Why Are We Here? Physics Has Answers

IRA: This is Science Friday, I’m Ira Flatow. Why are we here, or rather, how? The answer of course, will depend on whom you ask. A biologist would give you one answer, ask a physicist though, and you might hear something about the Higgs boson. How it gives us mass under the standard model of physics.

My next guest thinks a lot about how the universe came to be and how it might end. And we still don’t know about both of these questions. Lawrence Krauss is a theoretical physicist and director of the Origins Project at Arizona State University in Tempe, Arizona. He is author of the greatest story ever told so far. Out at the end of the month, and he’s an old friend of Science Friday. Welcome back, Lawrence.

LAWRENCE: It’s always good to be back, Ira.

IRA: Thank you, that is a provocative title, especially the– so far. What makes modern physics such a great story so far?

LAWRENCE: Well the point is, it’s the greatest intellectual journey that humans have ever taken. It’s full of surprises, pathos, frustrations, all the aspects that make human stories wonderful. But the really important part, as you just said, is this so far part. Because the greatest part about the greatest story ever told so far, is it’s getting better all the time. The story of science changes, it evolves. It’s not like that other supposed greatest story ever told, so far which is sort of static, and not even that interesting.

IRA: So I think that’s a lot of what people don’t realize. They think when they hear the word science, it’s just an encyclopedic book of everything we know, it’s sitting on the table. But that is not how science works, is it?

LAWRENCE: No, in fact, that’s the key thing. It’s the process of science that’s so important. And what this book is in some sense, is a celebration of that process. How it’s taken us– it starts with Plato, but how it’s taken us the last 500 years from just beginning to learn about the laws of motion to understanding that the universe we see is really an illusion. It’s really a shadow of reality. And the amazing developments that have taken physicists literally kicking and screaming.

Nature dragged us here, it’s not as if it was sort of obvious all the way. There’s lots of red herrings. Too often we present science not only just as a set of facts, instead of a process for deriving those facts, but also of some logical continuum. But it’s really of course, a human activity where oftentimes you can go down a blind alley for an awful long time. Or even have the answer, but not know you have the answer. Which happens, and it happened in the history of particle physics, certainly in the last 50 years.

IRA: You know, and we’ve talked over the years about physics and discoveries, and you’ve said many times that it’s the joy of not knowing. And then that sometimes when physicists find an experiment to be wrong and they don’t find something, they’re not disappointed, they’re even happier.

LAWRENCE: Sometimes in fact, I often say the two best states for at least a theorist to be in are wrong and confused. Because that means there’s more to learn. And often times, in fact, there have been very important experiments have surprised us right back from the Michelson – Morley experiment, where we expected to see the earth moving in the background of the ether.

Experiments surprise us. We expected to see the universe slowing down, and what happened? It was speeding up. And I have to say, even in my case, the experiments surprised us with the Large Hadron Collider. I was betting that the Higgs field didn’t exist, that Dave’s particle wouldn’t be discovered. It just seemed too slippery a solution, even though it was really the centerpiece of the standard model. I thought nature would come up with a different answer, and it didn’t, which certainly surprised me at least.

IRA: So now, does that make you have to re-evaluate your ideas?

LAWRENCE: Of course, and what’s wonderful about that is the minute the Higgs was discovered, I began to think of implications that I’d never thought of before. It’s often as a theoretical physicist, it’s kind of amazing to me how I’ve written papers after the fact, after discovery that I could have anticipated before the discovery. But somehow when it’s real, when the experiment presents it to you, suddenly you start to think of implications in a new way. And that’s really what happened. As I say, we often think of physicists as being– physics as being done by Einstein and other people in a room late at night alone. That’s not the way it’s done, generally.

First of all, it’s a collaborative enterprise. It’s full of lots of individuals. I mean the Large Hadron Collider has 10,000 physicists from over 100 countries, speaking dozens of languages. And like I say, it’s a Gothic cathedral of the 21st century. But it’s also most often, what is healthy anyway, being driven by experiment. The experiment forces us to change our ideas. If you locked theoretical physicists in a room and had them come up with a picture of the universe, the picture they’d come up with wouldn’t look at all like the universe in which we live in.

IRA: Mm-hmm. Our number, if you’d like to join us, Dr. Lawrence Krauss, 844-724-8255, author of The Greatest Story Ever Told So Far. Is there any new physics that needs to be discovered for us to move forward? Of course you’re laughing at that. Even before I finished asking.

LAWRENCE: Well, I think you know the answer, of course. That’s the great thing about science, is each time we make a discovery, there are almost more questions than answers. So we sure– we discovered the Higgs particle. And it told us, it validated a notion which is so amazing, I have to repeat it. It validated that notion that there is an invisible field everywhere in the universe that allows us to exist. Which by the way, sounds religious, doesn’t it? But the difference is that invisible field that we postulated had to be discovered, and that’s what the Large Hadron Collider is about.

But the question now is, so we’ve discovered that that field exists, and we wouldn’t be here if it weren’t for that. The universe certainly isn’t designed for our existence. The fundamental laws in fact, wouldn’t even allow for our existence unless this field had frozen in the earliest history of the universe, and changed the properties of the forces we measure, and the particles that make us up.

But the next question is, why did it freeze? Why is it there? Why did freeze at– have the value it does? Does it indicate something? In fact, the scale that it froze at is a very unusual scale. Because if we think of the three of the four forces nature unify, it would happen in a very different scale. Why are the skills different? There are tons of questions that arise, now that we know what happened. The question I was going to say why it happened, but really the question is how did it happen?

IRA: And you know, since we talked about that discovery, there have been other discoveries. And since the Higgs, and I’m talking now about gravity waves. I mean that really–

LAWRENCE: Of course, gravity– I mean, the discovery of gravity waves is another amazing thing, which by the way, I would never have thought was possible. I mean, that’s the reason I’m a theorist, I suppose. I look at those experiments to measure gravity waves. LIGO had to measure a difference in length between two 4 kilometer long arms as the gravity wave comes by, it would cause the length of the two arms to change a little bit. But the amount to change by is 1/1,000 the size of a proton. I mean, who would have thought you could do that? It’s amazing.

But what’s really neat, is that this just opens up. We’re sort of like Galileo when he turned his telescope up to see the moons of Jupiter. We’re entering a new era of astronomy, gravitational wave astronomy, that’s going to reveal a whole new window on the universe. And every time we open up new windows, we’re surprised. And as far as I’m concerned, probably the most interesting surprise will be when we can measure gravity waves not from colliding black holes as LIGO did, but in fact, gravitational waves that are created at the beginning of time.

Because gravitational waves created in the initial moments of the Big Bang can actually make it here to us through that dense early universe, and we could actually probe a signal from a time when the universe was a billionth of a billionth of a billionth of a billionth of a second old. To test the idea that we’re building upon after the discovery of the Higgs. It will allow us to test not just how the universe began, but actually probe particle physics at a scale that’s probably 12 orders of magnitude higher in energy than we could ever do with accelerators on the ground. You’d have to have an accelerator whose circumference was the earth moon distance in order to probe the same kind of physics that we may probe with gravity waves from the early universe, it’s remarkable.

IRA: It is remarkable. And you know, it’s also a remarkable as you say, you’re a theorist. You don’t build them the equipment, you just go to the blackboard and talk about it.

LAWRENCE: Yeah, I just talk.

IRA: And you leave it up to the engineers, and whatever the guys who make– women who make these devices. To think that you could build– I mean, hearing you talk about the machine, the LIGO itself, how accurate it has to be. That’s almost an amazing event in itself, being able to parade–

LAWRENCE: It’s worth celebrating as part of The Greatest Story Ever Told So Far, it really is a great story. And LIGO is wonderful, but we shouldn’t discount the Large Hadron Collider, which is probably even a more complex system, in a sense that every second, more information is generated in it than in all the world’s libraries. It involves a vacuum tunnel that’s 26 kilometers long, where the vacuum is sparser than the vacuum of empty space. It’s amazing to think that humanity has built these incredible devices just to test these ideas about how we got here and where we come from. Directly, they won’t make a better toaster.

Some people say why is it worth doing that? What will it help us do? And of course, there are side benefits. [? CERN ?] produced ultimately the world wide web, for example, which we all rely on. But it’s not worth funding for those side benefits. It’s really answering those fundamental questions that you, and I, and everyone else has that makes us all scientists, in some sense. Why do we get here? How did we get here? Are we alone? All those interesting questions.

IRA: Are you fearful that some of the funding for basic science may go away? In this new–

LAWRENCE: Oh, absolutely. In the current climate, with the President’s budget that’s just come out, for example, cut fundamental funding for the kind of research I’m talking about by 20%. But it’s not just that, I’m as concerned about the cuts in science as I am about the cuts in the national endowment for the arts and humanities. And of course, relevant for this program, the Corporation for Public Broadcasting. These hit the fundamental aspects of our civilization.

The things that really make us great. There’s a wonderful quote that Robert Wilson, who was the first director of the Fermi national accelerator laboratory, a particle accelerator, when he was talking before Congress, he was asked would it aid in the defense of the nation. And he said no, but it’ll help keep the nation worth defending. And I think that’s really worth remembering today in the current climate.

IRA: Let’s go to the phones, lots of interesting calls. Let’s go to Mike in Houston, hi, Mike.

MIKE: Hey, how’s it going, guys?

IRA: Hi there.

LAWRENCE: Hi.

MIKE: Hey, I just want to make a quick comment about the Higgs boson particle. On the news last year, it was somewhat amusing. They said that in an episode of The Simpsons, Homer Simpson had roughly estimated the size of the Higgs-Boson particle like 10 years ago. Were you aware of that? Did you hear that?

LAWRENCE: No, I didn’t see his paper on the subject, actually.

MIKE: Anyway, I just thought I’d mention that. But secondly, with space travel, we use rocket fuel from the 1950’s. What do you think is the next generation of propulsion systems? And do you think–

[INTERPOSING VOICES]

LAWRENCE: We’re already using them. I think, to jump in. I mean, and Ira may have talked about on this program or others, that we’re using for example, electronic propulsion techniques where we’re basically using electric fields to propel atoms out the back of a spacecraft very fast. What it does, especially for deep space missions, is allows those rockets to move faster than they would with just chemical propulsion. So that’s certainly one of the new propulsion technologies. And as we look to go deeper and deeper in space, certainly conventional rocket fuel become less and less worthwhile. To get us out of the earth, maybe.

IRA: Do you foresee us in the near future being able to successfully unitize gravity with quantum.

LAWRENCE: With the other, right now, we know three of the four forces in nature. We’ve discovered them. And by the way, I will jump in and say often we think of the most exciting decades of the 20th century to be 1905 to 1925, when special general relativity and quantum mechanics were developed. But part of the reason for this book, is there is an unheralded 20 years, 1955 to 1975.

At the beginning of that, we understood one force of nature as a quantum theory, electromagnetism. By 1975, we understood three of the four forces of nature exactly as quantum theories. It was just an amazing development and a revolutionary one, that I think future historians may think is perhaps one of the most revolutionary periods in the 20th century.

But again, right now as you alluded, there’s one force that’s still an outlier, and that’s gravity. We don’t have a quantum theory of gravity. There are ideas of course, and string theory was developed to hopefully produce such a quantum theory. We don’t know if it is, in a sense. We don’t know if– it’s an interesting idea. But we don’t know if it relates to the real world yet. And the answer of course, Ira, is we don’t know. That’s what makes discovery so wonderful. People always ask me, you know, what’s the next big development? Now we say, if I knew, I’d be doing it.

IRA: May I remind everybody that this is Science Friday from PRI, Public Radio International. Talking with Lawrence Krauss, director of the Origins Project at Arizona State University, and author of The Greatest Story Ever Told So Far. Another great book, Lawrence, in the series of books that you have continued to do.

LAWRENCE: I’m very pleased with this book. You know, every book I learn something new, and I’m often surprised. In this case, the story, which I began to delve in, I knew the physics. But the actual history of it turned out to be far more for interesting than I imagined. When you see these people and these great scientists that I discuss, almost getting the right solution 10 or 20 years before it came out, and you just want to shake them and say, just look over here. You’ve got it all right there, it’s kind of amazing. In retrospect of course, things are always clear in hindsight.

IRA: That’s Monday morning quarterbacking, right?

LAWRENCE: Yeah, exactly.

IRA: Let’s go to the phones, see if we can get a couple of calls in here. Let’s go to Damascus, Maryland. Hi, welcome to Science Friday. Patrick.

PATRICK: Hi, thank you for taking my call. So Lawrence, I have a question for you. I had a few, but I think I’ll stick with one. I was wondering if it was in your mind, you felt that it may be a bit of a misnomer to call the laws of physics or nature laws, as opposed to properties.

LAWRENCE: Well, you know, why?

PATRICK: Well, I would say whereas laws feel like they constrain matter and energy, and then properties seems like it emanates from matter and energy.

LAWRENCE: Well–

IRA: Explain what the law of physics is. What does that mean, by law–

LAWRENCE: Well, it’s good. It’s a really good question in general. And a law is basically, it does constrain things. That’s why it’s well named. In physics, we really can’t say what’s possible, we can really say effectively what’s impossible. Because we do experiments that rule out ideas. And even the ideas that survive, may not be all the ideas. So a law of physics is something that basically is a theory that’s been tested by experiment. And a law that we find that every experiment tells us is not violated, and moreover, we have very sound theoretical reasons for understanding.

Let me give you an example. And it’s really important, because it points to some of the ways we don’t teach science correctly in schools. Often, we tell kids well, there’s a law of conservation of energy, and a law of conservation of momentum. And it sounds like that comes from the Ten Commandments, or something. That we just wrote it down and said this is the way it is. But we now understand that these laws derive from fundamental symmetries of nature. The reason energy is conserved, is that’s equivalent to saying the laws of physics don’t change with time, which we measure every day. And it’s really important if laws of physics did change with time, you’d have to take a different introductory physics class every year. And people really hate that.

The law of conservation of momentum comes from the fact that the laws of physics don’t change from point to point. These are fundamental aspects of the universe that are highly unlikely to change. And that’s why we have such great confidence that those laws ultimately do constrain any new theory. And any new theory will have to accommodate those facts. And if it doesn’t, it will have to explain in some sense how the laws of physics change from place to place, or from time to time.

IRA: Lawrence, wish we had more time. Always, always a pleasure to talk to you.

LAWRENCE: It’s always a pleasure to talk to you, Ira. Wish we had more time, too. I’ll come back sometime.

IRA: We’ll have you back. Lawrence Krauss, foundation professor and director of the Origins Project, Arizona State University in Tempe. Author of The Greatest Story Ever Told So Far, out next month on Atria books. Thanks again, have a good weekend Lawrence.

One last thing before we go, a special shout out to our listeners in Florida. Just 11 days, Science Friday will be onstage at the Bob Carr theater in Orlando. We’ll be talking about bionic arms, Navy missile decoys, NASA robots that can mine the moon. And yes, there will be robot demos on stage. I don’t know, maybe we’ll have a battle of the bots. Not promising, but the robots will be there. Who knows what could happen? Tickets are selling fast, so grab yours at sciencefriday.com/orlando. That’s sciencefriday.com/orlando 11 days from now on the stage at the Bob Carr theater in Orlando.

BJ Lederman composed our theme music, our thanks to our production partners at the studios of the City University of New York. Have a great St. Patrick’s Day, happy weekend. We’ll see you next week, I’m Ira Flatow in New York.

IRA: This is Science Friday, I’m Ira Flatow. Why are we here, or rather, how? The answer of course, will depend on whom you ask. A biologist would give you one answer, ask a physicist though, and you might hear something about the Higgs boson. How it gives us mass under the standard model of physics.

My next guest thinks a lot about how the universe came to be and how it might end. And we still don’t know about both of these questions. Lawrence Krauss is a theoretical physicist and director of the Origins Project at Arizona State University in Tempe, Arizona. He is author of the greatest story ever told so far. Out at the end of the month, and he’s an old friend of Science Friday. Welcome back, Lawrence.

LAWRENCE: It’s always good to be back, Ira.

IRA: Thank you, that is a provocative title, especially the– so far. What makes modern physics such a great story so far?

LAWRENCE: Well the point is, it’s the greatest intellectual journey that humans have ever taken. It’s full of surprises, pathos, frustrations, all the aspects that make human stories wonderful. But the really important part, as you just said, is this so far part. Because the greatest part about the greatest story ever told so far, is it’s getting better all the time. The story of science changes, it evolves. It’s not like that other supposed greatest story ever told, so far which is sort of static, and not even that interesting.

IRA: So I think that’s a lot of what people don’t realize. They think when they hear the word science, it’s just an encyclopedic book of everything we know, it’s sitting on the table. But that is not how science works, is it?

LAWRENCE: No, in fact, that’s the key thing. It’s the process of science that’s so important. And what this book is in some sense, is a celebration of that process. How it’s taken us– it starts with Plato, but how it’s taken us the last 500 years from just beginning to learn about the laws of motion to understanding that the universe we see is really an illusion. It’s really a shadow of reality. And the amazing developments that have taken physicists literally kicking and screaming.

Nature dragged us here, it’s not as if it was sort of obvious all the way. There’s lots of red herrings. Too often we present science not only just as a set of facts, instead of a process for deriving those facts, but also of some logical continuum. But it’s really of course, a human activity where oftentimes you can go down a blind alley for an awful long time. Or even have the answer, but not know you have the answer. Which happens, and it happened in the history of particle physics, certainly in the last 50 years.

IRA: You know, and we’ve talked over the years about physics and discoveries, and you’ve said many times that it’s the joy of not knowing. And then that sometimes when physicists find an experiment to be wrong and they don’t find something, they’re not disappointed, they’re even happier.

LAWRENCE: Sometimes in fact, I often say the two best states for at least a theorist to be in are wrong and confused. Because that means there’s more to learn. And often times, in fact, there have been very important experiments have surprised us right back from the Michelson – Morley experiment, where we expected to see the earth moving in the background of the ether.

Experiments surprise us. We expected to see the universe slowing down, and what happened? It was speeding up. And I have to say, even in my case, the experiments surprised us with the Large Hadron Collider. I was betting that the Higgs field didn’t exist, that Dave’s particle wouldn’t be discovered. It just seemed too slippery a solution, even though it was really the centerpiece of the standard model. I thought nature would come up with a different answer, and it didn’t, which certainly surprised me at least.

IRA: So now, does that make you have to re-evaluate your ideas?

LAWRENCE: Of course, and what’s wonderful about that is the minute the Higgs was discovered, I began to think of implications that I’d never thought of before. It’s often as a theoretical physicist, it’s kind of amazing to me how I’ve written papers after the fact, after discovery that I could have anticipated before the discovery. But somehow when it’s real, when the experiment presents it to you, suddenly you start to think of implications in a new way. And that’s really what happened. As I say, we often think of physicists as being– physics as being done by Einstein and other people in a room late at night alone. That’s not the way it’s done, generally.

First of all, it’s a collaborative enterprise. It’s full of lots of individuals. I mean the Large Hadron Collider has 10,000 physicists from over 100 countries, speaking dozens of languages. And like I say, it’s a Gothic cathedral of the 21st century. But it’s also most often, what is healthy anyway, being driven by experiment. The experiment forces us to change our ideas. If you locked theoretical physicists in a room and had them come up with a picture of the universe, the picture they’d come up with wouldn’t look at all like the universe in which we live in.

IRA: Mm-hmm. Our number, if you’d like to join us, Dr. Lawrence Krauss, 844-724-8255, author of The Greatest Story Ever Told So Far. Is there any new physics that needs to be discovered for us to move forward? Of course you’re laughing at that. Even before I finished asking.

LAWRENCE: Well, I think you know the answer, of course. That’s the great thing about science, is each time we make a discovery, there are almost more questions than answers. So we sure– we discovered the Higgs particle. And it told us, it validated a notion which is so amazing, I have to repeat it. It validated that notion that there is an invisible field everywhere in the universe that allows us to exist. Which by the way, sounds religious, doesn’t it? But the difference is that invisible field that we postulated had to be discovered, and that’s what the Large Hadron Collider is about.

But the question now is, so we’ve discovered that that field exists, and we wouldn’t be here if it weren’t for that. The universe certainly isn’t designed for our existence. The fundamental laws in fact, wouldn’t even allow for our existence unless this field had frozen in the earliest history of the universe, and changed the properties of the forces we measure, and the particles that make us up.

But the next question is, why did it freeze? Why is it there? Why did freeze at– have the value it does? Does it indicate something? In fact, the scale that it froze at is a very unusual scale. Because if we think of the three of the four forces nature unify, it would happen in a very different scale. Why are the skills different? There are tons of questions that arise, now that we know what happened. The question I was going to say why it happened, but really the question is how did it happen?

IRA: And you know, since we talked about that discovery, there have been other discoveries. And since the Higgs, and I’m talking now about gravity waves. I mean that really–

LAWRENCE: Of course, gravity– I mean, the discovery of gravity waves is another amazing thing, which by the way, I would never have thought was possible. I mean, that’s the reason I’m a theorist, I suppose. I look at those experiments to measure gravity waves. LIGO had to measure a difference in length between two 4 kilometer long arms as the gravity wave comes by, it would cause the length of the two arms to change a little bit. But the amount to change by is 1/1,000 the size of a proton. I mean, who would have thought you could do that? It’s amazing.

But what’s really neat, is that this just opens up. We’re sort of like Galileo when he turned his telescope up to see the moons of Jupiter. We’re entering a new era of astronomy, gravitational wave astronomy, that’s going to reveal a whole new window on the universe. And every time we open up new windows, we’re surprised. And as far as I’m concerned, probably the most interesting surprise will be when we can measure gravity waves not from colliding black holes as LIGO did, but in fact, gravitational waves that are created at the beginning of time.

Because gravitational waves created in the initial moments of the Big Bang can actually make it here to us through that dense early universe, and we could actually probe a signal from a time when the universe was a billionth of a billionth of a billionth of a billionth of a second old. To test the idea that we’re building upon after the discovery of the Higgs. It will allow us to test not just how the universe began, but actually probe particle physics at a scale that’s probably 12 orders of magnitude higher in energy than we could ever do with accelerators on the ground. You’d have to have an accelerator whose circumference was the earth moon distance in order to probe the same kind of physics that we may probe with gravity waves from the early universe, it’s remarkable.

IRA: It is remarkable. And you know, it’s also a remarkable as you say, you’re a theorist. You don’t build them the equipment, you just go to the blackboard and talk about it.

LAWRENCE: Yeah, I just talk.

IRA: And you leave it up to the engineers, and whatever the guys who make– women who make these devices. To think that you could build– I mean, hearing you talk about the machine, the LIGO itself, how accurate it has to be. That’s almost an amazing event in itself, being able to parade–

LAWRENCE: It’s worth celebrating as part of The Greatest Story Ever Told So Far, it really is a great story. And LIGO is wonderful, but we shouldn’t discount the Large Hadron Collider, which is probably even a more complex system, in a sense that every second, more information is generated in it than in all the world’s libraries. It involves a vacuum tunnel that’s 26 kilometers long, where the vacuum is sparser than the vacuum of empty space. It’s amazing to think that humanity has built these incredible devices just to test these ideas about how we got here and where we come from. Directly, they won’t make a better toaster.

Some people say why is it worth doing that? What will it help us do? And of course, there are side benefits. [? CERN ?] produced ultimately the world wide web, for example, which we all rely on. But it’s not worth funding for those side benefits. It’s really answering those fundamental questions that you, and I, and everyone else has that makes us all scientists, in some sense. Why do we get here? How did we get here? Are we alone? All those interesting questions.

IRA: Are you fearful that some of the funding for basic science may go away? In this new–

LAWRENCE: Oh, absolutely. In the current climate, with the President’s budget that’s just come out, for example, cut fundamental funding for the kind of research I’m talking about by 20%. But it’s not just that, I’m as concerned about the cuts in science as I am about the cuts in the national endowment for the arts and humanities. And of course, relevant for this program, the Corporation for Public Broadcasting. These hit the fundamental aspects of our civilization.

The things that really make us great. There’s a wonderful quote that Robert Wilson, who was the first director of the Fermi national accelerator laboratory, a particle accelerator, when he was talking before Congress, he was asked would it aid in the defense of the nation. And he said no, but it’ll help keep the nation worth defending. And I think that’s really worth remembering today in the current climate.

IRA: Let’s go to the phones, lots of interesting calls. Let’s go to Mike in Houston, hi, Mike.

MIKE: Hey, how’s it going, guys?

IRA: Hi there.

LAWRENCE: Hi.

MIKE: Hey, I just want to make a quick comment about the Higgs boson particle. On the news last year, it was somewhat amusing. They said that in an episode of The Simpsons, Homer Simpson had roughly estimated the size of the Higgs-Boson particle like 10 years ago. Were you aware of that? Did you hear that?

LAWRENCE: No, I didn’t see his paper on the subject, actually.

MIKE: Anyway, I just thought I’d mention that. But secondly, with space travel, we use rocket fuel from the 1950’s. What do you think is the next generation of propulsion systems? And do you think–

[INTERPOSING VOICES]

LAWRENCE: We’re already using them. I think, to jump in. I mean, and Ira may have talked about on this program or others, that we’re using for example, electronic propulsion techniques where we’re basically using electric fields to propel atoms out the back of a spacecraft very fast. What it does, especially for deep space missions, is allows those rockets to move faster than they would with just chemical propulsion. So that’s certainly one of the new propulsion technologies. And as we look to go deeper and deeper in space, certainly conventional rocket fuel become less and less worthwhile. To get us out of the earth, maybe.

IRA: Do you foresee us in the near future being able to successfully unitize gravity with quantum.

LAWRENCE: With the other, right now, we know three of the four forces in nature. We’ve discovered them. And by the way, I will jump in and say often we think of the most exciting decades of the 20th century to be 1905 to 1925, when special general relativity and quantum mechanics were developed. But part of the reason for this book, is there is an unheralded 20 years, 1955 to 1975.

At the beginning of that, we understood one force of nature as a quantum theory, electromagnetism. By 1975, we understood three of the four forces of nature exactly as quantum theories. It was just an amazing development and a revolutionary one, that I think future historians may think is perhaps one of the most revolutionary periods in the 20th century.

But again, right now as you alluded, there’s one force that’s still an outlier, and that’s gravity. We don’t have a quantum theory of gravity. There are ideas of course, and string theory was developed to hopefully produce such a quantum theory. We don’t know if it is, in a sense. We don’t know if– it’s an interesting idea. But we don’t know if it relates to the real world yet. And the answer of course, Ira, is we don’t know. That’s what makes discovery so wonderful. People always ask me, you know, what’s the next big development? Now we say, if I knew, I’d be doing it.

IRA: May I remind everybody that this is Science Friday from PRI, Public Radio International. Talking with Lawrence Krauss, director of the Origins Project at Arizona State University, and author of The Greatest Story Ever Told So Far. Another great book, Lawrence, in the series of books that you have continued to do.

LAWRENCE: I’m very pleased with this book. You know, every book I learn something new, and I’m often surprised. In this case, the story, which I began to delve in, I knew the physics. But the actual history of it turned out to be far more for interesting than I imagined. When you see these people and these great scientists that I discuss, almost getting the right solution 10 or 20 years before it came out, and you just want to shake them and say, just look over here. You’ve got it all right there, it’s kind of amazing. In retrospect of course, things are always clear in hindsight.

IRA: That’s Monday morning quarterbacking, right?

LAWRENCE: Yeah, exactly.

IRA: Let’s go to the phones, see if we can get a couple of calls in here. Let’s go to Damascus, Maryland. Hi, welcome to Science Friday. Patrick.

PATRICK: Hi, thank you for taking my call. So Lawrence, I have a question for you. I had a few, but I think I’ll stick with one. I was wondering if it was in your mind, you felt that it may be a bit of a misnomer to call the laws of physics or nature laws, as opposed to properties.

LAWRENCE: Well, you know, why?

PATRICK: Well, I would say whereas laws feel like they constrain matter and energy, and then properties seems like it emanates from matter and energy.

LAWRENCE: Well–

IRA: Explain what the law of physics is. What does that mean, by law–

LAWRENCE: Well, it’s good. It’s a really good question in general. And a law is basically, it does constrain things. That’s why it’s well named. In physics, we really can’t say what’s possible, we can really say effectively what’s impossible. Because we do experiments that rule out ideas. And even the ideas that survive, may not be all the ideas. So a law of physics is something that basically is a theory that’s been tested by experiment. And a law that we find that every experiment tells us is not violated, and moreover, we have very sound theoretical reasons for understanding.

Let me give you an example. And it’s really important, because it points to some of the ways we don’t teach science correctly in schools. Often, we tell kids well, there’s a law of conservation of energy, and a law of conservation of momentum. And it sounds like that comes from the Ten Commandments, or something. That we just wrote it down and said this is the way it is. But we now understand that these laws derive from fundamental symmetries of nature. The reason energy is conserved, is that’s equivalent to saying the laws of physics don’t change with time, which we measure every day. And it’s really important if laws of physics did change with time, you’d have to take a different introductory physics class every year. And people really hate that.

The law of conservation of momentum comes from the fact that the laws of physics don’t change from point to point. These are fundamental aspects of the universe that are highly unlikely to change. And that’s why we have such great confidence that those laws ultimately do constrain any new theory. And any new theory will have to accommodate those facts. And if it doesn’t, it will have to explain in some sense how the laws of physics change from place to place, or from time to time.

IRA: Lawrence, wish we had more time. Always, always a pleasure to talk to you.

LAWRENCE: It’s always a pleasure to talk to you, Ira. Wish we had more time, too. I’ll come back sometime.

IRA: We’ll have you back. Lawrence Krauss, foundation professor and director of the Origins Project, Arizona State University in Tempe. Author of The Greatest Story Ever Told So Far, out next month on Atria books. Thanks again, have a good weekend Lawrence.

One last thing before we go, a special shout out to our listeners in Florida. Just 11 days, Science Friday will be onstage at the Bob Carr theater in Orlando. We’ll be talking about bionic arms, Navy missile decoys, NASA robots that can mine the moon. And yes, there will be robot demos on stage. I don’t know, maybe we’ll have a battle of the bots. Not promising, but the robots will be there. Who knows what could happen? Tickets are selling fast, so grab yours at sciencefriday.com/orlando. That’s sciencefriday.com/orlando 11 days from now on the stage at the Bob Carr theater in Orlando.

BJ Lederman composed our theme music, our thanks to our production partners at the studios of the City University of New York. Have a great St. Patrick’s Day, happy weekend. We’ll see you next week, I’m Ira Flatow in New York.

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