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Science Talk

Where's My Fusion Reactor?

Scientific American staff editor Michael Moyer talks about his article "Fusion's False Dawn" in the March issue, and Editor in Chief Mariette DiChristina discusses the rest of the issue. Web sites related to this episode include www.sciamdigital.com; www.snipurl.com/mikefusion

Scientific American staff editor Michael Moyer talks about his article "Fusion's False Dawn" in the March issue, and Editor in Chief Mariette DiChristina discusses the rest of the issue. Web sites related to this episode include www.sciamdigital.com; www.snipurl.com/mikefusion

Podcast Transcription

Steve:          Welcome to Science Talk, the more or less weekly podcast of Scientific American posted on March 17th, 2010. I am Steve Mirsky. Remember fusion? Not cold fusion; real regular old fusion that's going to solve all our energy needs. Well Scientific American staff editor Michael Moyer has an article in the March issue of the magazine about the current state of fusion called, "Fusion's False Dawn". We'll talk to him and we'll talk to Editor in Chief Mariette DiChristina about some of the rest of what's in the March issue—but first up, Michael Moyer.

Steve:          Michael, let me just read the subhead of the article, "Fusion's False Dawn". "Scientists have long dreamed of harnessing nuclear fusion, the power plant of the star, for a safe, clean and virtually unlimited energy supply. Even as a historical milestone nears, skeptics question whether a working reactor will ever be possible". So let's first of all talk about fission versus fusion very quickly, because some people might not be aware of the difference; because fission reactors exist all over the place. And also we'll talk about what that historic milestone is and then we'll talk about why it's possible we may never get fusion.

Moyer:          Yeah, fission reactors, as you say, are all over the place and those work by the splitting of heavy atoms such as uranium and more rarely plutonium to produce energy. Fusion is, you know, the opposite of that. It's a[n] atomic nuclear reaction, but it's the combination of two very light elements, generally hydrogen that come together and produce helium and then they also produce a lot of energy, and the energy comes from the basic fact that helium is slightly lighter than two hydrogens put together, so that excess energy has to go somewhere via Einstein's E = mc2

Steve:          The excess mass, it's converted into energy.

Moyer:          Yes excuse me, the excess mass gets converted into energy and quite a bit of energy, as anyone who's ever seen one of those film reels of hydrogen bombs going [off can] [at]test; that is just a little bit of hydrogen converted into helium, and wow!

Steve:          So, that's what we're talking about and hydrogen is available in bounteous supply, so it'd be a wonderful thing.

Moyer:          Hydrogen, [the] most common element in the universe and obviously we have it all over the place, not just in the atmosphere, but in the water. In order to make a workable fusion, we, actually scientists, use isotopes of hydrogen. Hydrogen itself just has a proton at its nucleus; if you have a proton and a neutron that's called deuterium. If you have a proton and two neutrons, that's tritium and for various technical reasons, it's much easier to make deuterium and tritium come together to produce fusion.

Steve:          Okay. So that's fusion. What's the historic milestone that's coming up?

Moyer:          So, for many years, ever since World War II, when people realized the power inherent here, they've dreamed of making a controlled fusion experiment. Control basically means it doesn't explode, it just moves along slowly and produces heat and you can then use that heat, and they've been working on this for decades and decades now and getting closer and closer to the point where they're producing actually more energy than they put into the experiment. It's very hard to push these two deuterium and tritium nuclei together because they have this repulsive force; they're both positively charged and so getting them close enough to fuse is very, very difficult and there's been a lot of different strategies for how to do that and it takes a lot of energy to make them come together. For the first time, maybe later this year, more likely next year, the National Ignition Facility, which is in Livermore, California, is expected to finally create more energy from their fusion reactions than they put in, which is called breakeven or ignition, and it's really a historic milestone. People had been working on this for half a century now.

Steve:          Despite all that, we're nowhere near a fusion reactor that would supply electricity for big populations, and it looks like some people think we may never actually get there.

Moyer:          Well, here's the thing: In theory, you think to yourself, "Okay, now we're getting more energy out than we're putting in; loop some of that energy back around." You have this multiplicative effect, and then suddenly you're able to get a reactor, which you're just putting in basically seawater and kind of getting out on the other side as much energy as you want to. You know, this is the world's energy problem solved. This is limitless energy—all we have to do is kind of get past this breakeven point and learn how to control it. That is not true for a lot of reasons. One of which is that the breakeven that the National Ignition Facility is going to be achieving is really just the energy that is going directly into the reaction. So the way the National Ignition Facility works, it's this amazing structure. When I was able to visit it; it's the most powerful laser in the world, three football fields in size and they generate this laser and then they focus all the lasers down, they split it apart into 142 different little lasers or, you know, not little but smaller; and then they focus it onto [a] little pellet of deuterium and tritium, and then that pellet, the outsides of the pellet kind of explode, and that pushes the insides ever closer together and that is what creates a fusion reactions. It's really just this marvelous, marvelous experiment, but into the accounting that they do—and they're very clear about this—it's just the energy of the lasers that are actually going in and hitting the pellets. There's a lot of losses in the system that come from generating the lasers themselves, so we're not there yet. More importantly, now you have all this energy coming out of the fusion, energy coming out, and how do you then convert that into energy that we could use? How do you make that boil water and spin a turbine and have that generate electricity that then goes out through the grid?

Steve:          What is the form of the energy that comes out right now?

Moyer:          So, the energy in a fusion reaction is mostly in the form of neutrons. And neutrons, one of the atomic constituents of matter, they're called neutrons, because they're neutral—they don't interact via the electromagnetic force, they don't have charge. So, you have all these neutrons coming out, they're very energetic, they've got all this energy, and they're blasting out through the sides of your chamber. Now you've got to somehow convert that into boiling water. How do you do it? Well you['ve] got to have this design around it, what's the called blanket; and what the hope is, is that the neutron will go out and the blanket is made of some very thick steel-type material, and every so often, a neutron will just hit an atomic nucleus in the steel blanket and that hit will then make the steel hotter and that hot steel, and then you have, almost like in a car engine, you have some fluid, water could work, going through the steel, it takes the energy away, that water is hot, it goes and spins the turbine, okay that's great. Problems: sometimes the neutron goes out and hits a nucleus of the blanket and instead of just ringing it like a bell, it goes and one of the steel atoms absorb[s] the neutron; now this makes it different material, [it] makes it brittle, it makes it radioactive. And in the blanket, they're figuring out [some of] the common materials wouldn't have a very long life. Another, actually huge problem that they have and probably the core problem that people are most worried about, as we said before, there's two elements that you have to have going into a fusion reaction, deuterium and tritium. Deuterium is very common, it's an element of sea water, you can find it; tritium is not common. Tritium is very difficult to make, it's radioactive itself, and right now you can make it in ordinary fission reactors, but only a very little bit and all at very high cost. Once you get one of the power plants going and up and running, you're going through kilograms and kilograms and kilograms of this tritium and you have to find a way to actually make tritium in this blanket at the same time that you're extracting energy. And so in order to do that, you have to have all these other components nearby and you have to have lithium, you have to have some of the neutrons hit lithium ions, and then it has to go through a cascade of reactions, so that the lithium goes and produces tritium and helium and then you have to extract the tritium from the blanket and you go ahead. It's just this huge, huge engineering feat that people aren't really sure of how they're going to solve right now; they haven't demonstrated that they're going to be able to do it. And so even as we get to this point, before we get to breakeven, now people are saying "Okay look, we've been working on this problem of making fusion reactions happen, controlling plasmas—plasmas are these very odd materials, when you heat things up to very high temperatures, and it's hard to control them. We're kind of getting this, in addition to NIF, there's this other program called, ITER, which is out in Europe, which will also be able to create controlled fusion reactions at above break-even that's going to be going online in maybe 15 years or so; they're building it right now. Now that we've done this, how are we going to make a workable power plant? And those problems are much more severe than anyone's been talking about.

Steve:          The last section of your article is sub-headed, The Big Lie, but it's not about propaganda, what is it about?

Moyer:          So, the big lie—once you take all these ideas into account, then you have to consider, are we going to be able to make these reactors and are we going to be able to make them work at [a] cost that is effective that is able to compete with whatever other options we have in 30, 40, 50 years and longer. And so people are starting to ask hard questions, for instance with the NIF program, as we said before, there're these little pellets in the center that all these laser[s] have to hit. So, but this it's really an issue where it's a blast. You have the lasers come and hit the pellet and the pellet explodes in a way, you know fuses together. Now, okay so that was one, now you want to kind of do this continuously. So you've got to kind of cycle things through and you almost, it's a machine gun approach. You got all these pellets coming in and blast, blast, blast, blast, blast. Right now, NIF is only set up to kind of run one blast every four or five hours or something like that, but you start to do, Ed Moses, the director of NIF told me, "You know, you have a 600 rpm machine, you start to create a lot of energy." Well, so then you ask the question, how much does the fuel cost? How much are these pellets? And NIF doesn't release the cost of their pellets and they're making them on-site there, but [there are] other people making similar pellets that have to [be] exquisitely machined, you know, down to micrometers, and right now the estimates are, they’re you know, in the order of about a million dollars a pellet.

Steve:          As opposed to a nickel a pellet.

Moyer:          As opposed to a nickel, which is where they have to go, and they and, you know, Dr. Moses will say, "Hey we have to get this cost down." He's very optimistic that they're going to be able to get it all the way down, but look that's a lot of orders of magnitude; you gotta get that pellet cost down.

Steve:          Well, we have seen the price of certain entities fall by that many orders of magnitude within a relatively short time. I'm thinking about consumer electronics.

Moyer:          Sure, and my hope is that they're able to make it happen, but the tolerances required are very small, and you also don't solve the tritium problem, with this as well, you still have to get the tritium from somewhere. Dr. Moses was telling me, we've seen progress like this in consumer electronics. He says the laser in the NIF right now is very expensive, but you can imagine that if we would have a solid-state laser made—they're making great progress in making solid-state laser[s] a lot cheaper—those you would be able to blast much more frequently. The limiting factor is in how often you can do the blast [at NIF now is that] you can only, kind of, run the flashlike-tubes that make the lasers so powerful every four hours, they have to cool down, they have to be able to do all this other stuff. So, can it happen? It could. Is it going to be this great stuff where in 20 years, we're going to start building these things? From [what] I learned in reporting the story, I'm not convinced.

Steve:          Alright. Let's just play a game.  Twenty years from now, what would you think the odds are of having a working fusion reactor that's actually supplying electricity to households in 50 years?

Moyer:          In 50 years, I guess I would have to fudge it and say it depends. A lot of the people, I spoke with said, "Look, if you gave us more money, we'd be able to make progress a lot faster." Moses is a big fan of a design which is more of a hybrid fission-fusion design. You have those, you kind of solve a lot of the blanket problems where you have your fusion blast in the center and then it hits a blanket which is basically nuclear waste, depleted waste, and there's a lot of left over energy in that waste; and you have neutrons hit that waste and then that catalyzes further reactions, you get a lot more heat. He says that that really can happen in 20 years if we want [it] to happen and other people in fission communities say that that's not really feasible. The standard answer I would say is, I would say that there's may be a 20 percent chance that in 50 years we'll have a working fusion reactor.

Steve:          All right. So what about 100 years?

Moyer:          There is a great optimism amongst everyone in the field that one day civilization will get to the point where we'll be using fusion energy.

Steve:          So, a thousand years from now?

Moyer:          That's right. At a thousand year[s], as T goes [to] infinity, the chances that we're using fusion for energy chances are….

Steve:          Go to 100 percent.

Moyer:          But in between now and then, it's hard to see where that slope of that line is right now.

Steve:          How come I haven't heard a lot about fusion in the last maybe 20 years really?

Moyer:          Well, I think it's a lot story of frustration. You know the early pioneers of the research made big promises; and you know, this was in the '50s and the '60s, this was the nuclear age, this was you know, "We can do anything if we put enough energy into it" and there were just a lot of you know, nature put up a lot of roadblocks along the way. And so then after hearing lot of promises for so long and not seeing results, you know, Congress stopped funding a lot of these things to the extent that they were before; and you know, the earlier energy crisis going back [to] the '70s, there was a lot of money put into fusion, but then that went away and so did the money. So, and then you also have the cold fusion fiascos of the late 1980s which kind of give everything a little bit of a bad name, but really it's because there hasn't been a lot to report since then. We've been working towards break even, now finally we’re getting to break even and that's great and the experiments that are going on, you know, aren't just for the purpose of getting us energy in the future, there's a lot of interest in science work that can be done. You can model supernova explosions with these little explosions at NIF. The real reason that NIF exists and the reason why it hasn't been canceled [for] going over budget is because it's used to help the stock[pile] stewardship program which is to help ensure the safety of Americas nuclear weapons stockpile, now that we can't test them anymore, there's a comprehensive test band. So there are a lot of reasons to do it that don't include making energy.

Steve:          Well, I hope that in the you know, we have the column "50, 100 and 150" years ago at Scientific American, so I'm hoping that the March 2110 issue quotes from your article here and talks about how ironic it was where you say that ignition may be close but the age of unlimited energy is not, and I hope those people [a] hundred years from now, in their hovercraft, as they're texting in they're hovercraft—its okay because it's on autopilot—I hope they're reading what we had a hundred years ago and think , "Oh those poor people back then, thank god [that] such a great progress has been made."

Moyer:          I certainly hope that they get a good chuckle out of it.

Steve:          Michael Moyer's article, "Fusion's False Dawn" is available in the March issue of Scientific American. The preview of the article can be found on our Web site and at http:snipurl.com/mikefusion. Mariette DiChristina is the editor in chief of Scientific American magazine. We talked about the rest of the contents of the March issue. March is here Mariette, and I understand there's now dark energy in the brain of all places?

DiChristina: Can you believe that?

Steve:          I can't actually.

DiChristina: You know the good thing about March is that the sun is actually now out more so the dark energy in the brain will maybe [be] ameliorated by the light outside.

Steve:          Interesting. And by the way, everybody who's now getting ready to write to us to explain how the Earth revolves around the Sun and spins on its axis and that the sun is not actually out more, we know.

DiChristina: We know, yes thank you. We probably addressed this in [the] Ask the Experts area of the Web site, too.

Steve:          No doubt. So let's talk about the brain's dark energy, obviously a term that the neuroscientists are borrowing from the physicists.

DiChristina: Right, in astrophysics and cosmology, what dark energy is referring to is this mysterious force that is responsible for the expansion of the universe at speeds greater than what have been anticipated, or I should say rates rather than speeds. In the brain, dark energy is this unexpected activity that they found by looking at, well let me back up just for a minute. It's when you're resting, say you're semi-dozing, you're kind of lying in your chair, you're kind of relaxed or even sleeping, once upon a time we had this idea, or scientists had this idea that the brain is pretty much inactive then, that you've shut off in effect your conscious thinking, then also your brain was not doing much. It actually turns out to be quite the opposite. In fact, when you're not doing much, the brain is super active, and this is the brain's dark energy. And the question was what is the brain doing when you're relaxing, you know, semi-slumbering; what could you possibly be up to?

Steve:          [One of] the really interesting findings is, let's say you are just sitting in a chair not doing anything, daydreaming or maybe just, sort of, maybe not trying to meditate but you are in a meditative kind of state, you're just sitting there relaxing, looking out the window, and you then decide to perform a task—your brain activity actually goes down.

DiChristina: Right it does. Well it goes down in the sense [that] it gets a little more focused as well; now know what's happening is this brain dark energy, which scientists call the brain default mode network—and they use the word default because when you're not doing anything else—this is background brain activity that is constantly occurring is all about the brain anticipating and predicting what'll happen next in the environment. This research by a guy named Marcus Raichle at Washington University School of Medicine in Saint Louis, the reason why he start[ed] to look at it was he began to wonder [whether]—all this brain wave activity when we look at, when scientists look at brainwave activity, they typically strip out what you and I would call noise. So you're trying to get that sine wave, that up and down mountain range of brainwave activity, and there's all these little wriggles in there that scientists once thought was noise. And what Dr. Raichle [asked] was, "Could that noise be actually doing something?" And it turns out it is. It is by far the brain's greatest level of activity, devoted constantly, and what is doing is thinking about the world; it's thinking about interpreting the data that come in and it's thinking about planning actions that one might next take for a background level of consciousness. 'The brain at rest' is actually a hive of activity and what it's doing is trying to sort out information that comes in; I mean this is another, another thing that made Marcus Raichle curious about this, is we know, for instance, that six million bits of data go flowing in through your optic nerve from the environment around you, and then only 10,000 of those bits actually get to the brain's visual processing area and only a few hundred of those are involved in consciousness, and you know, the conscious processing associated with that visual activity. So how on earth is the brain taking that little, relatively very small amount of data and then creating this very enriched, you know, very complete visual and, you know, sensory experience of the world around us and scientists think this default mode network is a key to that experience.

Steve:          A constant kind of reconstruction of reality.

DiChristina: Exactly, and a ruminating, you know, sort of considering what data it has taken in so far and what it might anticipate happening next, and you know assembling conscious processing to match that.

Steve:          So that's our cover article. You also have a really interesting piece by Robert Hazen, about the fact that the mineral diversity on earth is unique, well unique, as far as we know; because as it turns out so much of that diversity is the result of life itself on earth [itself] creating the minerals that we find on the planet. We always think of the planet as this inorganic, you know, nonliving environment, that life then takes place on but what this article shows is that life actually constantly remolds the physical non-organic environment. It's really interesting just how many thousands of the different minerals will not be found on the moon or Mars because life was[n't] involved in their creation.

DiChristina: Yeah, I love this article. This article is actually called the "Evolution of Minerals" and one of the things, as your rightly point out, that the article does is the author Robert Hazen suggests that, you know, we had thought of minerals for their timeless quality but actually they've been quite varied and diversified over time, just as life itself has, and that life has been the actor in this. You mentioned before how, you know, earth is unique as far as we know, and that is true. When earth was first formed with, you know, giant pieces of rock smashing, you know, impacting together, they were maybe 200 or so minerals created through the formation of the solar system and so on. And this is maybe, you know, 4.4 [billion] or 4.5 billion years ago, a little bit more, 4.6 billion years ago, through heat and pressure over the next few hundred thousand years, about another thousand or so minerals arose through chemical reactions, heating, weathering and so on. But then earth went through a series of three more giant stages associated with the formation of life that wholly revamped minerals. And so now there are something like 4,400 on Earth which is at least as far as we can see completely unique, and there was a period which Dr. Hazen called red earth about a couple of billion, two billion years ago, when life first gets going when there's some, you know, early forms of life and about 2,000 or so minerals arise [there], microorganisms make sheaths of minerals like calcium carbonate that we now see in animals with shells. There was an era called white earth which starts about 700 million years ago with alternating periods of deep ice sheets and then hotter warmer stages which led to formation of various kinds of crystals, and last and luckily we live in the period known as green earth, which started about 400 million years ago when multicellular life arose and wholly changed to biochemical breakdown the makeup of the minerals on the planet again. So [it's] a terrific article on how minerals have changed and how life and minerals back and forth had shifted each other.

Steve:          And one of the key things is that life is responsible for the oxygenation of the atmosphere. There was a very, very miniscule percentage of the atmosphere that was oxygen until living things started to produce oxygen and oxygenate the whole big deal here; and the oxygen in the atmosphere basically rusts the earth.

DiChristina: Everything yeah, this is red earth, you're referring [to] Steve; it's an event called the great oxidation event and this started about two billion years ago and really set off the first giant wave of mineralization of changing varieties of minerals that we see in earth's history.

Steve:          Well, once you have oxygen out there to combine because it's so corrosive …

DiChristina: So reactive yeah.

Steve:          … to combine with all these other elements you have this just incredible variation of minerals that become available too.

DiChristina: Yeah, I mean, we think of minerals as things that just kind of sit there, and they are timeless, and they don't change, but what this article shows is that they've changed in extraordinary ways over time. That's fascinating.

Steve:          Yeah, it's also a good reminder that we always perceive things through the human lifespan, and when you can hold back from that and see things over geological time spans, everything, sort of, takes on the appearance of being alive, even the rocks.

DiChristina: Right, well even they change, I mean if we then change our lens again, you know, the solar system is evolving and changing the galaxies and so on, and in fact the entire cosmos seems to be alive with change.

Steve:          And one of the interesting things Hazen points out is that if we are searching for life on other planets with our telescopes—we don't have to actually go there yet—one of the things we can do in addition to looking for the direct signatures of life, biochemical signatures of life, we can look to see what kind of minerals appear to be on those planets. Because if there's just a handful, chances are it's a dead planet. But if we find another body out there with just an incredible variety of mineral forms that might be a clue to us that there is life there creating those mineral forms.

DiChristina: Right, I mean and that would be, as you say, we could look with our telescopes and we could see chemical signatures using special instruments with our telescopes and look for those signs of potential life.

Steve:          So, we have another article everybody loves: worms.

DiChristina: Who doesn't love a good worm?

Steve:          Seriously, so worm grunting; we [have an] article actually on worm grunting; let's explain what worm grunting is.

DiChristina: Yeah,  [we have] an article on this amazing, on this amazing phenomenon which is so counter-intuitive. I mean evolution teaches us, we [were] just speaking about evolution and minerals, right, and evolution of the brain. Evolution teaches us that survival is a good thing. So one would think that anything you do counter to survival will not be a good thing, and with worms if you stamp on the ground, worm grunters do this, the worms will rise to the surface. Why would they do that thing? Why? Because they come to the surface and now they're subject to you who are just stamping and want to pull them off for fish bait, or other animal forms, why would they do that?

Steve:          A perfunctory analysis would be if you hear stamping on the ground, you would go deeper down to get away from whoever is making that noise up there, which might be a threat; but no, they come up.

DiChristina: Even Charles Darwin wondered about this puzzle, and he had an idea about it; he thought that it may be the worms were trying to escape a predator, moles who are seeking protein in the form of wriggling worms. And the thing is that's a nice just old story, right? Maybe the worms just do that; Charles Darwin had this idea but how do we know that's what happened? And this is where this article, which is called "Worm Charmers" by Kenneth Catania comes into play, because he had the same question—could we prove that moles, that they were indeed trying to escape moles who were digging and that they might rise up to escape the moles that were in tunnels below them.

Steve:          So our buddy Ken Catania goes to Florida and he tracks along with some of these worm grunters or worm charmers.

DiChristina: Right so first he has got to find some moles, so he is driving down the highway and he looks for characteristic tunnels that moles form, and he finds them; and then, you know, how are you going to get the mole out of the tunnel? Well some of the tunnels were crushed by cars passing by so you would wait for moles to come out and kind of fix the tunnel and thereby find them.

Steve:          And once he found them what was he going to do with the moles directly?

DiChristina: Well you can set them to work then back on the ground and then see what the worms do, so in this way you can directly test what the animals are doing, you know, whether they interact with each other.

Steve:          And lo and behold when the moles burrow they actually set up these vibrations that are very similar to what humans do when we stamp on the ground.

DiChristina: And so the worms will rise up to escape them. And what else is interesting about that is that there are other animals that have figured out, as human worm charmers [have], that if they set up vibrations on top of the ground, worms will rise to meet them.

Steve:          So the moles are setting up these vibrations. The worms attempt to flee because they know that those vibrations mean burrowing moles and they come to the surface, so human beings have co-opted that vibrational form which they mimic by stamping to get the worms to come up, but so have these other species, have figured this out. So, was it herring gulls have also figured it out that if they stamp on the ground with their big web[bed] feet that they can get the worms to come up and get a meal out of it? And what’s the other animal?

DiChristina: There is a wood turtle that also stomps to drive up worms.

Steve:          Also, with the big webbed foot, smacks the ground, brings the worms [up]; and, of course, the turtle doesn't know that it's imitating the vibrational form produced by the moles, it's just figured this out evolutionarily.

DiChristina: Right, I mean it happens, it proves to be successful strategy for acquiring protein in the form of worms and those animals that develop this successful strategy or can pass it on in whatever means survive better and that way the behavior continues.

Steve:          So, the worms are caught in, I believe the expression is an evolutionary trap, where their survival strategy has now become deleterious to them.

DiChristina: Well, there is, yeah, but it is and it isn't. So in some cases, this behavior is, you know, a survival advantage when the moles; and, you know, clearly when Kenneth Catania was driving around he found lots of mole tunnels, so there are lots of reasons for worms to rise up and get away from these moles. But in other cases other predators, such as humans or this herring gull or that wood turtle, you can mimic that vibration and can take advantage of it.

Steve:          And we should say that the herring gulls finding was made by the renowned Nobel laureate Nicholas Tinbergen actually who did a whole lot of interesting stuff on animal behavior that’s worth checking out, so do a Tinbergen google.

DiChristina: I think I will do that right after we are done here.

Steve:          So let's take a quick look at our "50, 100 and 150 Years Ago" space here compiled by Daniel Schlenoff. One hundred and fifty years ago in Scientific American, the March 1860 issue, we wrote "… gas for interior illumination, it is supposed is a powerful disinfectant, and hence there is no contagion within the circle of its influence"—actually we were then quoting, and then we wrote: "We copy the above sentence for the purpose of disputing the inference that gas will protect people from the smallpox. Smallpox is doubtless uncommon among that class of people who burn gas for [light] in our cities because they generally have sufficient intelligence and forethought to attend to the vaccination of their families and its ravages are almost wholly confined to that improvident class who make no provision against the smallpox or anything else in the future and who live by the light of burning fluid." So a 150 years ago—there's undoubtedly some classism involved in our interpretation back then—but 150 years ago at least we were pointing out the difference between causation and correlation.

DiChristina: I was just going to say, that's one thing also what occurred to me is that to me is a lesson in microcosm—because it's just a paragraph what Steve just read to everybody—that shows why it's so important in science to remove all your confounds, you know, remove all the variables so that you can find really what is at the heart of thing, and to me that that's the lesson that science has much more thoroughly adopted probably at this point and can speak with, you know, much greater authority; when something actually is a finding you need to be able to remove all the potential things that could be interfering with the conclusion that you're trying to make.

Steve:          Absolutely, and 150 years ago we were pointing out that it was really a good thing to get vaccinated.

DiChristina: And it is today—; go get your shot folks.

Steve:          The March issue of Scientific American is on the newsstands and it's also available in its entirety at www.SciAmdigital.com. We are running very long so that's it for this episode. We'll roll out our TOTALL…… Y BOGUS quiz as a stand-alone feature pronto. In the meantime, get your science news at www.ScientificAmerican.com or you can see the slide show illustrating six fun facts about the James Webb Space Telescope. For Science Talk, I am Steve Mirsky. Thanks for clicking on us.

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