Of Particular Significance

A Couple of Questions for Readers

POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON 11/25/2013

Today I’m looking for insights from readers on two issues that were nagging me over the weekend.

The first issue has to do with the Fukushima nuclear accident and subsequent radiation fears, which I first brought up on this blog last week.   I’ve been thinking about how to write articles that explain radioactivity and radiation in rather plain language, and about what we know is dangerous and what we know is not.  One of the challenges is to confront the extreme irrationality of people’s fear of radioactivity.  I’d like to hear my readers’ opinions of where this fear really comes from.  One explanation of this fear that you’ll commonly read is that “radioactivity is scary because you can’t see or smell or feel it”.  But that makes no sense; you can’t see, smell, or feel viruses either, or low levels of chemicals, so why aren’t people equally afraid of those things?  Especially since the average person is far more at risk of getting cancer or other potentially deadly diseases from viruses (such as papilloma) or from chemicals (asbestos, benzene, etc.) then from radioactivity, despite all the atmospheric nuclear tests in the 1950s and 1960s and the Chernobyl and Fukushima nuclear plant accidents.  So I don’t think this explanation is correct; there are plenty of invisible scary things in the world, and people’s fears are totally out of proportion to the true risks.  I have my own suspicions as to the real causes, but I am wondering what my readers think.

The second issue is more technical. Comet ISON, dubbed, as is typical of our sensationalist age, “comet of the century” before it has even become easily visible [and it might still be a dud, or it might be the best of the year or even the last twenty years; but of the century? check back in 2099!]) is approaching the sun.  There is indeed the tentative possibility, if it survives its very close encounter with the sun on November 28th, that it will give us a spectacular early morning display in December.  In preparation, I’m wanting to read more details about the properties of cometary tails, which are generated by the physics of particles and fields (photons, ions, magnetic fields, momentum conservation, etc.).  [Here’s a nice video of ISON’s tail and its interaction with the solar wind, the stream of charged particles emanating from the sun; also visible to its upper right is Comet Encke, which by chance is also near the sun.  By the way you can also see, watching Encke, that its tail is not a trail; it does not point along its direction of motion but instead points away from the sun.] But I’ve been unable to find anything online other than vague descriptions with no technical information, or references to books or review articles from several decades ago.  Do any of my readers know of a roughly up-to-date technical introduction to the physics of comets’ tails?


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113 Responses

  1. I know this post is ancient, but FWIW here are my thoughts on why people are irrationally scared of radiation. My background is mathematics, so I’m coming at it from that angle.

    People know radiation is dangerous, and can cause cancer, or, in sufficient quantity, radiation burns or radiation sickness. Cancer is one of the most feared illnesses around, so that’s part of it. But, really, I think the irrationality is driven by a failure to understand quantity, magnitudes, and powers of ten, and that this is compounded by our lack of ability to perceive radiation with our own senses, and by a lack of basic information about the amounts of radiation that occur in various contexts.

    The best lay-friendly explanation I know of is xkcd’s. A few minutes of perusing this post makes it abundantly clear that there are natural, everyday sources of radiation that we live with 24-7-365 without any harm: http://blog.xkcd.com/2011/03/19/radiation-chart/

    However, even with this in mind, I’m still mystified by people who have alleged that Fukushima radiation is damaging ocean ecosystems, or making fish unsafe to eat, off the Pacific coast of North America. Maybe these people also lack an understanding of how large the oceans are? Of how many millions of cubic miles of seawater are in the Pacific Ocean? It seems strange to me, but that’s the conclusion I’m led to: Innumeracy.

    1. That’s also why people like to participate lottery and like. But of course, that’s not the whole story in the fear of radioactivity. Fear is contagious and medias are very effective in spreading the disease.

  2. Radiation is invisible, like viruses . . . but from all the evidence of recent history, we can take fairly straightforward steps to avoid the risk of infection. Not so with radiation . . . we can’t easily evade radiation leaked into the environment — or so we believe — and that makes it a much scarier threat. It’s also, potentially, a very long-lived threat: the long-term containment of even relatively localized messes like Chernobyl and Fukushima seems to be beyond our technology.
    And there’s the matter of the number of people put at risk. A disaster that could injure or kill a lot of people grabs your attention, even if it’s a very, very slight risk. It’s a bit like how the same people who worry about commericial airline crashes, which in a typical year kill nobody at all, blithely hurtle down the road in their cars without giving a momen’t thought to the tens of thousands killed in auto accidents every year.

  3. Much of this rationality about irrational fears is precisely what I thought this posting was to avoid. So here are three questions, which should lend themselves to non-philosophical, objective analysis:
    1. Is there any way to extrapolate from the current levels of “background radiation”, what the mutation rate/cancer rate WOULD have been without all the nuclear testing and accidents of the past 50+ years?
    2. At least one peer-reviewed journal reports that the incidence of childhood hypothyroidism in California, abnormal development of thyroid in newborns, can be directly related to the incidence of increased I-131 from Fukushima. Open Journal of Pediatrics, 2013, 3, 370-376 OJPed
    http://dx.doi.org/10.4236/ojped.2013.34067. Can anyone comment on the report’s validity?
    3. Many comments here have likened the large amount of contaminated Fukushima water to be merely ‘a drop in the bucket’, as homogenous mixing in the Pacific would dilute the radioactive contaminants to ‘far below their harmful levels’ (levels which are arrived at by short-term testing and statistical probabilities), but studies from Australia and NOAA/NASA have modeled contamination mixing in the N Pacific gyre which sources the Fuskushima contamination, which indicate prolonged non-miscibility and aggregation. (Marine Chemist seems to poopoo this observation, but I cannot locate any data on the Cullen website to confirm or deny. Marine Chemist: “Between Japan and Hawaii Cs-137 values were measured that exceeded background Cs-137 by a factor of 2-3 and the southeastern leading edge of the plume traveling westward. These levels are not significant when compared with total radiation levels in north Pacific seawater.” Not significant? What is the lower level of no radiation damage? (http://www.globalresearch.ca/fukushima-radiation-levels-will-concentrate-in-pockets-at-specific-us-and-canada-west-coast-locations/5356528) Between the current leak (assuming no further degredation) and a 10+-year window before homogenous mixing and dilution, there will be a 10-year period where contamination WILL be a major constituent of some areas of the Pacific; how can the sea life be told to avoid those regions for 10+ years?

    1. 1) Not directly, but that’s mainly because the effect is so small, compared to the effect of smoking, environmental pollution, etc. that it would be very hard to detect it with reliability.

      2) “At least one peer-reviewed journal reports” — I can’t judge, since I wouldn’t be able to evaluate the study. But I can tell you that until a study is verified by at least two groups, I don’t believe it — and that’s in the context of particle physics, which is a lot easier to get right than is medical research. There are a lot of bad researchers, and a lot of bad studies, in every field. So I don’t consider “at least one” very convincing… as I would not consider it convincing to see one study that claims there’s no effect. If we’re going to make people terrified, we’d better have better evidence.

      3)”“Between Japan and Hawaii Cs-137 values were measured that exceeded background Cs-137 by a factor of 2-3 and the southeastern leading edge of the plume traveling westward. These levels are not significant when compared with total radiation levels in north Pacific seawater.” Not significant? What is the lower level of no radiation damage?

      I can’t respond to this either, in any precise way. However, 2-3 times background of *caesium* does not sound like much to me… the issue is whether it becomes concentrated to a much greater degree, and what that degree is. I agree that is the issue. And regarding “What is the lower level” — there is disagreement about this, because the effect is so tiny that it is hard to measure. However, our bodies have to cope with natural background radiation, so clearly we can handle a certain amount. Why would it be that a tiny bit more has a big effect, when the natural amounts are something we can handle rather well? I don’t understand the logic… the issue is whether there’s a lot more than the natural amounts.

      But you know, you’re being pounded by muons from the upper atmosphere every second. And when you fly in an airplane, that number goes way up. Why aren’t you worried about that? My point is that you’re not using numbers, properly; you’re just throwing them around. 2-3 times background caesium is nothing if the usual background is tiny compared to natural background radiation in total; it’s a lot if the usual background is big. Do you know which it is? I will bet you do not. And I don’t either. My goal is to change that. But the point is: you’re just spreading stuff you don’t understand, and that’s not helpful.

  4. What’s irrational about fearing a technology that has the potential to make vast tracts of land uninhabitable — as it already has twice in 25 years? As current nuclear reactors age, I wonder when and where the next catastrophe will occur. History indicates it will happen again. I hope it’s not upwind of me in Toledo, where workers allowed a hole in the reactor head at Davis-Besse to develop.

  5. As Confucius said, the path to wisdom starts by calling things by their true names. Maybe start by explaining exactly what scientists mean when we talk about radioactivity, radiation and ionizing radiation, and how they relate to one another. I grew up in England during the later part of the Cold War and I seem to remember the phrase that caused fear wasn’t so much “radiation” as “radioactive fallout”, which was further reinforced by Chernobyl. Explaining the role of uncontrolled neutron activation in the wreckage from a nuclear blast versus the very small amount from leaking reactors is something that the Cold War generations could easily get their heads around and that would drive a wedge between visions of post-war Armageddon and the after-effects of an accident like Fukushima. Understanding that precisely what substances leak out of a damaged reactor is important would also help. The difference between the surge of actinides released by Chernobyl compared to the steady trickle of soluble fission products coming out of Fukushima needs to be understood, as does the fact that the main risk from Fukushima isn’t the reactors, which are protected by core-catchers in the event of a meltdown, but the spent fuel pools, which are outside of the main containment and precariously balanced on a badly damaged building in an earthquake zone. The devil is in the details, which few people seem to have understood.

    It seems likely that a few lives will be lost as a result of Fukushima, but perhaps it should be remembered that it was poor planning before the tsunami that led to the accident, the same poor planning that cost tens of thousands of lives from the tsunami itself, far more than the nuclear accident appears likely to take. I guess one source of increased fear that results from radioactivity is what will happen to the people who have been uprooted. Those who lost homes to the tsunami can go home and rebuild their community whereas many of those evacuated as a result of the nuclear accident are unlikely to ever go home and their communities will cease to be. The same thing can happen with huge chemical accidents like Bhopal, but these don’t seem to be any more common than big nuclear accidents and so are easily overlooked.

    The level of regulation and huge expense involved with nuclear energy mean that there is inevitably heavy involvement of government and large corporations, bodies that the public have always distrusted and which are perhaps at an all-time low in terms of public image and credibility. An inflated fear of radioactivity may be irrational, but fear of powerful organizations with an established track record of unfairness, injustice and untruth is perfectly rational. Science has also become so hopelessly politicized in so many areas that a lot of the public are simply turning their back on all of it and will assume the worst when reassured by “experts”, many of whom are just media quacks with an agenda to push. The approach that this blog takes to explaining the science and weeding out the pseudoscience goes a long way towards untangling the mess that I’ve outlined above.

    Irrational fear of radioactivity doesn’t seem to apply everywhere. I live in Hong Kong. When news of Fukushima first broke there was a brief run on things with iodide in them, but within a couple of days everything was back to normal. In post-SARS Hong Kong, it’s fear of infectious diseases that has hit what to me seems like obsessive levels, but then I wasn’t here for SARS.

  6. Not sure why you believe people are more afraid of radiation than of viruses and bacteria. The latter you take precautions against every day by washing your hands, whereas very few people carry a Geiger-counter around (I left mine at home).

  7. I believe the fear of nuclear weapons has been conflated with the risks of nuclear power. This is an interesting and paradoxical result – while hundreds of thousands died in the nuclear weapons blasts at Hiroshima and Nagasaki, these cities almost immediately rebuilt themselves and are home to millions today. Meanwhile dozens died as a result of the meltdown at Chernobyl, but the 1600 square mile exclusion zone remains in effect due to the high levels of radiation.

    It is naive to think that we will, anytime soon, walk away from our energy addiction. It is just as naive to believe that there will be no consequences for the fossil fuels we have been and are consuming. The question is: how do we replace most of our fossil fuel consumption with alternatives in the quickest possible way?

    Solar, wind, geothermal, nuclear – each should be ramped up and made as efficient as possible. There will be future Three-Mile Islands, Chernobyls, and Fukushimas – this is inevitable, but until safer alternatives are developed it’s a price we must be willing to pay.

  8. “Hold the Alpha in your hand, put the beta in your pocket, eat the gamma, and throw the neutron away” – old saying them nucs got-

  9. The distinction between alpha, beta, and gamma radiation, and between short-lived and long-lived isotopes mentioned in some comments above is rather academic and does not match the point when you talk about a real nuclear accident. An event of the Chernobyl type releases all kinds of radiation, and anyone in the path of the fallout and the subsequent contamination path gets a full blend of it.
    It also does not help to say that alpha is harmless unless it is inhaled or ingested. The point is that Chernobyl released contaminated, radioactive fine dust particles that were transported very far in the atmosphere and that then were easily inhaled and ingested. Even once this radio-active dust settled on the ground, the next wind or passing traffic easily lifted it again in the air. Further, the particles entered the food chain, and thereby got into the human body, where they could exert their destructive impact at very short distance. Also, these isotopes have a tendency to concentrate in some organs, creating some hot spots with elevated radiation levels.
    Pointing out that there is a “natural” radiation level does not proof in any way that it is harmless. The natural radiation background may well be a major contributor to the standard cancer rate in a population.
    It is further not adequate to average the radiation level of a nuclear accident over a very large area and then state that this averaged-out radiation level is not high, possibly smaller than the natural background. Experience from Chernobyl was that the fallout was localized in some small regions that were hit by highly radio-active rain. Therefore, some individuals received multiple times the radiation dose of what on average the population in the contaminated area received.

    1. There is a fully operational fusion reactor that will provide us with sufficient energy for millions of years. We use to call it “Sun”.

  10. Not only is there irrational fear about radiation there is irrational fear about nuclear war. What you know, but most people don’t, is that not all radiation is the same. Alpha is basically harmless unless you ingest it. Beta is not much more dangerous and simple clothing protects you. Only gamma is a real threat to humans. But as long as the news media just uses the term radiation this irrational fear will persist. But even some people that should know better are at fault. Look at how nuclear winter is bandied about.

    If you really want to scare people just tell them that they already receive more radiation on a daily basis then they ever were exposed to from all nuclear testing and nuclear accidents combined. And of course a term like half-life confuses most people. Yet few people even realize that you can safely walk through ground zero of a 20MT hydrogen bomb airburst just a little over one month after the blast. The radiation left over from the explosion is almost equal to background radiation by then.

    1. This ” you can safely walk through ground zero …” should be put in the “knowledge” section of the “fab four” (1. Knowledge 2. Identification 3. control 4 Cure)

  11. We do seem to be in a bit of of a dead end in communication between experts and the general public regarding nuclear power. I think it’s a combination of fear of the complex/unknown/”unnatural”/alien to everyday life with an innate suspicion of the reassurances of authority figures. Whilst both aspects might be incorrect and unnecessary, I’m not sure I’d use the term irrational.

  12. Mr. Strassler, one would of course guess that you will find a multitude of reasons all of wich have some merit.

    Some thoughts.

    A virus at least is something that lives. Radioactivity is a nuclear process, not related to human life. Even death by Acid is as a chemical decomposition more related to our bodily functions. So its a fear of something that is not part of our nature, in that sense.

    Also as a critical remark, calling the wisdom of the crowd a prejudice could be considered a prejudice in itself. What you perceive as irrationality could be (at least to a part) common sense. I would not rule that fear 100% irrational.

    Another thought, our rationality and inventions destroy our planet bit by bit. Of course sience is not to blame alone for that, but it plays a part in that picture.

    Radioactivity also represents some of the worst periods on our planet, the cold war and atomic explosions. It is a bad symbol.

    Also as a more general thought, man has always loved to destroy nature because he cant accept nature in itself. And intelligence also is a way to compensate for powerlessness. If I have power, I can control everything, just like I like to control myself.

    So that picture of man would be of a stumbling, misguided search for power and might wich completely disregards what human nature really is about. This intuition is common amongst these that have failed in their lifes, the common man, but rare to people in power.

    So fear of radioactivity is to one part of course irrational because a lack of understanding but on the other hand it also represents a valid concern. I think these both sides are valid at the same time.

    To sum all that up I would just say, radioactivity is feared because it represents our desctructive side especially good.

    Kind regards

    Christian Miersch

  13. I live in Germany, a country that was hit by the fallout of the Chernobyl accident, and I remember very well the months after the public was finally informed about the disaster. I do not share the statement that “people’s fear of radioactivity” is a case of “extreme irrationality”.
    After the Chernobyl accident, it took several days that the German government informed the population that a nuclear accident had contaminated the environment to such a level that it posed a serious threat to the health. The rain was contaminated so heavily that it was well above the radiation limits set by law; the rain would have to be treated as toxic waste (which of course did not happen). The milk produced by cows living outdoors was contaminated to such high levels that it needed to be mixed with milk from other regions far away to reduce the contamination to a level that was considered acceptable, at least for adults. Imagine the situation of parents with small children that need to drink milk several times a day. And it was not just drinking water and milk; all fresh food produced in Western Europe was contaminated. People living in the upper parts of the houses, below the roof, were informed that the rain left its radioactive load in the roof and that they received a higher level of radiation there. There was no way running away from the radiation except if you left Europe; a choice that only few people with sufficient money and no need to care for a family or a job had. Just by the facts, knowing that you receive a level of radiation in various ways that is considered harmful to your health, and no way to escape – this situation causes fear, and I do not consider this fear “irrational”.
    There is also no doubt that the Chernobyl accident and its fallout caused deaths and serious illness. The only point is that with more distance from the Chernobyl site and from the places where the rain caused heavy fallout (in some cases thousands of kilometers away from Chernobyl), there were less victims. The probability that Chernobyl caused deaths and illnesses is exactly 100%. Only if you calculate a probability that you personally get hit by these consequences you end up at some small but still non-zero numbers that may or may not concern you. But in case that you are not only concerned about your personal health but also about your family, your friends, your neighbours, and other human beings that happen to live with you in the same region, you may not consider an event of this type something that does not give you fear.
    The fear about nuclear accidents has the following specific properties:
    – Nuclear plants are man-made, and accidents of this kind could easily be avoided if this kind of power plants were not built.
    – All major nuclear accidents have proven to be essentially uncontrollable. There is no safe and proven way to contain the damage. Once the accident occured, it was a pure question of luck how many populated areas were contaminated.
    – The governments and the operating companies have heavily lied to the public about the extent of the damage and the threat to public health, until after some days it was so obvious that the truth, or at least part of the truth, could no longer be hidden.

    The good news is that after the Fukushima event, the German government decided to phase out the use of nuclear energy, and almost immediately closed some of the oldest and most dangerous nuclear power plants in Germany.

    1. An even better news is that Germany is now importing coal from the USA. Whereas Chernobyl, an insane plant, killed once, coal kills millions every year, and will do much better that way in the future. So definitively, to kill people coal is much better.

  14. I don’t understand that the sun (with solar wind) is located at the right side of the image and Mercury is futher away from the sun ( left side) as the earth is located!

  15. A couple of interesting fact I know I’ve heard but can no longer verify:

    1) Most of the people who died/will die from the TMI accident were or will be killed by the normal operation of the coal and oil plants that had to replace TMI when it was shut down. (i.e. the “nuclear accident” was safer than the alternative energy sources in ordinary use.)

    2) More radiation is released into the environment by coal mining and burning than by any normally operating nuclear plant. (radioactive materials are ubiquitous in nature, when you mine and burn coal, you release radioactive materials into the environment.)

    Wonder if these can be confirmed; or are these questions for xkcd? ; )

    sean s.

  16. One more data point on the public’s misunderstanding of radiation. This morning one of my Facebook friends posted an article on the dangers of microwave ovens, including “unnecessary daily exposure to radiation”. I felt compelled to respond with the difference between ionizing and non-ionizing radiation. I think most people don’t understand the difference and think all radiation causes cancer.

    1. Charles,

      Your comments reinforce mine – the average person does not understand that difference, and the fear-response “of the unknown” drives their response to it.

      Where in our society do we get any standard level of exposure (pardon the term) to the difference? Certainly not from any government publication (“Ions and You – a Love Story”?). Commercial advertising (“Our product has anti-oxidants that trap the free radicals and prevent aging!”)?

  17. Hi,

    Just read any recent writing of Bruce Schneier on security (e.g. “beyond fear”). In short, people are basically driven by noting abnormalities: a tiger in a jungle, that sort of thing. Abnormalities require an immediate response -> fear. What is normal is not treated in the same way in the brain. It’s basically the reason why people fear terrorists (fatality rate ~ very, very small) over traffic (fatality rate much much larger). Note though that government spending is directed towards the first, while arguably directing the same amount of cash towards traffic would be a better trade-of.

    This is amplified by the human propensity to tell stories. Shark attacks make much better, compacter stories than the statistical risks of smoking and are therefore much more likely to stick.


  18. Regarding what GEN says, there is great emotion in China right now about a little girl who died from lung cancer. Lung cancer apparently caused by air pollution. In the USA alone deaths from air pollution caused by fossil fuels are evaluated to at least 200,000 a year.
    Worldwide, this means well in excess of one million dies a year from fossil fuel air pollution. This ought to be always mentioned in connection with the danger of nuclear reactors (none of the civilian nuclear reactors in the USA killed even a single individual).
    Another great fright has been the waste disposal problem, which is much magnified relative to its true extent. And ought to be burned away when mastery of thermonuclear fusion is acquired (as noxious waste could be transmuted away). Thorium reactors have no long term waste (3 centuries at most versus 25,000 years).

  19. Regarding the fears of people towards radiation, there are many images that link radiation to death, specially, a painfull death: Hiroshima and Nagasaki victims, and more recently, the death of Alexander Litvinenko by poisoning with Polonium-210.

    Kind regards, GEN

  20. My take on the irrational fear of radiation:
    It starts at humans’ naturally instinctive interest in information about danger. People collect information about dangerous things in order to be prepared if it comes up to facing them.
    The second step are media which live off human attention and therefore delivery of material about danger keeps their readership interested.
    And the third step are organizations which live off building up human fears which have selected radiation as one of menaces they use. These then look for any signs of radiation (or other) hazard all over the world, send their men to the place with bright yellow suits and large signs screaming “danger” to “investigate”. Naturally they immediately gain attention of media which love delivering this kind of information and that naturally attracts interest of humans watching these media. The circle closes and everyone is happy – people because they got their daily dose of danger, media because they got their daily dose of attention, and organizations because they got their daily dose of donation to “keep up the good work”.
    There are certain topics which keep the wheel spinning. Radiation is one of them.

  21. There are systems of thoughts. There are also systems of moods. The mood towards radiation, nuclear, atomic and the like is drastically bad. To change that, we need to finds the nodes of negativity, and extirpate them like tumors. Honesty and transparency will help.
    For example saying, as some have above, that a nuclear power plant cannot explode is not correct, and thus, not honest.
    Indeed the Chernobyl plant reached in a couple of seconds a power of 100,000 Megawatts, about 60 times what it was made for. At that point, sensors failed, and the reactor exploded in that run-away fission explosion. we have to admit this and explain why it is that no one in the West uses graphite-gas enriched Uranium reactors, because, indeed, at low power, they are highly unstable. Moreover the Soviets, in spite of operating a hyper dangerous, huge power reactor, truly a nuclear bomb in waiting, had not deigned to equip it with a containment building.
    So we have to be honest and explain precisely because how we are going to build power reactors that cannot explode under any conditions whatsoever, including impact with a huge bunker buster bomb. A tall order.
    Another subject that has to be addressed is Hiroshima and Nagasaki. These two bombings were atrocious, indeed. Thousands of little children suffered agonizing deaths, sometimes over years. Many people feel that, as long as there is a nuclear industry, this could happen again.
    However, that position is naïve. Laser enrichment of Uranium, a new technology, can operate in obscure basements. Non proliferation will not be solved by having the great powers renouncing nuclear power, just the opposite. It will be solved by augmenting the knowledge of the subject and the surveillance regime attending to it (the NSA could make itself useful).
    In early August 1945, the top general in Japan was writing poems about the beauty of seeing “100 million flowers been cut”. After Nagasaki, the emperor ordered surrender. the top general tried a coup, but when that failed, he committed Hara Kiri. The entire kamikaze command, disobeying orders, took off in 35 planes, and was never seen again. This is a long comment, so let me simply say that Hiroshima and Nagasaki saved millions of Japanese lives, it not more. A more detailed argumentation will be found on my site.
    We have to dismantle point by point the anti-nuclear arguments. Why? Because only nuclear energy can save the biosphere, while serving justice, paradoxically. See:
    Changing the anti-nuclear mood starts with Hiroshima, and Nagasaki.

  22. Regarding comets: I was surprised to hear in a public lecture by astronomer Dr. Paul Francis (http://www.youtube.com/watch?v=n19HIHCpOVE&list=TLkEaGCXQsZy2-RUAez200Ry9Ima5PP2fO) that there are unsolved problems regarding the direction of comet tails. (He lists it as one of the “Smaller Mysteries” of astronomy.) I do not have a pointer to a technical source myself, unfortunately. You might want to contact Francis – he seems to share your enthusiasm for science communication and comets are one of his research interests.

  23. That link was meant to point to: Gombosi et al. (1996), Journal of Geophysical Research, Volume 101, Issue A7, p. 15233-15252

  24. I don’t know of a recent review on the physics of cometary tails. De Pater and Lissauer “Planetary Sciences” is a standard grad textbook, and has a chapter on comets. Otherwise the intro to technical papers, e.g. http://adsabs.harvard.edu/abs/1996JGR…10115233G might get you started.

  25. With proper care, radiation need not be scary.
    “Radioactivity is scary” because existing reactor designs rely on human operators in the loop to intervene in order not to fail catastrophically; the worst-case consequences of catastrophic failure are widely believed to be, well, catastrophic — lasting for eons, and beyond the state of the art to rectify in our lifetimes; profit-driven enterprises are incentivized to underweight “black swan” risk tails (until reality invalidates their estimates) and to seek successively relaxed relief from oversight by engaging in regulatory capture.

  26. Hi Professor,

    I am a huge fan of your blog and have been reading it for years. I would very much appreciate it if you wrote an article about radiactivity. I’m a surfer in California and I have to deal with a lot of Fukushima drama almost weekly on social media sites. There’s a huge scare over here with seafood contamination and water quality. A lot of people have been reading misleading blogs (mainly the ones that post fear-mongering, misleading pictures such as the tsunami amplitude plots with bolded titles like “FUKUSHIMA RADIATION HEADING TOWARDS CALIFORNIA”). Anyways this fear-mongering is scaring a lot of the surfers and seafood consumers on the West Coast, and it’s mainly from the spreading of completely bogus information (such as articles claiming that scientists say only zero radiation exposure is safe, or that Pacific bluefin tuna are now dangerous to consume).

    It’s not just radioactivity that’s scaring people, but then there are issues like the biological consequences of radioactivity (from low doses), bioaccumulation, biological half-life, etc. People are now scared of nuclear power, radioactivity, and the biological consequences just from all the inaccuracies being tossed around in the media. Just reading “Cesium‐137” scares people now.

    I’ve been following the work of Nicholas Fisher and Daniel Madigan since they’re especially relevant to people living on the West Coast. Here’s some of their works. Of course, this is mainly biological stuff, but it may be something you’re interested in addressing:

    Evaluation of radiation doses and associated risk from the Fukushima nuclear accident to marine biota and human consumers of seafood

    Pacific bluefin tuna transport Fukushima-derived radionuclides from Japan to California

    Fukushima-derived radionuclides in the ocean and biota off Japan

    Natural and Fukushima-derived radioactivity in macroalgae and mussels along the Japanese shoreline:

    Radiocesium in Pacific Bluefin Tuna Thunnus orientalis in 2012 Validates New Tracer Technique:

    Multi-decadal projections of surface and interior pathways of the Fukushima Cesium-137 radioactive plume:

    I’ve only looked at a few of these reports, but here’s a link to many reports on the effects of radiation. I know this is far from your expertise, but this is just in case you want to dive into the topic just a little bit:

  27. The release of radioactive material as a disaster certainly isn’t unique in being a large-scale danger, but I think its special place in the mind of the general public isn’t entirely irrational. There are some things that genuinely set it apart. It’s partially distinguished by its immediacy—it can happen in the blink of an eye, as opposed to something like global warming that takes place over a larger timescale. The degree of harm it can produce is determined heavily by human action, which contrasts it with natural disasters that we struggle to control or even helpfully predict, and that degree of human agency can fuel a sense of mistrust and suspicion of conspiracy on the part of those working to prevent or contain radiation accidents. This puts it in a similar category as pandemics, which are closer to natural disasters but are far more influenced by human intervention and control in a way that fuels paranoia, and especially chemical and other industrial accidents, which are generally similar. However, it is unique both in the potential longevity of the damage it can produce (neither pandemics nor chemical accidents have rendered swaths of land uninhabitable for centuries) and in the frequency of its occurrence, which I think has particularly sensitized the public.

    We haven’t had an acutely virulent pandemic in the Western world since the Spanish flu, and the world hasn’t seen another chemical disaster on the scale of Bhopal. On the contrary, we have seen, in the last seventy years, Chernobyl, Fukushima, Mayak, SL-1, Windscale, Three Mile Island, accidents and contamination from nuclear tests like what happened to the /Daigo Fukaryuu Maru/, a host of criticality accidents, and so on. Chemical accidents haven’t occurred with comparable levels of frequency or intensity. With pandemics, it’s easier to say that our improved knowledge of disease protects us from another 1918 because it was a relatively long time ago, and although we’re definitely concerned about the idea of something like a world outbreak of a weaponized virus, such events remain science fiction. On the contrary, Chernobyl happened less than thirty years ago, and Fukushima is ongoing, so we can’t say with any confidence that we know enough now to prevent such disasters from happening, or keep them from spiraling out of control once they start.

    Furthermore, radiation exposure has its notoriously wide spectrum of possible effects. It shares its insidious invisibility with pathogenic microorganisms, definitely, but disease caused by infection normally has a fairly specific constellation of symptoms, a known course with a few important complications, and so on. Radiation exposure can produce anything from nothing identifiable, to a slight increase in long-term cancer risk, to a marked increase, to acute illness and a high chance of developing cancer within a few years or less, to inevitably fatal acute illness that runs a rapid course. The specific symptoms can also vary widely depending on the material in question and how the dose was absorbed. Radioactive particulates spread readily in air and water over long distances, too, and some take a very long time to decay. All of these factors combined make it dangerously easy to develop a feeling that a nuclear disaster halfway around the world could be poisoning your food, air, and water without you being able to tell, in a mysterious way that produces no immediately identifiable effects but will ultimately kill you in the years to come. This is all true of exposure to certain chemicals too, of course, but again I think fears of such occurrences on a disastrous scale are comparatively lower just because they’ve happened less often.

    Subtle, cancer-causing pathogens like HPVs are, I think, less generally frightening both because they don’t also cause acute, short-term deadly illness or environmental poisoning and because there isn’t much of a question about their presence. Since we know that HPVs are nothing new and common throughout the world, it’s easier to come to the conclusion that they’re not worth worrying about very much because life as we know it clearly goes on anyway and has for millennia in their company, even though deaths from cervical cancer alone in one year outstrip the number of deaths from all radiation accidents in history. Accidental, widespread radiation exposure is an aberrant occurrence that wasn’t an issue pre-WWII, so it’s much easier to feel that it’s hard to say how much of a threat radiation exposure really poses and that it might be far more dire than is usually claimed.

    The secrecy with which many governments and companies have handled nuclear accidents doesn’t help either. From Mayak to Chernobyl to Castle Bravo to Fukushima, there is a trend of cover-ups and efforts to mislead the public, cooperating organizations, and those employed to clean up the disaster, such that we often only understand the true scale of what has happened years later. This makes it easy to worry that there may be nuclear accidents happening in secret, maybe nearby to you, even if there’s nothing in particular to suggest it. It also makes it easy to worry that any nuclear accident that does occur is far worse than you’re being told.

    Greater education would certainly help—for instance, I wish more people understood that radiation exposure can be reliably measured and is only known to cause pathology beyond certain thresholds, which could ameliorate the increase in abortions, depression, alcoholism, and suicide that is sometimes observed in populations that have been negligibly exposed to radiation from an accident. A better track record of straight talk and sober competence from organizations charged with cleaning up radiation accidents would probably do even more. It’s hard to educate people about radiation when there’s such widespread distrust of public officials and scientists around the topic, especially considering that such distrust stems in part from real past and present lies and cover-ups. I have particular sympathy for radiation conspiracy theorists and paranoiacs—their fears may be irrational in their intensity, but it’s hard to blame them.

  28. For me fear of radioactivity is linked to personal memories: I was a kid at the time of the Chernobyl disaster. I don’t remember many details. I recall that suddenly all the grownups became very scared. Maybe we were fetched early from school, I don’t know. I know that we had to stay inside and my parents were listening to the radio. It was a sunny day and we would have liked to play in the garden, but on the radio the told us to shut all the windows and not to leave our houses. I still remember the sight of our sandbox and the grass in the sun as I saw it through the window. It was at the same time a picture of perfect peace and invisible menace. Outside it looked like a ghost town, it felt like the air itself had become dangerous. Everybody was listening to the weather forecasts and afraid that rain would come. They said the rain would be poisonous.

    You also have to consider that this happened during (or after, depending on how you count) the era of the cold war. Even as kids we knew about nuclear bombs and missiles. There were even children’s books about Hiroshima! When I heard military jets flying over as a kid, I sometimes imagined how it would feel like to survive a nuclear blast, but to know that I was condemned to die because of the radiation.

    I guess a lot of people share similar memories (with varying intensity). I think another reason for disproportionate fear is that most people don’t know that natural radioactivity exists, while viruses are something usual that we notice (and usually recover from) all the time. Maybe it would help to educate people about the body’s ability to recover from slight radiation damage? I think the public perception is often that radiation damage to human cells invariably causes cancer. This perceived “absoluteness” and “finality” of the effects of radiation make them more scary than chemical or biological effects.

  29. I think that the fear of radioactivity here in Germany probably originated during the cold war. I was still a kid a mere 30 years ago, but I still vividly remember a general concern at that time that self-inflicted extinction (most probably by nuclear war) was a very real possibility. 1979 was a key year for this topic in Europe – first, the Three Mile Island incident happened at Harrisburg – probably the first one of is kind that got worldwide media exposure. Everybody saw those pictures here over and over again on TV – and there really was nothing to see, which made it all the more remarkable as it was clearly communicated in the news that there was something to fear.
    Later in the same year, the NATO double track decision on intermediate nuclear missiles in Europe caused a big political debate over here that served to heighten the fear of nuclear war. We as kids growing up in 1970s Germany had basically no concept of what war really means, but our parents had experienced one when they were our age and it had left a lasting impression.

    Once you learn to repeatedly associate very bad news with terms such as “nuclear”, “radioactivity” (or even “radiation”) it is likely to stay, no matter where the association originally originated. The Chernobyl disaster in 1986 has strengthened this considerably over here. Unless people are scientifically educated, they are unlikely to differentiate (let alone assess realistic risk levels) between dangers of civil and military use when it comes to anything involving radioactivity. I also suspect that the irrational concern some people display towards radiation from mobile phones may be due to an association of any type of “radiation” with “radioactivity”.

    Add to that the predictable reactions of politics – what has been done to adress this general concern in the population ? It was stated over and over again that serious nuclear incidents are “impossible” to happen in our high-technology countries due to our high standards, making everything “100% safe” and “always under total control”. As a scientist who has worked on basic materials research with possible applications in nuclear energy I was well aware of how to interpret those statements, but the majority public has probably taken them more or less at face value. Enter Fukushima and the current lack of any workable nuclear waste disposal concept, and the trust in any type of “nuclear” technology has dropped basically down to zero here.

    That is not necessarily an entirely bad thing, as the development of renewable technologies has become politically opportune and that will likely accelerate progress that has the potential to open many technological possibilities. Nevertheless, I agree that the perceived danger level in the general population is way out of proportion. So we are in dire need of good science explanations for interested laypeople. I´ll make sure to read any articles you write on this and also point some of my non-scientist friends towards them. Best of luck with this worthwile endeavor.

  30. I don’t think fear of radiation is irrational, other than confusing electromagnetic radiation with ionizing radiation for example.

    Radiation is at the core of the most devastating weapons man has ever created to kill burn and inflict untreatable fatal misery on their fellow man as well as obliterating entire cities. People know that the difference between Hiroshima and more mundane exposure is just a matter of degree. And there is a perception, fair enough, that no amount is entirely safe. More importantly there is no way to feel for yourself when danger is approaching. The first sign you get (the perception goes) is that you have a horrific case of terminal cancer.

    Compare this to heat. We all know how horrible it would be to burn to death. But we can see it coming, feel it getting hot, and try to avoid it. To avoid the dangers of radiation all we can do is take exteme measures against any exposure.

    Education is helpful not sufficient. To allay people’s fear try an experiment like the following… make available an iPhone app (or google glass) that lets people ‘see’ radiation, like weather radar superimposed over everything they see. Red for amounts that are known to cause permanent harm, green for amounts to avoid, yellow for amounts known to harm over long exposure, and clear for levels never shown to do harm. Low levels would then probably be much less feared, similar to cigarette smoke. It’s not just that it can be see, but that you as an individual can use your education plus your senses plus your actions to defend yourself from it. Without those components fear is rational.

    1. Let me make sure I’m making myself clear: fear of ionizing radiation, in the grand scheme of things, is rational, just as fear of driving and fear of mountain climbing is rational. There are potential dangers and it is both rational and wise to fear them. What’s missing is the sense of scale, with the effect that the *degree* of fear becomes irrational. When detectable levels of radioactive atoms show up in fish, people panic — even when the levels are extremely low, and the mercury in the fish is probably a lot more dangerous than the few radioactive atoms that are present. This lack of perspective sounds like a problem that can be addressed.

  31. You say “people can’t see, smell, or feel viruses either”, but people aren’t scared of them. I’d have to say you’re wrong … people have completely irrational fears about unknown viruses. Look at SARS a few years ago, or ebolavirus a few years before that, or the current MERS outbreak in Saudi Arabia. So I’d say that there in addition to radiation being completely invisible, the fact that very few people have any actual experience with it makes it scary.

    1. Hmm. I didn’t say people aren’t scared of viruses… heck, *I’m* scared of some of them, and we all should be. I meant only that the fear of radioactivity is disproportionate. One *should* fear radioactivity, but not at doses comparable to the doses we already get from the natural world.

  32. You may want to mention that sunlight is radiation, and that our species wouldn’t have evolved without it.

    One of the memes that make radiation seem scary to most people is the association with birth defects (post-Hiroshima birth defect photos). This hits home worse than just personal mortality.

    1. I agree; birth defects are a big factor, definitely. Of course some viruses and some chemicals can cause them too (e.g. thalidomide), but they’re a certainty with high doses of ionizing radiation.

      1. My comment about sunlight was intended to reflect that our species has adapted to solar exposure (e.g. skin pigmentation) during our evolutionary history. High energy radiation from radioactive exposure is far less common and consequently our species is unlikely to “adapt” to this type of environmental stimulus.

    2. Radiation is simply “that which is radiated”, and there’s nothing inherently dangerous about it. The question is always: how much energy do the particles that make up the radiation actually carry, and can they transfer that energy to objects that they encounter. Ionizing radiation in the form of high-energy particles that are ejected from radioactive nuclei have lots of energy and often can transfer it efficiently… hence the danger, in large enough doses.

  33. In my area of the country there is a great deal of radon gas emitted from the various soils, mostly granite, but few people seem to be concerned. It seems to be the case that the EPA is more concerned than the people. As far as nuclear power I live about 10 or so miles from a nuclear plant and no one, at least most of us, gives a second thought about it. So, who is against it? Coal plants are far more divisive in the state I live.

  34. Hi Matt,
    I was trained as a nuclear engineer. I went into the field because I was and still am an avid environmentalist. However, the interesting research jobs nosedived after TMI-2, Chernobyl, etc and I moved into another industry. (Similar to HEP grads often needing to find work elsewhere.)

    I definitely think the fear of radiation is overblown, but I also understand that this fear exists even in rational people. My points would be:

    1. Unlike diabetes, heart disease, or lung cancer, one has no control over one’s exposure. A massive dose is like a drunk driver — it injures or kills the innocent.
    2. The uncontrolled release of radiation is like 0*infinity = indeterminate. Very low probability * very high consequence. Your emotions determine which part to emphasize. BTW. TMI-2 had almost zero release to public and Fukishima had low release to public, which will have barely detectable to zero measurable effects on future health. Chernobyl had large release to public (it would be hard to design a more effective radiation release mechanism than Chernobyl — burning carbon in a soot producing environment with lots of fission products).
    3. As mentioned by another commenter, it has always been easy to measure ionizing radiation. Just turn up that gain on the clicking Geiger counter. Historically, it has been much more difficult to measure or detect other potentially damaging substances.
    4. There is a huge difference between detectable radiation levels and medically perceivable effects.
    5. There can be a long period between an acute exposure and the resulting consequence. That’s scary. (What about all that beef I ate in London in the early 1990s — am I going to get Mad Cow?)
    6. Hollywood used radiation as a pretty good creature generator.

    Then there is the controversy about minimum exposure. Some people like to extrapolate the radiation damage vs. exposure curve linearly to zero which implies no safe dose (another 0*infinity thing). Some people reason that since we evolved in low level radiation and our cells seem to be able to repair some damage, there may be a low radiation cut off. (There is even some data that shows radiation workers are healthier than the average population, but I think that’s just because they get an excellent health care package with their job.)

    1. Thanks. Do you understand why it hasn’t been possible to resolve the no-safe-exposure versus low-radiation cut-off debate? This is of course something I have to address in any future writing.

      The “no-safe-exposure” doesn’t seem very plausible to me, given that our species would be highly sensitive to rare spikes in natural radiation exposure if we couldn’t handle something more than the average background; evolutionarily, this doesn’t seem likely, unless such spikes never actually happen. But I see from looking around on-line that “no-safe-exposure” is often quoted.

      1. I do have a cynical reply. Radiation exposure and health consequences to the public during an accident dictate the safety measures that are required for nuclear power plants. Those opposed to things nuclear don’t want to see any relaxation of current rules as their high cost limits the ability to promote nuclear power. The regulators (Nuclear Regulatory Commission) have long held that being overly conservative in one area even though there is some data that would allow them to relax a restriction is OK — just in case they missed something elsewhere. Maybe that’s a good attitude…I would do it differently, though.

        One other point about ionizing radiation. There are alpha particles (a helium nucleus), beta particles (an energetic electron), and gamma rays (high energy electromagnetic). It is easy to shield for alphas (a piece of paper would do, except if alpha-emitter is inhaled or swallowed), not too difficult to shield betas (a piece of aluminum foil). Gammas are like hard X-rays. For low energy gammas the mean-free-path is a few centimeters in water (which effectively zapped a hard to reach benign tumor for me, thank you very much!). For high energy gammas it is centimeters in metal. The amount of damage/ionization is also a function of energy.

        What is the energy spectrum of natural radiation exposure versus plausible radioactive exposure? I don’t know the answer, but I suspect that a bunch of Chernobyl strontium or cesium in your bones is worse for you than some naturally radioactive Carbon-14 or some external high altitude gammas from cosmic rays. The worst actors from nuclear waste in the exposure calculations are those that get readily absorbed in tissue and then decay in those sensitive places.

        It is very difficult to prove that there is a low-radiation cutoff. If one cell dies in a Petrie dish is that the measure? Or, do you have to have to produce noticeable symptoms like hair loss? Much of the dosage limit data comes from epidemiological studies from Japan and (I am guessing) Chernobyl. There are large uncertainties.

        1. Regarding the low-radiation cutoff — do we not have enough data on people who’ve lived in radon-rich environments, lived at higher altitudes, or flown in high-altitude aircraft regularly to compare levels of exposure and see whether it correlates with ill health?

            1. Ok, so then you have to ask: for people who fly 1/10th as often as pilots do, is their risk 1.2X higher [(3-1)/10+1] than the general population, or closer to 1X? Maybe there’s not enough data to tell, but there are a lot of frequent flyers out there. Experimental particle physicists would be a good population, but probably too small…

          1. From SteveB:

            …says that pilots have a 3X higher risk of one type of cataract than the general population and smokers a 2X higher risk. A similar search on skin cancer got lots of hits.

            Can those statistics (ignoring the smoking-related risk) be adequately explained by UV exposure alone? My informal understanding is that cataracts are at least correlated with UV exposure. Certainly some kinds of skin cancer are significantly correlated with UV exposure.

          2. From Marty:
            “Can those statistics (ignoring the smoking-related risk) be adequately explained by UV exposure alone? ”

            The same research showed no additional cataracts for Sun Bathing, so maybe not. Also, how much UV gets through the window material in an airplane? Wikipedia says “Ordinary glass is partially transparent to UVA but is opaque to shorter wavelengths. … Ordinary window glass passes about 90% of the light above 350 nm, but blocks over 90% of the light below 300 nm.”

  35. Why people fear radiation: If there is an unacceptable radiation level in the vicinity where you live, the only way to do something about it is to move. Move from the Chernobyl area, move far from Fukushima.

    Moving is terrifically stressful, especially for people who have lived in the ‘radioactive area’ all their lives. If your lungs are tainted with asbestos, or you fall prey to a virus, at least you are at home

  36. Regarding the fear of radiation, and the comparison with cancer. I think that the fear of radiation and the fear of cancer are exactly the same. In fact, I think if you asked a lot of people, they would say that radiation “gives you cancer”. Both of them seem to us to strike fatally, and there is nothing we can do to protect ourselves. Compare that to viruses and bacteria, which we can protect ourselves from by showering in purell.

    1. There is a lot to that. When I ask people “what is the first thing that comes to your mind when I say the word “radiation”, ” the most common answer is “cancer”. Among the other common responses, though, is “nuclear weapons”. So I would not say the fear of cancer and the fear of radiation are equivalent.

  37. My guess is that people routinely see crawling bugs and their minds extrapolate that unseen viruses and bacteria are something like that. Similarly for pollution, they see smog and soot and they extrapolate to unseen polluting particles. For radiation, they have not seen any macro size object to compare. Actually dentists and doctors are making excessive use of x-rays and more recently cat scans. In these cases health industry has convinced them that they are safe. In your article you might refer to these dangers also. People have seen or heard about nuclear bombs and they associate radiation from nuclear power plants with radiation from nuclear bombs, especially after Chernobyl,TMI and Fukushima. In articles on radiation, one should always compare with background radiation, excess radiation one certainly gets from airplane flights and radiation received in medical (dental) tests and treatments. I think education by writing articles is the only way. You are doing a great job.

    1. This is a very interesting comment — the notion of extrapolating from the known is something I had not considered thoroughly. We do call infectious agents “bugs” (even though they aren’t) and of course we come into contact with chemicals we can see or smell (even though the nasty ones may not be like those at all.)

      But radioactivity *IS* like something we know. Radioactive atoms are just extremely tiny time bombs, which, when they go off, tend to fire out one or two bullet-like particles that can penetrate biological tissues and rip apart nearby DNA and other biological chemicals in our bodies. I was considering using this analogy already; I think you’ve convinced me it is essential.

      1. I’m not so sure that analogy is a good idea. We need to convince people that all radioactivity is NOT the same thing as a nuclear bomb. While you clearly said “time bomb” and not “nuclear time bomb” I’m afraid the distinction would be lost on a general readership.
        It is better to compare a single radioactive nucleus to something else with a lot of kinetic energy. A BB, perhaps, or a pitched baseball.

        1. Ah, very good point; thank you for noting that risk.

          However, while you can compare the emitted particle to a bb or baseball, you can’t compare the nucleus to that. The nucleus is like a loaded gun, waiting to go off with a tiny little “pop”. I still think that you need the notion that the energy is stored in there and can be released at any time, and the notion that the release is more like the mechanical release in a gun than anything else you come across.

          1. I see, yes, I had not thought about how to convey where the kinetic energy was before the particle is emitted.

          2. I fell you’re going astray if you consider analogies rather than comparisons. Kashyap wrote: “In articles on radiation, one should always compare with background radiation, excess radiation one certainly gets from airplane flights and radiation received in medical (dental) tests and treatments. ”

            One significant problem is that people usually get nothing to compare radiation emissions with. An accident may give people a dose orders of magnitude lower than a transatlantic flight, yet that’s usually not pointed out.

            To compound the problem, the distribution of dosage from different accidents is (probably) exponential, so one accident that gets loads of press may give doses several orders of magnitude above another, superficially similar one. A small mistake may also make an order of magnitude difference in the severity of an accident; a completely mishandled Fukushima could have been far worse than Chernobyl.

            Add to this
            – The (political and otherwise) problems with waste disposal
            – Businesses tendency to downplay risk
            – A business model that requires savings for dismantling a plant decades after most profit has been made
            – Potential accidents that makes the company go bankrupt, leaving the cleanup to the government
            – Potential accidents too costly to be covered by insurance that would leave the plant profitable
            – Time scales far too long for political accountability
            – Investments large enough to have “too big to fail” problems
            – Anti-nuclear groups that seldom base their protests on actual numbers

            and people have little reason to trust what they hear from the most vocal sources.

  38. I actually suspect that many people are as irrationally afraid of chemical contamination as they are of radioactivity. This is everywhere in the world of health quackery: there are all manner of products, regimens and services intended to purge unspecified “toxins” from the human body.

    It also figures into anti-vaccination activism (though that does also involve an innumerate downplaying both of the threat of infectious disease, and of environmental chemical threats that far exceed any dose from vaccines).

    1. You are quite right. I know and have known such people and I can trace this to a lack of an interest in a science education, even an informal one. A good general science education is the best antidote.

  39. There are many reasons people have an irrational fear of radiation. One is that they don’t understand it, but that cannot be the whole reason, because there are many other things people do not understand that they are not so afraid of. I think the main reason is nuclear weapons. People know that the least-advanced nuclear bomb destroyed an entire city, and that today’s weapons are powerful enough to destroy civilization. They know that these weapons might leave behind radioactive contamination that would make the area in which it was detonated uninhabitable for many years. Radiation is therefore associated with making the entire planet uninhabitable, which is about the scariest thing most people can imagine. People also see our political leaders treating nuclear weapons as in a separate category of “scary” from even biological or chemical weapons. After all, John Kerry is spending more time trying to prevent Iran from acquiring nuclear weapons than he is dealing with the fact that Iran already has chemical weapons.
    Bottom line: people are really scared of nuclear weapons. Nuclear weapons are radioactive. Therefore people are really scared of radiation because they do not understand the difference between nuclear weapons and radiation.

    The problem is then made worse by the media. They know how afraid the public is of radiation, so any time an incident occurs, they make it a big story (perfectly rational behavior on the part of the companies, by the way). While the Fukushima situation is tragic, there are other tragedies that will result in the death of far more people that will not get the same coverage because people are not as interested. The coverage increases the fear. It is a self-perpetuating cycle.

      1. If you don’t mind me jumping in…

        A nuclear fission reaction is caused by the capture of a neutron in a fissile nucleus. When a U-235 or P-239 nucleus fissions it produces more neutrons allowing for self-sustaining reactions. If the number of neutrons in a system is increasing, the system is supercritical (like a reactor increasing its power); if constant, the system is critical (reactor maintaining a constant power); if decreasing, the system is subcritical (reactor power decreases).

        A nuclear blast is a runaway prompt supercritical reaction limited by the amount of fissile material. It is not all that easy to get this, but basically you need a fair amount of relatively pure fissile material. You cannot control blasts so they are useless for power production.

        A nuclear reactor is designed to never go prompt supercritical. It is designed with a negative temperature feedback coefficient (technically a “negative fuel temperature coefficient of reactivity”), which means that if the temperature of the material increases , the likelihood of fission decreases. So, power increases — temperature increases — power goes back down. It is a pretty classic feedback loop — which one needs to be able to maintain a constant power. The power is tweaked with control rods and/or neutron absorbers added to the coolant. You could rapidly drive the control rods out (for example: http://en.wikipedia.org/wiki/TRIGA) but after a quick power pulse, the system would shut itself down. (There are several other factors in determining the reactivity coefficient, but the fuel temperature is usually the dominant one.)

        One great book that explains a lot of these concepts for the layman is The Making of the Atomic Bomb, by Richard Rhodes. Great historical book, too. Of course, it leans toward the “blast” versus “controlled” fission.

        One caveat, the Chernobyl accident happened because there was a power level/control window in which there was a positive fuel temperature reactivity coefficient. This window was well outside normal operational conditions, but they got there during a test and the accident happened.

      2. I have a lot of experience discussing radiation in public,but not that particular topic.
        What I usually do is try to get people to understand that not all radiation is as damaging as a nuclear blast, which is easier to convey in the one-hour sessions I usually have.
        To be convinced that a nuclear power plant cannot result in a nuclear-bomb type explosion takes an understanding of nuclear power plants. The audiences I speak to usually do not have the background or attention span to get that far in one session. Even if they did, I am not an expert on nuclear power plants. You have an advantage in that you can cover the material in more than one post, so that people can absorb it at their own pace.
        SteveB below seems to have a good understanding.

  40. Hi Mark, I’m a big fan of your posts. Your teaching techniques are a real blessing to us amateur science fans. I’ve put a few articles together for you from NASA.

    Here is NASA’s article on what I think is the most relevant to your question. It is an article about misnamed “Stardust Mission”. http://stardust.jpl.nasa.gov/news/news116.html

    Here is a great overview written for a younger audience, but is factual and from a reliable source http://www.nasa.gov/audience/forstudents/nasaandyou/home/comets_bkgd_en.html

    Here are some other interesting articles about tails. The first one is about our sun having a tail: http://science.nasa.gov/science-news/science-at-nasa/2013/10jul_ibex/

    This is about an astroid having 6 tails: http://www.nasa.gov/press/2013/november/nasas-hubble-sees-asteroid-spouting-six-comet-like-tails/#.UpN8JuB9nHg

    This is about a comet having it’s tail ripped off by a CME: http://science1.nasa.gov/science-news/science-at-nasa/2007/01oct_encke/

    Here is a great picture and explanation of the two types of tails comets have. http://apod.nasa.gov/apod/ap130506.html

    It is my pleasure to assist, Martin Iverson

    1. Thanks! The article on the Stardust Mission is very interesting; I had missed a lot of those results.

      But actually, I’m looking for background suitable for a scientist — something that describes the tails in more technical detail, with discussion of the forces involved and the predicted trajectories of the dust and ions. My longer-term goal is to write something with a little more meat than most of these NASA-style pages.

  41. Look at it this way: the letter R in the acronym LASER stands for radiation. Due to this, the laser is regulated by the government (FDA to be precise – how does that make sense?). While a beam of coherent photons can be dangerous to any eye it is aimed at (or reflected into), beyond eyesight, that beam is well less dangerous than simply standing out in the sun for a while. Yet, we have built a mystique around it. Radiation’s press is the reason for the fear.

    1. I don’t think that’s quite right. One problem is to distinguish “radiation” in general from the high-energy particles in “ionizing radiation”, which is what we’re really talking about being produced in radioactivity. If one uses the word “radiation” without being more precise, it just confuses everybody. The photons in commercially available lasers are visible-light photons, which don’t have enough energy to ionize most atoms, especially the most common ones in biology, and are not dangerous unless you aim very large numbers of them at someone’s eye. Sunlight is more dangerous than normal lasers because it contains ultraviolet photons, with more energy per photon.

      1. Thank you Matt. You are the only one so far to mention that there is a difference between non-ionizing radiation and the ionizing type. In my experience that is where the public needs to be educated. Also, they should be informed that if it weren’t for radiation none of us could possibly exist in this universe because it would be absolutely cold and dead. We live because of radiation just as much as we do because of food and water.

      2. “The photons in commercially available lasers are visible-light photons, which don’t have enough energy to ionize most atoms, especially the most common ones in biology, and are not dangerous unless you aim very large numbers of them at someone’s eye.”
        This statement is incorrect. Visible lasers can also be harmful to eyes and skin for large enough exposure times and large emission levels. Photo-biological safety of the human eye and human tissue is well covered by international standards (for example IEC 60825-1) in a large wavelength range from 180 nm to 1 mm.
        “Sunlight is more dangerous than normal lasers because it contains ultraviolet photons, with more energy per photon.”
        This is also incorrect. Sunlight can be as dangerous as or more dangerous than lasers because of both its ultraviolet and infrared content.

        1. Thanks for setting me straight. Could you clarify, please?

          a) what is the nature of the damage to skin caused by visible lasers? Is it via ionization, heating, or some other effect?

          b) what is the main cause of danger from the infrared light in sunlight?

          1. Dear Matt,

            You have both gotten my point and missed it. My views are decidedly non-average, but they do include recognition of the average assumptions – that all forms of radiation are the same because the average person is not told any different. When a government organization like the FDA is given oversight over lasers because they “emit radiation”, lumping them into the same category as radio-active dyes for internal imaging, how is the average person to know there is any difference?

            While I appreciate your answering my comment in scientific terms, differentiating laser “radiation” from radioactivity, the point is that the average person does not differentiate them, and is reinforced by a 40 year old assumption of responsibility from the government that fails to do so either.

    2. I am remind that Once Upon A Time MRIs were called NMRIs, Nuclear Magnetic Resonance Imaging. But they dropped the reference to “nuclear” because people were refusing to undergo the procedure!

      sean s.

  42. Cold War fears. First use of nuclear technology was a fearsome weapon. Fear of an incurable disease, cancer. Mostly misinformation about radioactivity and how dose is so very critical to how dangerous it is.

  43. I can remember being a teenager in California an my Grandfather asking me if he should vote yes or no on building more nuclear power plants. This must have been around 1980. He was asking me because he knew of my interest in physics. I told him to vote yes. Nevertheless, having been a teenager in the 80’s, I was very much afraid of nuclear war. I can even remember that many of my peers thought it would be a good idea to wipe out Russia with a first strike just because they were that afraid of it happening to us. I can even remember having a dream during a headache I was unaware of that I was looking out over a beautiful scene of green hills and the sun rising when suddenly there was a flash of light and I realized I was seeing an atomic explosion in the distance and I woke in dread and fear.

    So, I agree with those who have said it was the cold war that put the fear of radiation into us. I don’t think so many people would be nearly so fearful of radiation if it had progressed from experiment to power plant skipping over weapons completely.

    I also agree with those who say it has to do with familiarity. People who don’t live in countries where Malaria is common would be fearful to enter a country where it is common, even though people living there think of it no differently than we think of the flu – also deadly of course, but we know everyone who lived through it including ourselves.

    I think even today fear of the HIV virus equals fear of nuclear radiation. This is because it’s incurable and most people don’t know anyone living with it but the news keeps telling us we’re all at risk and that many are living with it without their knowledge. Radiation also seems to be something that could be killing people without their knowledge. I don’t even know if a doctor would recognize that someone’s symptoms were caused by radiation exposure if they weren’t expecting it.

  44. Radiation – In general I think people associate radiation with nuclear bombs and nuclear power plants. They know that in the event of nuclear war between nations, sponsored nuclear terrorism, or major failure of a nearby nuclear plant the radiation that is released or escapes will poison their food and water and they can die of radiation poisoning and/or get cancer. I doubt they give much thought to the particulars…I did see a new book in my local library: “Radiation, What it is, What you need to know” by Robert Gale, M.D. and Eric Lax

    Also saw: “Comets: Creators and Destroyers” by David Levy. However, I have no idea if this book covers comet tails in any kind of detail… (I opted for: “Magnificent Principia: Exploring Isaac Newton’s Masterpiece” by Colin Pask)

    I do know that ISON has pretty much defied expectations so far, being much dimmer than people had hoped coming in, but last week it significantly brightened and is now supposedly visible to the naked eye in the very early morning…time will tell.

    1. Well, ISON’s too close to the sun now, so even though it may brighten it won’t be visible again for another 10 days, because there’s too much sunlight when it’s visible from earth. But come the first week of December, we might get lucky.

  45. May I ask what data persuades you that the general population harbors an extremely irrational fear of “radiation”? Maybe it would be useful to look at whatever studies have been done. There certainly have been studies of people’s concerns about specific issues like the safety of nuclear weapons or nuclear power plants. But those are different from a generalized fear of radiation–or don’t you agree? I was at Pitt when the TMI incident occurred. I recall an engineering prof on TV deriding the fearful response of some people. He said something like “the chances that this malfunction will evolve into a major incident are trivial.” Really? Well, what were those chances and why were they being concealed from the public? People tend to panic when they don’t have an idea of the magnitude of the danger they are being exposed to. How do you call someone’s fears irrational when an accurate appraisal of the risks they face has been concealed from them?

    1. The problem you highlight is a general one. In any risky situation, there are always scare-mongers on one side and experts who are overly reassuring on the other. There are relatively few places where a person can go to hear or read the middle ground, with both optimistic and pessimistic possibilities carefully weighed, without a conclusion but with a serious attempt to look at the possible scenarios. Ideally, the reader should make the final judgment, and the writer should provide the information necessary for that judgment. Of course, a person being interviewed on TV doesn’t have the time to give a balanced view, nor does the typical journalist want such a sensible person on his or her show…

      As for the data that convinces me that the general public has an excessive fear of radioactivity and radiation; I don’t have proper data, so your question is a fair one. I do see a lot of anecdotal evidence on the web, but it’s certainly not scientific.

  46. Like fear of flying, the exaggerated fear of radiation/radioactivity is probably a result of isolated by spectacular events associated with nuclear power. Hiroshima/Nagasaki, Chernobyl, TMI, and now Fukushima.

    That nuclear power is associated with governments and big businesses may contribute to this irrational fear, tho’ tobacco is associated with governments and big businesses too, so that contributor’s effect is more nuanced.

    It’s really quite hard for most people to remain rational in the face of a perceived threat, and often hard to rationally perceive a threat. Hence you will find people smoking cigarettes and terrified of radiation. Go figure.

    Framing a response correctly is critical: if you tell someone that “so many people might die” they will respond to that differently than “so many people will benefit”. Big tobacco successfully fought-off regulation for decades by downplaying the risks and framing the question as a matter of personal liberty.

    Nuclear power is safe (relatively) and contributes little to global warming; reactor designs do need to be improved to keep them safe; the original airplane was dangerous, but modern airliners are very safe.

    Good Luck.

    sean s.

  47. One of the factors that is in play is that is very easy to measure completely harmless radiation levels… Related to this is using units like becquerel that can make such harmless levels sound huge.

  48. Without an irrational fear of radiation, we could have a much safer food supply with a longer shelf life, of especially, ground beef.

  49. Hi Professor Matt.
    Upon self-examination Hiroshima is the personal fear associated with the word radioactivity, I recall reading one witness account noting how a batch of survivors walked through rough rural undulating terrain to escape the city, yet their was an unused main road a few hundred yards away nearby which would have been far more expedient for evacuation, it was the herd instinct whereby people under duress just followed the group to their immediate front. Professor Chomsky of MIT noted how Nagasaki is often overlooked playing second-fiddle to Hiroshima.

    Two comparatively recent Papers exist on arxiv which may be of some help to you (?) in the event you have not previously viewed them:

    -Dr. Karen J. Meech, et al “Outgassing behaviour of C/2012 S1 (ISON) from September 2011 to June 2013.” arxiv.org/pdf/1309.2688

    -Dr. David Jewitt,et al “The extraordinary multi-tailed main-belt comet P/2013 P5.” arxiv.org/pdf/1311.1483

    ……Best wishes and keep up the good work!

  50. I think that two important factors are (1) the fact that radiation is far removed from ordinary experience, and (2) people don’t like to trust experts when their own health is at risk.

    (I admittedly don’t have any sources to back this up–sorry about that. This is based on how I felt before I studied physics and learned what radiation was, so obviously take it with a grain of salt. I’m also vastly over-generalizing when I refer to ‘people.’ I guess I mean, non-experts who are afraid of nuclear energy.)

    For cancer or car accidents, an average person who hasn’t studied science can understand what is happening. Everyone knows concrete examples of people who have experienced those things. They are terrible things, but they are comprehensible and ‘just part of life.’

    When it comes to nuclear power, I think most people simply have no idea what radiation is. People relate to what they have experienced. For most people, the experience with the word ‘radiation’ is: Hiroshima, Chernobyl, cancer, sickness, etc. So it’s a mysterious, man-made threat that is far removed from human experience, but tightly associated with lots of deaths and disease. And I think people also associate ‘getting sick from radiation’ with ‘mutations’–ie, even the diseases seem worse or at least more mysterious than ‘ordinary diseases’.

    I also think there’s a trust issue involved. Cancer is a random event outside of anyone’s control. But radiation from a nuclear power plant is a man-made disaster: if I am a janitor, then I’m being told by a smart engineer that this power plant uses nuclear energy. I ask about 3 mile island–is this really safe–and the engineer assures me that there is a very low risk. So now I have to trust this engineer that he knows what he is doing, and if he is wrong then: Hiroshima, Chernobyl, cancer, sickness, etc. And I think more people are likely to think that scientists in this situation are ‘Prometheus playing with fire,’ rather than sober experts who know exactly what they are doing.

    Now this is a tricky problem, because on the one hand the problem is that people don’t know enough about what radiation really is in concrete terms, but even if we could have every person in the united states be educated by physicists about radiation, it’s not clear to me that it would help. People might misinterpret the ‘education’ as ‘propaganda’. This is understandable in my opinion–since the average person probably has a very weak grasp on the basics of radiation, other than the harmful effects that they have seen from, they have no frame of reference to decide whether they are being lied to or not. The physicist could easily be perceived as a ‘pro-nuclear pundit’ (I don’t think this is an accurate assessment of the physicist’s position, I just think this is how people think). I don’t know how to address this issue, I think this is a very complicated.

  51. As A teenager during Hiroshima and Nagasaki, and following the Concerned Scientists 5 minutes to 12, I might seem fearful. I am not. I favor nuclear power. It is like anything else that can be dangerous, but responsible folks should be able to handle it. The problem is the potentiall misuse by terrorists and the country of Iran. The production of uranium and plutonium should remain under tight controls by the committee of nuclear nations.

  52. I see 2 reasons for abnormal fear of radioactivity amongst common people: first: cold war did it to us. Even if not directly to us, but rather to our parents (ok, I’m old enough to remember that even close to the end of cold war, in early 80’s, possibility of nuclear war seemed to be quite real thing, but some readers are younger than me for sure), but parents usually manage to sell their fears to their children very effectively so it’s the same. Second thing, related to obvious reason, meaning “fear of the unknown and invisible” – ok, it’s like chemicals or viruses but chemicals and viruses are things that people are more aware of, they know that they are everywhere and people are usually aware of their influence. Radioactivity is also everywhere and everyone has contact with it, but most people just don’t realize it at all, and think that the only source of that are bombs or nuclear plant accidents.

  53. I hope you do not mind my answering your second question with another although on-topic question: why doesn’t the comet tail of a comet tail dorado or comet tail goldfish look like a comet tail?

  54. Fear (to radioactivity in this case) grows on ignorance and it is fed for those who use that fear for their purposes. Essentially the phenomena involved are ignored and the effect is augmented by a myth. Something some way similar occurred with “magnetism” in XIXth century. Radioactivity founds its myth in the romantic death of some of its researches due to their work and from the (wrong) guilt of other researches about unveiling a “tremendous dangerous power”(the bomb). States being “owners” of such power said it was more terrific than it was in behalf of the “cause of dissuasion”. You don’t need to be working for the fossil energy industry to benefit from misconceptions on radioactivity , entertainment industry (films mainly) contributed to magnify the fear and the wrong knowledge with it.
    But don’t worry, indeed the main myth/fear of the current century is turning to be “climate change”.

  55. I don’t think the comparison to viruses is that accurate. People have experience with disease; my two-year old is currently getting first-hand experience on the flu.

    Radiation, on the other hand, is something the average person just doesn’t have any experience with (Except in microwave oven and those are not really radiation, they’re microwaves. Branding matters.)

    And finally, people do get upset about viruses. Bird flu, swine flu, …

    Personally, I’m blaming the accidents. Seems like every generation gets a nuclear incident, and they get their fair share of media coverage.

  56. The effects of radiaton to the leaving cell is horrible, hard to believe that you can be cured, no traditional medicine, treatment or whatever black magic is known to cure radiaton. It is not recognized as natural source, only as artificial, man made disease.

  57. I think the extreme irrationality of the fear stems from the connection people make with nuclear weapons and the very rational fear of nuclear warfare. The average man in the street probably believes a nuclear reactor could explode in the same manner as a fission weapon. And of course they don’t know the difference between fission and fusion devices. And of course they’ve seen enough movies touching on nuclear warfare and nuclear power accidents to fuel their fears.

    I’m a former astrophysicist, but know little about comets; a quick search did provide one possible recent reference, only scanned a bit of it, though:
    Physics of Comets, 2010, Krishna Swamy, on Google Books

    Great blog, by the way! Never really studied particle physics, your explanations are very helpful.

    Regards, Stephen Perrenod

  58. I’m nearly 60 & I remember Chernobyl. When I think of the risks of radioactivity I think of it mostly in the same way as lead or mercury poisoning ~ the “bone seeker” strontium 90 for example. I’m aware of the concept of harmful substances concentrating as they go up the food chain & I believe there are many recently introduced man-made substances in the environment which we should keep an eye on. I’m particularly concerned regarding some of the plastics used to package/serve foodstuffs. I regard *radioactivity* as less of a risk than many other new unknowns that we face due to lifestyles, new materials etc. I expect the next big killer will be flu just like in 1918 & in comparison it’s absurd to worry about *radioactivity*. I’m in favour of GM crops/food. I’m in favour of nuclear power.

    Hope that helps!

  59. Yes, fearing an unseen thing might make no sense to you. You are seeing it from a rational pov. This is an irrational situation. It is linked, however accurately or not, to things that also strike fear such as cancer and death. What you write will be seen as sane and true by your readers. Those who fear these things would not likely be swayed.

    Go for it anyway. I want to see what you think.

  60. The extreme dangers of radiation is a well know “fact”. Everybody knows it is the most horrible threat possible to mankind. It is extremely difficult to unlearn something you know for certain is the “truth”.

    It would be an important task to tell people what we really know about radiation, but it is an extremely difficult task to fight a meme so strong as this one.

    1. Extreme. It is extremely dangerous to eat rat-poison. But you can eat a bit without dieing. Indead: I would really like radiation to be scientifically explained. Are you a scientis tyy? Can you do the work ?

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