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Steve: Welcome to Science Talk, the weekly podcast of Scientific American for the seven days starting November 14th. I am Steve Mirsky. This week on the podcast: From Nukes to Neuroscience. Scientific American's David Biello talks about his article in the November issue that examines America's nuclear arsenal and options for the future and Scientific American Mind magazine'sKaren Schrock gives us a rundown from the big neuroscience meeting, that she attended last week. Plus, we'll test your knowledge about some recent science in the news. First up, David Biello: He is an associate editor of our Web efforts, www.SciAm.com, and he contributes articles to both Scientific American and SciAm Mind magazines. The November issue of Scientific American features a special section called "Nuclear Weapons in a New World"—Dave's article is titled "A Need for New Warheads?" We spoke in the SciAm library.

Steve: Hi Dave. How are you doing?

Biello: I'm very well. Thank you.

Steve: Glad to hear it. You've got this article in the November—that's the issue—Scientific American, "A Need for New Warheads,"and right on page two of the article, you actually list my first three questions, and they are: What is the purpose of the U.S. nuclear arsenal? What should it be composed of and how many weapons are necessary? So why don't we start with those? What is the purpose at this point in this geopolitical world, this geostrategic situation—what is the purpose of the U.S. nuclear arsenal?

Biello: Well, that's a great question because the…

Steve: Because you raised it!

Biello: (laughs)Oh! Yes, for that reason alone, but also because many of the great statesmen of our country have not come up with a great answer to that question. Obviously the original purpose of the U.S. nuclear arsenal was to deter the Soviets. The Soviet Union ceased to exist in the early 1990s and one would think that the purpose of the U.S. nuclear arsenal would have changed subsequently, but that hasn't been the case. We still have about 10,000 nuclear weapons, which is much less than we had at the time, but still many more than potentially we need, according to some critics, and we still have them largely pointed at the Soviet Union, Russia and other geopolitical threats, like China.

Steve: Let me ask you, there is a photo on the same page of a submarine carrying ballistic missiles with nuclear warheads?

Biello: Correct.

Steve: Now, when I first started as a journalist, and I haven't asked anybody this question in many years, but I would call a military base and ask them about their nuclear weapons and the stock answer was always, "We can neither confirm nor deny the presence of nuclear weapons at this facility." So how do you get this information? I mean, is that still true? Is that still the answer you get? I mean, some people you spoke to obviously went on record here.

Biello: Yes, there are some specific sites that are known to be bases for nuclear-equipped submarines and that gets into the issue of safety, some who hope to build new nuclear weapons want to make them safer by installing certain safeguards, so that if they fall into the wrong hands, they can't be triggered or used against us, but it is still largely unclear where the vast majority of these 10,000 weapons are. They kind of alternate between storage, being on submarines throughout the world, being in silos in South Dakota etc., etc.

Steve: How do we even know though that there are 10,000? Is that the stuff that comes out when there are treaties that get ratified?

Biello: In large part, but 10,000 is also just an estimate; it could be slightly more, slightly less; 10,000 is a nice round number that many experts that I interviewed kind of agreed upon.

Steve: So they are working from basically other information, just looking at what kind of facilities exist and they are making their estimates based on that and how many people work there...

Biello: And how many weapons were produced in the past, how many have been explicitly retired; all that kind of information.

Steve: So, okay. The answer to question one is—what is the purpose of the nuclear arsenal at this point?—is really unclear.

Biello: Up for debate.

Steve: That hasn't been agreed upon and, in fact, you talk later in the article, you talk about some really big names in foreign policy and in defense strategy, signing a letter to the Wall Street Journal, just recently, Sam Nunn, Henry Kissinger, George Shultz and Bill Clinton's defense secretary, William Perry.

Biello: Correct.

Steve: And they think we should be just getting rid of nuclear weapons!

Biello: Or at least working towards a world free of them. They no longer serve the same purpose that they did, back in the Cold War, as we discussed, and in many ways present more of a danger to the U.S. than not having them, and if we can somehow ensure that everybody else also doesn't have them, then this would be the perfect world.

Steve: Yeah! There is a lot of game theory that comes up in these arguments about whether your own initiative in creating them for your defense drives the other side—or the other sides—to want to create theirs and obviously North Korea is playing games with their intent—they are not going to destroy an entire country or certainly not this entire country, so their intent in doing this is obviously to put themselves in a bargaining position for some other purposes.

Biello: Correct. Many think that that's largely aid-related. Assuming that North Korea has a weapon and can threaten South Korea or Japan with it, then that puts us in a position where we need to appease them to some extent. And similar theory holds for Iran; obviously they are under threat from this country and its vast conventional and nuclear arsenals, and therefore Iran might feel that it needs the game changer, known as a nuclear weapon, to protect itself from whatever our designs might be.

Steve: Right and then the reverse works and everybody on this side starts freaking out about Iran's nuclear potential and revs up our program.

Biello: Exactly! Although it's hard to argue that Iran, even if they do create nuclear weapons, will be anywhere near 10,000 any time in the near future.

Steve: So the second question you raise is, what should the U.S. nuclear arsenal be composed of? So what is it composed of now and what should it be composed of?

Biello: Well, as of now, it's composed of what's called the triad, which are the three legs of the nuclear weapons complex, one of which is gravity bombs delivered by bomb airplanes—this was the original way of delivering nuclear weapons.

Steve: "Gravity bombs" is a fancy word, for we drop them, they fall.

Biello: Exactly! And also the intercontinental ballistic missiles, the ICBMs that we all remember from the 1980s and 1970s, and then finally the submarine launched ballistic missiles, which are the ones circling the globe and ready to be launched at a moment's notice. They are also, I guess, viewed as the most effective leg of the triad, and that it would be extremely difficult, if not impossible, to ever render them incapable of being launched …

Steve: Right, and ...

Biello: …because no one knows where they are.

Steve: And then the question of what should the nuclear arsenal be composed of, again you really can't answer that until you figure out what your strategic objective is.

Biello: Exactly! And that's what makes the question of the reliable replacement warhead so vexing, is that whether we need this new potentially more reliable replacement weapon or not depends on what your view is of what our nuclear posture should be and how we should maintain our nuclear weapons complex and all those kinds of thorny problems.

Steve: And the question of replacing the existing weaponry is—it's really a two-pronged question; there is the issue of the aging of the arsenal, but then there is also the issue of just sweeping out obsolete weaponry in favor of new improved weaponry, right?

Biello: Yes, correct. The arguments for the reliable replacement warhead include, obviously, reliability, which is in the title of it, although that has somewhat been put to rest by expert study of the plutonium pets that rest at the center of a nuclear weapon; these are the key items for making a nuclear explosion. Some had argued that they might degrade over time and therefore not explode in the way that we would want them to. Subsequent testing has shown that not to be the case, at least in the opinion of many physicists—many highly respected physicists—and so the supporters of the RRW have moved onto other rationales for why we would need these including margin, which is your, I guess, confidence, that a nuclear weapon will explode as it is intended to; it will deliver exactly, say ten kilotons of destructive force or one megaton or whatever the desired explosive force is.

Steve: Rather than something significantly less than that.

Biello: Right, rather than a dud, as they say.

Steve: So, one of the kind of catch-22 situations is you have funding for the design and development of the replacement weapon, but the funding comes from the other pocket which was the pocket full of money to extend the life of the existing warheads with regular kind of maintenance. So once you do that, then you are locked into a course of action.

Biello: Right, if you allow the existing weapons to degrade beyond a certain point then they, by nature, become unreliable and must be replaced. So, the funding situation that we are in right now—in 1990s, we launched a program called the Stockpile Stewardship Program; it was intended to maintain the existing nuclear arsenal for a number of decades, if not indefinitely and that has been a huge bonus in terms of actually understanding the physical processes of nuclear weapons and getting away from nuclear testing. And in part, the success of that program is what has enabled us to potentially go forward with some replacement warheads and not rely on nuclear testing. But in order to fund, building these replacement warheads, we might have to take away money from this very successful stewardship maintenance program.

Steve: I mean, I realize that we don't have unlimited amounts of money, but when it seemed to make sense to do both at the same time, make sure your old ones are still working, while you create the new ones.

Biello: Well, it depends on what kind of nuclear arsenal you want to have. We are obligated by treaty to reduce our number of active nuclear weapons to between 1,700 and 2,200 and the question is what will compose those 1,700 to 2,200—will it be new, more reliable weapons? According to the Department of Defense, that's how we will make the tradeoff. If we have newer, more reliable weapons then we can have much fewer of them; if we have to have older less reliable weapons, although that reliability question has in large part had been laid to rest, than we would need more in kind of a reserve potential in case some of those ones on the front line failed.

Steve: There is a warning—spoiler alert here—but at the end of the article you raise an interesting point that "perhaps the true rationale for the whole upgrading and improved reliability effort may be to upgrade and improve the reliability of your arsenal of nuclear scientists and technicians."

Biello: That's right. Many of the folks who are involved in building the last round of nuclear weapons or even the first round of nuclear weapons are either passing away or retiring or otherwise their knowledge is becoming inaccessible; and of course there are records, but there is, as many physicists who I interviewed said, "There is nothing like learning by doing and if we want to maintain the ability to build nuclear weapons for the indefinite future, then some argue that we need to continue to build them to train up this next generation of potential nuclear weapon scientists." Of course, there are those who argue that, "Well, you can really get all of that training just by undergoing the exercise of designing a new weapon without actually building it, or if necessary building just one and sticking [it] in the nuclear weapons museum out there at Los Alamos or elsewhere."

Steve: But there are other scientists and nuclear experts, who are very uneasy about a weapon that has never been tested.

Biello: That's right. We have never [to date] employed a weapon that hasn't been tested at all. The argument being put forward currently is that this weapon is largely a composite of older weapons that have been tested and are very well understood. Plus, obviously our computers have advanced by leaps and bounds and we can now simulate almost perfectly what happens inside a nuclear weapon, that being the argument, then there are others who say that, you know, "What general in the field is going to feel comfortable with a weapon that has never been used and therefore has no data as to its reliability?"

Steve: That's a really interesting article because obviously we are still in a transitional phase in, you know, the geostrategic and geopolitical environment. In some ways, the answers to these questions will depend on that environment, and in other ways they will help to shape that environment

Biello: That's right. The choices we make now will in many ways shape our future. So if we choose, to go in the direction of a new nuclear warhead, we may find ourselves with adversaries who have also chosen to go ahead and develop their own nuclear weapons. If we choose to reduce our arsenal to what is viewed by many as a credible deterrent, maybe 300, 400 weapons, which is vastly fewer than 10,000, but would still inflict, you know, horrific damage to anybody foolish enough to challenge us on that front, well then we'll be living in a slightly different world; or we could, as George Shultz, et al argued, "Try to work towards a world free of nuclear weapons in their entirety and put this destructive genie back in the bottle."

Steve: Dave, thanks a lot. I appreciate it.

Biello: Well, thank you for having me.

Steve: And check out Dave's article in the October-November Scientific American Mind magazine called "Searching for God in the Brain'";it's also available at the Web site, www.SciAm.com/SciAmMind

Next up, Karen Schrock; she's one of the editors at SciAm Mind and she spent last week in San Diego at the annual meeting of the Society for Neuroscience. We chatted in the Scientific American library.

Steve: Hi Karen.

Schrock: Hi Steve.

Steve: How are you?

Schrock: Just fine. How are you doing?

Steve: I'm okay. Are you jet lagged?

Schrock: Little bit. But I slept all weekend.

Steve: Good.

Schrock: So it helped.(laughs)

Steve: So you're just back from San Diego; and this is a huge science conference.

Schrock: Meeting [attendance]attendants was about 35,000 people, I believe.

Steve: Thirty-five thousand! How many journalists were there?

Schrock: Not that many, couple of dozen.

Steve: So, it's mostly researchers and their graduate students.

Schrock: Yeah! Sixteen thousand posters! You know, hundreds of lectures.

Steve: That's amazing. Sixteen thousand posters! (laughs) What did you see though that really popped out at you, that you thought was particularly interesting?

Schrock: Well, my favorite, I think, was a report from the University of Bordeaux in France, about rats. Now these rats were given the choice between self-administering cocaine or saccharine, a sweetened water solution, and they overwhelmingly chose the saccharine—94 percent of the rats preferred saccharine to cocaine.

Steve: I would never have guessed that.

Schrock: Neither would have the researchers! (laughs) They were really surprised.

Steve: Now were these rats were they making a choice for the first time or where they already addicted to one or the other?

Schrock: Some of the rats were making a choice for the first time, but they also used rats that were already addicted to cocaine and they actually weaned themselves from the cocaine because they preferred the saccharine.

Steve: Why on earth would they prefer the saccharine, especially when the saccharine doesn't have the nutritional components that sugar really does?

Schrock: Right, good question. They did do this with sugar—with regular sugar—too, with sucrose, and they found a similar result. The researchers think that, you know, the sweetness is producing a reward effect in the brain that's actually stronger than cocaine's reward effect; same kind of dopamine mechanism and the researchers just think this is something biological that the rats are saying, "Hey this is sweet, must be food, must be good for me."

Steve: That's really amazing. So is there any kind of connotation for humans? You know, is this a possible treatment for drug addiction?

Schrock: Well, other researchers—I think there is a group at the University of Minnesota—are looking into the possibility of treating cocaine addiction with other kinds of rewards, so that's definitely an area they are going to look into and they also think it has implications for obesity because if sugar is this addicting and if we can treat it like an addiction, we may be able to curb this obesity epidemic.

Steve: That's really interesting. So how many of the events at the meeting did you actually get to go to?

Schrock: (Laughs) Oh gosh! I don't know. The tip of the iceberg; I mean, I went to dozens and I have so many ideas, but … (laughs)

Steve: All right. So, of the dozens, let's talk about just another few. You mentioned to me earlier, before we started recording, that there were[was] something else from the meeting involving bees and weight loss.

Schrock: Yes, that's right. So, you know, everyone is looking into this weight loss and they are trying to see what the social mechanisms are. There was a big study that came out a few months ago showing that humans are susceptible to this sort of social contagiousness.

Steve: I remember that. So, if your friends all start to put on weight, you'll feel more comfortable putting on a little bit of weight maybe because all your friends are too it, so you are not that much bigger relatively.

Schrock: Exactly!

Steve: You don't really do it in terms of what you used to be, you do it in terms of what your friends are now.

Schrock: Exactly! And so that's a psychological mechanism, but in the bees they are looking at chemical mechanisms, and specifically they found that the queen bee's pheromones will dictate when the worker bees gain and lose weight. So when bees are born, they are very fat and they stay in the hive and they, you know, they do—they tend to the larvae and they, you know, stick around home; then at this particular point in their life cycle, they lose about half their weight and then they go out and forage and they become the worker bees that are out in the field, getting the pollen. So, what happens that the researchers were looking at, this moment, when the bees suddenly lost weight, and they found that it is dictated by the queen bee's pheromones, which trigger this insulin mechanism in the bees' brains that causes them to lose weight.

Steve: So, the researchers are really looking at the relationship between the neurological chemistry and the outcome, because there is no way to mimic that entire behavior for human beings.

Schrock: Exactly! But they think that by looking at some of the chemical basis of, you know, weight loss and/or weight gain, then by manipulating it—and they also look for the genes involved in these chemical signals—then they can possibly translate that into drugs for humans or just understanding better the mechanism of weight loss and weight gain.

Steve: And going back to the cocaine part, there was something else you mentioned to me earlier about sleep loss and addiction that was pretty interesting.

Schrock: Right! A lot of researchers now are starting to tie the really detrimental effects of drug addiction to sleep loss. They think that actually underlying all these sort of memory effects and horrible mood, you know, disorders and withdrawal symptoms are actually the mechanisms of sleep loss; and, you know, having a good night sleep is important for us in so many ways and being addicted to drugs like cocaine or kind of any other drugs will disrupt that, so they found out that actually sleep loss could be the underlying mechanism for lot of these detrimental effects. So in effect, if we could treat sleep loss in drug addicts, we might be able to take away some of the side effects from withdrawal and also curb addiction to some extent.

Steve: Well, that's pretty interesting. That's never been tried, just in terms of, even by accident, maybe sedatives for people who are going through withdrawal?

Schrock: I'm sure that's been tried, but one of the new things they found is this specific tie between the circadian rhythm in our bodies and drug addiction and they found that it is actually through an epigenetic modification of the circadian rhythm; so our circadian rhythms are reset by these drugs; we actually crave them at certain times of day and that is contributing to the necessity to, you know, relapse and go back on drugs or to get that craving, you know, at a certain point.

Steve: That's really interesting too. So, I know that David Dobbs in our Mind Mattersblog recently talked about this next subject, but there was also something that you saw at the neuroscience meeting and that's this issue of empathy. Why don't you talk about that a little—this is a really fascinating study.

Schrock: Sure, so in mice, they recently showed—a few months ago, some scientists showed that if a mouse watches another mouse in pain, its own pain response then is subsequently heightened, so there is this idea of empathy, that when you see another animal in pain, your going to feel pain more acutely yourself. So they wanted to test this idea in humans, so they shot videos of the volunteer's loved ones, spouses, family members in pain and then they showed them to the human volunteers and unfortunately they didn't quite get the response that they were hoping for. The volunteers found the videos amusing (laughs), and thought they were hilarious.

Steve: That's really interesting (laughs); anybody who grew up with the big brothers, nothing funnier than seeing you big brother slip on a banana peel. (laughs) Well, Karen that was really interesting stuff, and you are going to be writing about this.

Schrock: Oh yes! It will be in the issues of Scientific American Mind for the next several months, I think. (laughs)

Steve: Sounds good. Thanks very much, Karen.

Schrock: Right, thank you Steve.

Steve: For more info about the conference and the Society for Neuroscience, go to their Web site, www.sfn.org

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

Story number 1: M.I.T. researchers have created a gel that can change color in response to various environmental stimuli.

Story number 2: Broadway producers are threatening to replace striking stagehands with trained helper monkeys.

Story number 3: The Brookings Institution estimates that the total cost of America's nuclear arsenal has been about $6 trillion.

And story number 4: Space walks are on hold until NASA can figure out why a space suit worn in simulations on the earth has a smoky smell.

Time is up.

Story number 1 is true. M.I.T. researchers have created a gel that changes color in response to temperature, pressure or chemicals. A material in the gel expands or contracts, which changes its overall optical properties. Such a gel could be a quick and easily observable chemical sensor. The work was published in the journal Nature Materials.

Story number 4 is true. A space suit worn in a ground test has a funky, smoky smell, NASA announced on November 13th. As this episode of the podcast went to press, space walks were on hold until NASA figures out why. I'd start with the guy who last wore the suit and see if he smells like smoke.

And story number 3 is true. The total cost of our nuclear arsenal since the Manhattan Project started is estimated at $5.8 trillion. The figure appears in David Biello's article in the November issue of Scientific American.

All of which means that story number 2, about striking stagehands being replaced by trained helper monkeys is TOTALL……. Y BOGUS. But what is true is that monkeys have also gone out on strike. Capuchin monkeys being studied at the Yerkes Primate Research Center were given tokens to exchange for food; those that got vegetables instead of fruit basically gave the researcher the raspberry and engaged in a work stoppage. For more, check out the November 13th edition of the daily SciAm podcastentitled, "The Monkeys are Revolting".

Well, that's it for this edition of the weekly SciAm podcast. Check out numerous features at our brand new, redesigned SciAm.com Web site, including the community, theblog and the image gallery; and you can write to us at podcast@SciAm.com For Science Talk, the weekly podcast of Scientific American, I'm Steve Mirsky. Thanks for clicking on us.