And of course, it was actually torn down in 22 years after that prediction. So that was the first one that came true. And he said to himself, you know, maybe I should write this down. Maybe I should write this down. So he ended up publishing it in nature. And that's really what started this whole conversation about. Is this valid or not?

So would you be able to sort of explain the logic behind, you know, here's calculation there? Yeah. Basically, imagine that you had a list of all the human beings, by name, listed in chronological order. So we'd start with Adam and Eve or whoever you'd want to call the first earliest humans. It would go through people in the present day, including you and me. It would go into the future, having all the future people. So this list would have to be a book, I guess, a very thick book with very fine print. But, okay, suppose we're asking you to guess, where are you in this book?

Where is your name in this book? And the answer is, presumably we don't have any idea. It could be that the human race is going to last a very long time, have huge populations in the future, in which case we could be very early in that book. Conversely, it could be that we're very near the end, and it is going to be five minutes from now, in which case we'd be practically on the last page of that book. But the point is we really don't know. So the fact that we're so ignorant about our relative position in time allows us to make some probability statements about it.

We can say that there's a 50% chance that my name is in the first half, of that book and a 50% chance it's in the last half of that book. And we can likewise say that there's like a 95% chance that I'm in the middle 95% of that book. In other words, I'm not in the very first few pages of it and I'm not in the very few last pages of it. So if you do that, you get these predictions that God has been producing. And if people have say, well, that doesn't sound reasonable. You can actually make very similar predictions with a phone book. You can say, okay, there's a 50% chance that your name is in the first half of the phone book and a 50% chance. It's in the second half. Most people would say that makes sense, you know. You can also say there's a 95% chance that

you're in the middle, 95% of the phone book. Well, my name is, I'm poundstone. It begins with a P. So yeah, that's in the middle of the phone book. And, of course, there are some people who are in the very beginning of the phone book, and some people are in the very end. For them, the prediction will be wrong, but it is a probabilistic prediction. And for 95% of the people, that prediction is going to be right. So what God is saying is that based on the statistics, half the population, half of the ultimate population of the human race is going to find that they're within, 760 years of Doomsday. So that's basically the basis of that.

So obviously that works if we've got a list of everyone who was, is, and will be. But what happens if we don't have, you know, a list of everyone's names into the future? Yes, that's a good point, and that's one of the arguments that has been advanced against it. And there are counter arguments to that. The philosopher John Leslie has one where he, I asked you to imagine that there's some sort of foundation that is awarding valuable emeralds to people. And it's got 5,0003 emeralds. And it's going to give them three emeralds to randomly chosen people in one century,

and then 5,000 emeralds to 5,000 randomly chosen people in a later century. Now, suppose you're one of the people who receives one of these emeralds. and you have a vow of secrecy, you can't reveal that you want it, you don't know anyone else who has wanted. The odds are that you're going to be one of the 5,000 people in the later century, because obviously there's far more people getting it in that later century than just the three who are getting it in the earlier century. But obviously the foundation, you know, it will have a list with 5,0003 blanks, on it. If you're in the early century, it's only filled out the first three names. The other 5,000 are blank because they haven't even been born yet. Yet, even so, the statistics still apply.

If you get an emerald, chances are you're in the later century. So you don't have to have a complete list right now in order to make this Bayesian math, is what he's saying. It is quite a complicated thing sort of get your head around as it were. Yes, exactly. Yeah. And so obviously there's a lot of a lot of the debate from the book, it seems that a lot of the debate has been, you know, people have been saying one thing and it's been counter arguments and counter arguments. Is this still running on? Is this still like this debate still happening?

Yes, exactly. I mean, it's produced, I think, about 83. academic papers I've counted, including several in the past year. So it's still very much a very big topic in contemporary philosophy. I suppose one of the things that you could sort of have a guess at now is to see how predict how much further it's going to go on based on those 83 papers. Well, yeah, if you did that, the fact that it's been running since, I guess it's 1993, so that's 26 years. You would say that, you know, the median estimate would be at least 26 more years. So obviously, this is, you know, this is all statistics and probabilities of

things that are likely to happen. Obviously, a lot of what it talks about is Doomsday, which is the end of civilization. But on a more practical level, how is this, how are we using this to sort of not necessarily influence our lives, but using it in a way that is actually useful for us? Yes. Gott has found that it applies to really all sorts of things. He began predicting the runs of Broadway plays. On the date that his paper in Nature was published back in 1993, he looked at all the plays that were then running on Broadway. And he looked at how long they had been running then. And he used the same math to predict. give a probability distribution of how long they would run in the future.

And this was plays like the original run of, or the original Broadway run of cats, as well as many obscure plays. And he found that they fit his statistical predictions very closely. And this has been applied to even things like the number of Harry Potter books being stolen in the San Diego Public Library. But one of the more interesting things about it that has gotten a lot of attention from economists is that it seems to apply to the survival and profitability of corporations. If you look at how long a company has existed or how long it has been on an index,

like in the U.S. we have what's called the Standard and Poor's 500. the doomsday style reasoning is actually a very accurate way of predicting how long that company will remain in business and how long it will remain on that index. So this has some significance. What it really tells us is that if you're trying to estimate how much a particular stock should be worth, you have to look at what its future earnings will be. And of course, obviously, how long it's. stays in business is a very important determinant of that. And this seems to say that it makes a lot

of sense to buy companies that have been around a long time, like maybe Coca-Cola, as opposed to companies that have just now come into existence or fairly new, like maybe Tesla. And it's provocative because this is sort of the opposite of the way that an awful lot of people try to invest in the stock market. They look for new, exciting companies that have an interesting story that seem to represent the future. And they don't try to, they pay less attention to companies like Coca-Cola or Heinz or General Motors that have been around a long time and, you know, have a very stable business, a long history of dividends and interest in everything. But there's reason to believe that you would, on average, do better by picking some of these companies that have been around a long time

because that says they'll be around in the future. And if you look at the way that Warren Buffett has invested, he actually seems to implement this idea of favoring companies with a very long history of earnings and being in existence. And so this, obviously, this theory is practical in so many, many places here that we've already seen it with, you know, library books, as you say, to big financial things like that. And I guess obviously there are, as we learn to understand it more, we can use it in other practical, not practical, but other situations as well. Like in, you know, maybe in scientific research or, you know, looking out to space and that sort of thing. Yeah, exactly. And as I say, I think it's really because we, we just have this very emotional

reaction to the idea that the human race itself is mortal. And, you know, know, has a finite amount of time, that we accept this with things like companies or Broadway plays. But when you talk about the human future, I think it gets a lot of people's hackles up. Yeah, I can imagine, like, with our future. Now, there's obviously things that happen in our future that, you know, we have some control about, like you mentioned earlier, like going to space. And that's something, you know, like the Star Trek style reaching out all over the universe and everything like that. Are there some sort of implications that can be done?

If we do make it out into space and populate another planet, are we then sort of reassessing our boundaries of what we call the human race or maybe even just as we maybe sometime in the future we evolve into a different species? Like where does that fit into it? Well, that's another issue. I mean, it may well be that we will evolve into a different species. And there's some controversy about how, you figure that. If we're saying that in 760 years, the human race is gone, but maybe we

evolve through technology into something quite different, maybe that's sort of an escape clause. And some people feel that maybe it is. But as to the idea of going into space, this is actually something that God supports. He believes that this would help our chances of going beyond this the 760 years or so. And in fact, in his original nature paper, where he described the doomsday argument, he also provided an explanation of what's known as the Fermi question. Now, this is named for the great physicist, Enrico Fermi, who way back in 1960 asked, where is everybody?

Now, he was talking about extraterrestrial beings. At that point, there had been some reports of flying solaceous. And he was kind of joking about that. But no one really believed that the flying saucers were extraterrestrials. But he was aware that, you know, there's an awful lot of planets and stars in our galaxy. And if life evolves the way we think it does, there should really be thousands or even millions of other intelligent species just in our galaxy. And obviously some of them would be millions or even billions of years ahead of us. So you expect them to have incredibly advanced technology.

They would be coming here, and we should have seen evidence of them, except, of course, that we don't. And ever since that time, you know, a lot of people have wondered, why don't we see evidence of extraterrestrial life? We've done these search for extraterrestrial intelligence efforts where we have radio telescopes listening for very faint signals. And no one has ever found anything that's convincingly a signal of extraterrestrial intelligence. life. Well, God's explanation for that is kind of similar to the doomsday reasoning. He's assuming that maybe ETs are not necessarily that different from ourselves. In other words, if you ask why aren't ETs visiting us in their spaceships, well, God would have us ask, why aren't we visiting ETs in our own spaceships? And the answer is, well, we haven't

develop the technology yet. We expect to develop it someday, but we haven't done it yet. And God is saying maybe that's a pretty typical state of affairs for an intelligent being in our galaxy. It could be that a lot of species develop technology. They go through a population boom. They have all these great plans that they tend to realize, but then for some reason or other, their civilization ends, and they never get around realizing all these things that maybe they were smart enough to do, but they just never had the time to do it. So God certainly isn't saying that there aren't extraterrestrial beings out there, but he's saying that either they're less common than we think, or they may not have as long as we tend to imagine in these typical Star Trek-type

fantasies to really develop their technology and explore the whole galaxy. So in his view, the answer to the Fermi question may be that there's just fewer really technological species out there than we really think. And this is an idea that's been extended just in the past year by a group at the Oxford think tank, the Future of Humanity Institute. they did a statistical study where they looked at all the estimates that people have provided for what's known as the Drake equation after Frank Drake, who was the first astronomer to really search for extraterrestrial signals. And Drake argued that you could estimate the number of extraterrestrial species in the galaxy from seven factors, basically.

You have to look at how many stars come up. into existence each year in the galaxy. How many have planets? How many of those planets develop life? How many develop intelligent life? How many develop, say, radio or interstellar technology? And finally, the average lifetime of those technological species. Now, it was at the time when Drake proposed this, it was hard to estimate all of these seven

factors. More recently, of course, we've discovered all these planets. around other stars. And some of these factors we can now estimate pretty accurately. But we still don't know things like what's the average lifetime of a communicating species. So this Oxford group, they looked at all the estimates that have been proposed for these seven factors in the literature and then put them into some software, which basically, you know, randomly selected estimates and multiplied them together as required by this equation to come up with different estimates of the total number of species in our galaxy.

And what they found is that, you know, we realize there's uncertainties in these seven figures, but what we don't realize is that you're not just multiplying the factors, you're also multiplying the uncertainties in these factors. And when you have several very, very uncertain factors, this leads to huge uncertainties in the final estimate. So what they found was that if you took the average estimates, the median estimate of all the estimates was about 50 million extraterrestrial species in our galaxy. But at the same time, they found that there was a one-third chance that you would find that there were no extraterrestrials at all in our galaxy.

Now, this is a type of statistics that's very hard for people to wrap their heads around. A good way of explaining it is that it's something like income inequality. If you go to a city like London or Manhattan, the average wealth is very high because you've got a few billionaires pulling up that average. But still, the first person you pass in the street is a pretty good chance that he could be a very poor person because there is this huge statistical skew in the figures. And that's what we're finding with Drake estimates. Although typical Drake estimates have very, very many extraterrestrials in our galaxy, about a third of them have basically zero. So there's really no reason to be amazed if we find that there seem to be no extraterrestrials in our galaxy.

It could be that we just are at that one end of the probability distribution, and there really aren't any out there. And that sort of comes back to the original sort of doomsday calculation, just the image that I have of that way, you know, it's unlikely that you're one side or the other, so it could well be somewhere in the middle. There's a lot to sort of get your head around in that. But, you know, one thing I thought about there was the fact that humans have been around for, what, 200,000 years, I think, roughly. Yeah, 200,000. And, but we've only been sending messages that, you know, into space for the last 100, essentially. So that's a very short window. And anyone, you know, we could be on the brink of nuclear war in the next 10, 20 years or whatever.

which would mean that there'd be a very short window. I guess that's sort of facted into the fact that there might be intelligent species out there as well. Yes, exactly. And not just that. It may be that in 100 years we'll invent something that's so much better than radio waves that we stop using radio waves and use that. But since we haven't invented it here on Earth, we can't pick it up, you know. Yeah, okay.

And so extraterrestrials might be using that one, and we just haven't worked that out yet. Yeah. So, I mean, it's just, it's incredible, just. how much it sort of takes into account just this whole, this whole theory, as it were. And obviously, you've used quite a few examples of how to sort of explain it already, but in the book it's filled with these wonderful sort of thought experiments. Do you have any sort of, are there any of those sorts of experiments in the book, which is a particular favourite of yours, or one that, you know, you really like to say, this is a great

explaining. One that's certainly gotten a lot of attention is known as the shooting room. This was devised by the philosopher John Leslie, who is one of the ones who has written probably two dozen papers on the doomsday argument and has really been someone who has been with this debate from the beginning. And he said it literally made him physically ill. Just he would be in bed at night, trying to think of ways of proving or disproving the doomsday argument. And he was just obsessed with it. But one of the things he came up with was this shooting room thought experiment. So imagine that you're led into this room called the shooting room.

And the way it works, there's a guy there, call him the commandant. And he's going to roll two dice. If the two dice come up six, then he tells a firing squad to shoot you. But if they don't come up double sixes, then you're free. So if you've got like a one in 36 chance. of being killed. So your chances are pretty good of surviving. But if you do survive, what happens is that you leave the room and then nine new people come in. And it's the same deal again. The commandant rolls two dice. If they come up double sixes, they shoot everyone, but otherwise all nine are released.

And if those nine are released, then 90 people, new people come in. And the number keeps increasing by a factor of 10 each time that the commandant rolls something other than two sixes. Now, this has an unusual feature. Suppose you're trying to figure out what's the chance if I'm in this room that I'm going to get killed. Well, as I said, the most obvious answer is 136, because that's the chance of rolling double sixes. But look at it this way. the rules are arranged so that whenever so that when you do actually so when the commandant

finally rolls those double sixes as he must eventually the number of people in the room then is going to be 90% of all those who were ever in the room in other words if if it happens on the on the second time there's there's nine people in the room you're the one who got out on the first round, then 90% of the 10 who were in the room have been killed. So it looks like you can claim that your chances of being killed in this room are 90%. So which is it? 90% or 16%. Now, Leslie came up with this because it really is a lot like the doomsday argument. The reason where we get these figures is because, you know, the human population has

increased geometrically, basically since the invention of agriculture. So as I said, about 7% of the people who have ever lived are living right now. And you find that, you know, when doomsday does come, a disproportionately large amount of the human race is going to exist in the years relatively close to doomsday. So it's really the same sort of situation in a way that hopefully makes it a little easier to understand, although not everyone's convinced it does. No, that certainly puts it, you know, gives that vast range of uncertainty at the same time, sort of making it seem clear as to what's happening at the end, ultimately.

Yeah. It is all about doomsday, and, you know, how long we've got left on this planet as we are. Ultimately, can we use this equation to sort of say, are we doomed, basically? Well, I think it's, Leslie likes to think of it is that it should be regarded as a wake-up call. What we're saying is that based on the statistics that we currently have right now, it looks like our future may not be as long as we think. But that doesn't mean we have to settle for that. It means that we have to be a lot more careful in the future to take care of ourselves, to do what's needed to keep the planet viable. And really, this should not be a cause for despair. It should be really a wake-up call.

That was William Poundstone, whose new book, How to Predict Everything, is out now. How long do you think we have left and why? Let us know on Twitter at at Science Focus. And don't forget to rate and reviewers wherever you listen to your podcasts. If you see your immediate future filled with the latest science and tech, the latest issue of BBC Science Focus is packed full of features, news and interviews to help you make sense of the world around you. In the June 2019 issue, we go on the hunt for pains on-off switch, discover the clever creatures using tools to eat food, and ask, is there really life on Mars? Thank you for listening to the Science Focus podcast from the BBC Science Focus magazine team. With the UK's best-selling sites and technology monthly, available in

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