Science Talk

Physics Now and Then: From Neutrinos to Galileo

Theoretical physicist Lawrence Krauss, director of the Origins Initiative at Arizona State University, talks with podcast host Steve Mirsky about neutrinos and gravity waves. And Cynthia Graber talks with Paolo Galluzzi, director of the newly reopened Museo Galileo, the science museum in Florence, Italy. Plus, we test your knowledge of some recent science in the news. Web sites related to content of this podcast include

Theoretical physicist Lawrence Krauss, director of the Origins Initiative at Arizona State University, talks with podcast host Steve Mirsky [pictured] about neutrinos and gravity waves. And Cynthia Graber talks with Paolo Galluzzi, director of the newly reopened Museo Galileo, the science museum in Florence, Italy. Plus, we test your knowledge of some recent science in the news. Web sites related to content of this podcast include

Podcast Transcription

Steve:          Welcome to Science Talk, the weekly podcast of Scientific American posted on June 15th, 2010. I'm Steve Mirsky. This week on the podcast.

Krauss:          A neutrino like the neutrino that is coming through the body from the sun can go through an average 10,000 light-years of lead before interacting once.

Steve:          That's theoretical physicist Lawrence Krauss, director of the Origins Initiative at Arizona State University. We will talk to him about neutrinos, and we will hear about the reopening of the Institute and Museum of the History of Science in Florence, Italy—now known as the Museo Galileo. First up Lawrence Krauss, who is also a columnist for Scientific American. We were both at the World Science Festival in New York City last week. His column in the June issue deals with neutrinos, so we talked about that and some other physics-y things.

Steve:          Why do you love neutrinos so much?

Krauss:          Because they're the most interesting particles in nature, they're everything you would want. They are elusive and mysterious; you don't know much about, them and 6,000 billion of them are going through your body every second. I mean, you know, how much more exciting can that be?

Steve:          Can you give us real quick explanation of what neutrinos are, for people who don't know?

Krauss:          Absolutely. Neutrinos are elementary particles that are the lightest elementary particles we know of. They are, in fact, were invented or discovered because when particles like neutrons decay, there was missing energy; and these particles were proposed that the energy had to go somewhere. And, in fact, the name comes from the fact that they had to be neutral because we couldn't see them in detectors, but they had to be light. So, Enrico Fermi called them "little neutron" and in Italian that's "neutrino", so they were baby neutrons which were the only other neutral particles at that time they were known. But it turns out that they are unique in nature in only interacting via a single force in nature called the weak force, and the weak force is weak. So a neutrino, like the neutrinos coming through, your body from the sun can go through on average 10,000 light-years of lead before interacting once.

Steve:          Let's just try to bring that down to Earth to people. If you had a block of lead the size of the entire Earth and you went across the diameter that would only be about 8,000 miles and you're talking about 10,000 light-years which is, you know, somebody else can do the math, but it's …

Krauss:          It's the third of the way to the center of the Milky Way Galaxy.

Steve:          So that's a lot of Earths lined up in a row.

Krauss:          Yeah, [a] heck of a lot of Earths lined up in a row, that's a distance that encompasses something like almost a hundred billion stars. It's amazing. And neutrinos go right through it without even knowing it was there.

Steve:          So in the column…

Krauss:          And what's amazing by the way, and what is equally amazing and one of [the reasons] I love it so much, is you might think that given that they don't interact at all like this, how do we know they exist? Maybe they're just inventions of our human imagination. We use the laws of probability, which I also love; all those neutrinos are going through the Earth on average without knowing it was there, but the laws of probability tell us that every now and then one should interact. So, [if] we build a big enough detector and we are patient enough every now and then we can catch that errant neutrino [and] whether it's interacted. And in fact, that's what Ray Davis in a very courageous experiment did with a 100,000 gallons of cleaning fluid in a deep mine in South Dakota for years. It's amazing the experiment got built, and he later won the Nobel Prize for discovering [the] neutrino. And this is [the neat] thing in that experiment; so what he [did was he] built a tank of 100,000 gallons of cleaning fluid, and you can calculate that if these neutrinos were coming from the sun and on average there are billions and billions of neutrinos that went through the Earth, one each day would hit an atom of chlorine and turn it, the nucleus of that atom, into a nucleus of an atom of argon. So, all he had to do is find a single atom of argon in 100,000 thousand gallons of cleaning fluid. [And] when I tell that to an audience, people titter all the time because no one would believe it was possible—science fiction writers wouldn't have the guts to talk about it—but you can really do it and that's what's amazing, that nevertheless just amazes me, that we can detect neutrinos.

Steve:          And in the column, you wrote in the June issue of Scientific American, you talk about some of the ideas that you had a long time ago related to neutrino detection. Why don't you tell us about that and what eventually happened?

Krauss:          Yeah, now that's amazing because you think of things—and I'm a theoretical physicist; I [get paid] to imagine a lot—and there are times when I think of things that should be possible; but it's never clear we'll ever really know about it, and then so, in fact 25 or 30 years ago, I thought of two processes that would produce neutrinos, that were fascinating to me; one because I got to learn about it. One is the fact that the Earth is actually a source not of neutrinos but antineutrinos. The radioactivity in the Earth produces antineutrinos which are constantly streaming up, and I actually, kind of, realized that if we can measure those antineutrinos we could measure the radioactivity in the Earth. One of the things that is kind [of] fascinating is we don't know how much radioactivity there is in [the] Earth. In principle we don't even have proof that the Earth isn't heating up instead of cooling down, because if there was enough radioactivity, it could heat up the Earth instead of letting the Earth cool down. By measuring those antineutrinos we could know that; but it was so clear that it was such a difficult experiment that while I proposed a lot of possibilities, I remember at the time I lectured on this subject to geophysicists; and a lot of them said, "Look, when I was going to school, people didn't even believe neutrinos existed. Now, you want me to use them to look for the [radioactivity of the] Earth?" I remember people scoffed at it, you know; at least they were amused, but didn't take it seriously, I think. And then I also thought about the fact that over the history of the life of the universe, neutrinos are not just produced by the sun, but when stars explode in a supernova, the most brilliant fireworks in the universe, as brilliant as those fireworks are, less than 1 percent of the energy of the star is coming out in light; 99 percent is coming out as neutrinos and so neutrinos are being, [and] every time [a star explodes there's] an incredible burst of neutrinos. We hope to look for that. In fact we discovered a neutrino burst in 1987 from a star that exploded 150,000 light-years away. But, if you think about it, all of the stars that have exploded over cosmic history have produced a neutrino background that's going throughout the universe. And we estimate[d] what it might be—at a time, by the way, before 1987; before we'd ever seen a star explode and produce neutrinos, so no one really knew if it happened. So it was theoretical speculation in the extreme: We imagine stars produce neutrinos, we imagine the rate at which stars were exploding, and we proposed a rate to [detect] them. Well, I was going to say the short version, but this wasn't that short because I have talked [for awhile,] is that 30 years later, [there are now] experiments [that] have detected the antineutrinos from the Earth; finally [experiments that] I would never would have thought were possible. And an experiment is on the verge of having the sensitivity to detect that neutrino background from the universe. And each time we open up a new window on the universe, we learn something; we're often surprised. And so neutrinos are becoming not just elusive particles but an incredible new windows on processes that happen in the cores of stars and even in the core of our very Earth.

Steve:          When something like that happens, where you have this one idea, and you theorize that this happens then, if A happens and B will happen and if C happens then D will happen, and years later you get both B and D, well this is a real indication to you that your overall picture of the universe is pretty accurate.

Krauss:          Well, yeah, but it's scary, is what it really is. When you're sitting alone in the middle of the night imagining stuff about how the universe might behave, and then 20 years later you find out the universe really behaves that way, it's scary. It really is; it sometimes [is] very difficult to believe that that universe is really behaving like you thought it might. And it's much perhaps, much more relieving when you find out you're wrong, because it just seems too weird that somehow it all worked so well. And in this case with neutrinos it has worked so well. Often if you're a theoretical physicist, you want to be wrong, because you want the universe to be more exciting. In this case, it is really gratifying when theoretical ideas [that] are based on [sound] science from one area can be extrapolated and allow us to use those principles to learn and explore the universe in new ways. It really is amazing, and as I say, it's a little unnerving.

Steve:          Is the unnerving part of it, the feeling of why should my little brain be able to figure all this out?

Krauss:          It's exactly the case: Why should our brains be tuned to be able to understand the universe? If you're a theoretical physicist, it's very surprising often, and I am here in New York and I am doing some events, and I've written about many things, obviously including extra-dimensions most recently, and you have got to wonder sometimes when you're thinking about something and you find it attractive, is it because the universe is that way or is because your brain is hardwired to like that? And then you have to wonder, well if your brain is hardwired to like that, does it have any relation to [the] universe? And you've got to be very prepared. Too many people like to— and this is a big problem and scientists have to get over this problem and so do members of the general public—just because you like something doesn't mean it's true. And that's probably the most important thing we learned from science. For me, one of the greatest things that science can [tell you] is to have some idea that you love that you think is beautiful, profound and elegant shown to be wrong, because it opens your mind.

Steve:          Somebody said we have to hold our theories dearly but gently.

Krauss:          Exactly, or you know, to make another bit of self-promotion, I finished a book on Richard Feynman that's coming out, and he said it very well, he said, "Science is imagination in a straightjacket." And I think that's really important because the universe is the way it is like whether we like it or not, and that's one of the greatest things about science as far as I am concerned.

Steve:          The straight jacket being the constraints: You can have a lot of freedom but it's within those constraints.

Krauss:          Within the constraints of reality and experiment. And you know, [as] beautiful [as you] idea is, if the experiment goes wrong, it's thrown out like yesterday's newspaper.

Steve:          And the Feynman book is called…

Krauss:          Quantum Man: Richard Feynman's Life and Science.

Steve:          And that will be out in early 2011.

Krauss:          February or March 2011.

Steve:          What else are you thinking about?

Krauss:          I've been, lately I've just been thinking about gravitational waves from the earliest moments of the big bang, and I just produced a scientific paper about that. And those will be another new wonderful window because they haven't interacted since [the] universe was perhaps 10 -30 seconds old, so they may be the newest window that will eventually reveal to us a lot about the early moments and maybe why the big bang happened, and ultimately as I like to say, [help us] understand why we're here. So that, dark matter and a few other things are currently occupying me.

Steve:          How're we going to find gravity waves?

Krauss:          Well, the neat thing is that we're building detectors to look for gravity waves. When a gravity wave comes by it actually shrinks space momentarily and expands it. And so we actually have very careful measuring rods and we can measure the length of two different measuring rods in different places—[it's] called an interferometer—and we look for one of them to, one length to change relative together. It's amazing we can measure now with the LIGO interferometer and in [there's] one in Washington State and one down in Louisiana. They are two three-mile-long cavities where we measure the length of those cavities and we look for, we can measure those lengths with an accuracy smaller than the size of a proton; it's amazing what experiment can do. And so that' s a direct way. But it turns out we can actually indirectly measure gravity waves by looking out at the cosmic microwave background that's come to us from the big bang and imprinted in there, it turns out for reasons I think I won't talk about here, [is] a signal maybe of the big bang and I've just, in fact, written a bit about how you might be able to entangle that signal.

Steve:          Well, we'll have to look for that in longer treatment in the pages of Scientific American.

Krauss:          Absolutely. Good idea. I'll have to do that.


Steve:          One of Lawrence Krauss' scientific forefathers is, of course, the great Galileo. On June 11th, the science museum in Florence, Italy reopened with a new name that pays tribute to Galileo. Cynthia Graber, a frequent contributor to the daily SciAm podcast was recently in Florence and spoke to the museum's director prior to the reopening. I will let him introduce himself.

Galluzzi:          Paolo Galluzzi, director of the Institute and Museum of the History of Science, which is going to [become] the Museo Galileo very soon.

Graber:          And why this switch from the Institute of Science to Museo?

Galluzzi:          Well it's a new phase of the history of this institution, [it's a] huge rearrangement of the collection[and] restructuring of the building, and so we make a full [point] and we start a new phase of our history and in the name of Galileo, in the wake of Galileo.

Graber:          And so what are some of them that are going to be going on in the new museo, in the new exhibits?

Galluzzi:          Well, it will be totally renewed, there will be new rooms, new plans, new systems of communication; we are using and exploiting a lot of information technology in favor of understanding on the part of the visitors; new graphics, new concepts, so everything will be fairly new.

Graber:          I read something about Galileo's fingers. What is that?

Galluzzi:          Yeah, we already have one finger of Galileo [that] was taken from his body or remains of his body in 1737 when the corpse of Galileo was moved from the original burial to the monumental [sepulchre] in Santa Croce. And now we know that on the same occasion, another two fingers and one tooth were taken from the remains, but we had lost traces of these other documents, and luckily recently it has been up for auction, and not knowing what it was about, and we were lucky enough to discover what it was. And the person who [bought] them offered to us, and [they] will be displayed for the first time on the opening of the museum in May.

Graber:          Why would people have stolen parts of his body?

Galluzzi:          Well, do you know what's happening with the famous religious men? Relics. You [have] relics of religion and you have relics of science; these are relics of science, and Galileo was the saint of science. And also it's a double meaning, because he is a saint [who w]as being persecuted by other saints, so it's of quite [a lot of] value.

Graber:          How are things like that, how were they preserved?

Galluzzi:          They were preserved in a container, glass container, as a trophy, and they were possibly intended as homage to the memory of this great man [who] was fighting in favor of reason against superstition.

Graber:          What are some other things that visitors to the exhibit should be looking out for that you're very excited about?

Galluzzi:          Well, we are excited because the collection we have the privilege to preserve [is] certainly the most important collection, in as far as instruments of ancient mathematical science and physics are about around the world, so this is very exciting itself. The second fact, they are very beautiful objects. Third, we are offering visitors an interactive way of communicating with our objects through it, very small objects will be in their hands and will tune them directly with the objects on display. And they'll be able to put questions, and to ask about [how] their working, having animations of the [instruments] working, reconstruction of the context, historical information about the moment in which we discovered, the makers' biography and many other things. So it will be a totally different way of approaching visitors and will make a non-interactive museum, because it hosts original objects, into an interactive knowledge exchange. And we have organized in the ground floor and in the basement exhibitions at the moment, currently we have an exhibition on the late phase of the  Lorraine Great Duchy of Tuscany domain, and this is about physics and mathematics in the end of [the] 18th century and first half of [the] 19th century, and this is an interactive exhibition on historical objects.

Graber:          Is there something else I haven't asked that you would want [to tell] Americans [who are] interested in science and might come to Florence?

Galluzzi:          Well, I mean, when Americans come to Florence, I know that Americans love Galileo and consider Galileo as a great man in history, as is correct to do of course, and next time pay a visit to the Galileo museum. It is just aside nearby the Uffizi; you will not miss it.

Steve:          Galluzzi and Cynthia took a close look at one of the museums prized possessions, a 400-year-old armillary sphere, a pre-Copernican model of the universe.

Galluzzi:          That was completed at the end of the 16th century in the 90s, and under Ferdinand I,  the Grand Duke of Medici, Grand Duke of Tuscany, by a person whose name was Antonio Santucci. [He] was a colleague of Galileo at the University of Pisa but was Ptolemy follower and was not a Copernican. And this is a Ptolemy representation, [a] Ptolemaic representation of the universe. But what is impressive is the structure of this: You see the piece is three meters high, and that will be greatly spectacular. You were looking for something of interest that should be seen when the museum is reopened—this will be very fantastic; it is a combination, of course, of art and science.

Graber:          So the Ptolemaic as opposed to the Copernican means what?

Galluzzi:          Oh, it's geocentric, Ptolemy, and heliocentric, Copernicus. So this is the, as you see here, the Earth is in the central position and all the rings, [the] armillae, are going around in a circular [way], although you have some connection, and [there are] lots of paintings.

Graber:          And what is the painting up here?

Galluzzi:          [It's a constellation:] Leo; [there are] zodiacal signs, and all the signs are beautiful and top of that there is a ring; this is not a ring, it's a round circle with God, who is looking at the cosmos, embracing the cosmos.

Graber:          So there are the planets and the sun.

Galluzzi:          Sure, you've all the circles of the planets and you have, of course, including the sun that was earlier treated as a planet; and you have all the major astronomical circles, the ecliptic. And this is beautiful; it's a spectacular object. When you will see it installed here, you can see from here it will be breathtaking

Graber:          So , this will be going up towards the roof?

Galluzzi:          Yeah, that high.

Graber:          That's amazing.

Galluzzi:          Yeah, three-and-a-half meters high; it's beautiful, even though it's that old, degraded gold.

Graber:          And beautifully preserved.

Galluzzi:          No, it was restored.

Graber:          That's what I was wondering.

Galluzzi:          This is coming now after restoration, it has never been touched after 1590, when it was finished, and now we have [dismantled it], quite an endeavor, and then we reinstalled it, and it has been fully restored.

Graber:          How long does it take to restore something [like this]?

Galluzzi:          A couple of years.

Graber:          And I imagine that takes a lot of science in itself to know how to restore it?

Galluzzi:          Yeah, to reinstall according to the coordinates and respecting, but installing it will be easier than [dismantling] it, I guess.


Galluzzi:          Because it has been manipulated in the past, but manipulation means that the position did not correspond anymore to the project, so [we have] made a study to understand how should that be arranged, and then [it] has been [dismantled]. And now [there are] pieces [that] were leftovers; we had a box of leftovers.

Graber:          So there were things that weren't or that had not been added [correctly].

Galluzzi:          Yeah, they didn't know. [But] now it has been reconstructed correctly. So it's been a scientific project before going to restoration and now we have replaced the original design. [In] 1590, it was given to the Medici and was displayed in Uffizi and then was moved, we have found that here but we didn't know how it came, it was [dismantled] and not correctly [dismantled] because there were leftovers.

Graber:          So how did you figure out what was correct then, if it hadn't been correct [before]?

Galluzzi:          Well, we know from the fact that these kinds of instruments were pretty common in the period; second we have the precise design by the author of how it should be, so it was in [a] sense easy to bring back.

Graber:          [By precise]  design, you mean there are images that are …

Galluzzi:          Engravings; there is a detailed engraving by the author himself. It was [printed], because only a few people could see the original, so [he] wanted to make it more popular through the engraving.

Graber:          So you said that it told us something about what the world we, what we knew about the world in the 16th century, too?

Galluzzi:          Yeah, it's the older view of the universe, that is Ptolemy's geocentric universe, and it's a representation that is very spectacular of [the] visual appearance of this old cosmology and was an object, of course, for the Medici to display producing surprise and emotion in their guests.

Steve:          For more on the Museo Galileo and to see images of the armillary sphere go to

Now it's time to play TOTALL……. Y BOGUS. Here are four science stories, but only three are true, see if you know which story is TOTALL……. Y BOGUS.

Story 1: Being superstitious can affect your performance on a task.

Story 2: In England and Wales, professional drivers were found to be five times as likely as other people to get Legionnaires' disease.

Story 3: Chimpanzees who lose a tussle with another member of the tribe are shunned by their comrades for hours following the fight.

Story 4: Lindsay Lohan's bail was doubled when she was found to be in probation violation. She was turned in by her ankle monitor which revealed that she had consumed alcohol.

And time's up.

Story 1 is true. Being superstitious apparently can alter your performance. Researchers did a few different tests but one in particular illustrates the self fulfilling effect: Subjects who had lucky charms set higher goals for themselves [than] those who didn't have their charms available and worked harder and longer on the given problem. The research appeared in the journal Psychological Science.

Story 2 is true. English and Welsh drivers were found to be at five times the risk of Legionnaires' disease according to Great Britain's Health Protection Agency, and the culprit was windshield wiper water. Warm, still water is a great place for the Legionella bacteria to grow and wiping the window sends out a spray of water, some of which occasionally reach the lungs of drivers. Adding wiper cleaning fluid to the mix seems to wipe out the bug.

And story 4 is true. Lohan's ankle monitor can and did detect alcohol. It's called a SCRAM, for Secure Continuous Remote Alcohol Monitor, and it measures alcohol in the sweat that it samples. As for this particular case, somebody said that fame is such a powerful intoxicant that Lindsay Lohan gave up being a movie star for it.

All of which means that story 3, about the shunning of chimpanzees who lose fights is TOTALL……. Y BOGUS, because a study done by researchers at the Yerkes National Primate Research Center finds that the losers in aggressive interactions were often consoled by bystanders. However the chances that a loser would be consoled increased with the loser's overall ranking in the group's social standing. For more, check up the story on our Web site titled "Simian Solicitude: Like Humans, Chimpanzees Console Victims of Aggression".

Well that's it for this episode. Get your science news at, where you can check out the In-Depth Report, "Urban Visions: The Future of Cities" and our slide show, "The Top 10 Dogs of Science". Follow us on Twitter, where you'll get a tweet every time a new article hits the Web site. Our Twitter name is @SciAm, S-C-I-A-M. For Science Talk, the podcast of Scientific American, I'm Steve Mirsky. Thanks for clicking on us.

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