Why are there so many important numbers?

kw: book reviews, nonfiction, science, numbers, short biographies

A subject that is exercising many physicists and cosmologists is why so many peculiar numbers are needed to define the physics of the Universe, and why they are so seemingly unrelated. Even more, some of them, according to the current theories, need to take rather precise values or the Universe cannot exist, or if it can, it cannot support carbon-based life.

For example, the efficiency of conversion of hydrogen to helium in stars like the sun is very nearly 0.007. (A proton weighs 1.00739 AMU, where the C¹² nucleus is defined to weigh 12.0, and a helium nucleus weighs 4.0015 AMU; 4×1.00739 = 4.02956; subtracting 4.0015 gives 0.02806; dividing by 4.02956 yields 0.00696). Were the efficiency as low as 0.006, to quote James D. Stein, "The neutron and proton would not bond to each other, deuterium would not form, and the Universe would consist of nothing but hydrogen" (We'll get back to the error in this statement later). And were it a little higher, at 0.008, "…it would be far to easy for protons to bond together," and the "big bang" would seemingly have gone on to bang away all the Universe to helium and heavier elements in short order: no hydrogen means no water, and any life that forms would need a different fluid.

Given that nobody has yet determined some tiny (five or fewer) set of really fundamental constants, from which everything else can be derived, we have quite a number of them. The recent discovery of the Higgs boson was supposed to pave the way for a more fundamental physical theory, but that seems about as far off as it did before. My most recent printout of the CODATA list of "important" constants runs to several pages.

The book is Cosmic Numbers: The Numbers That Define Our Universe by James D. Stein, a mathematics professor at CSU Long Beach. Out of the zoo of CODATA constants, he has chosen 13 to explain to us, and even better, he presents short biographies of the scientists whose work led to an understanding of each of them.

Some numbers have dimensions, meaning that their numerical value depends on the system of measurement. Such is Avogadro's Number, 6.0221413×10²³, the number of atoms in 12 grams of the carbon-12 isotope. It is the ratio of the gram to the AMU. By extension, it is the definition for a mole of any substance, where a mole is the weight in grams equal to the atomic or molecular weight of the atoms or molecules. Thus, one mole of pure isotopic iron as Fe⁵⁶ is 56 grams (or, strictly speaking, 55.9349393 grams, because the atomic weight of that isotope of iron is 55.9349393 AMU). Now, suppose instead of grams, we had in history defined a unit mass to be something else, call it a marg, with a mass about 1.66 times as large. Then Avogadro's Number would be, nearly exactly, 10²⁴, and it is likely that scientists would lobby hard to get the marg redefined to make that number exact. Something similar happened fifty or so years ago, when the inch was redefined to be exactly 25.4mm.

Other numbers are dimensionless, such as absolute zero. This is an extrapolated temperature, defined according to the ideal gas law, at which no more heat can be extracted from a substance, and the atomic or molecular motions that define what we mean by "temperature" would cease completely, except for the tiny gyrations needed to avoid violating Heisenberg's uncertainty principle. The "temperature" 0K (K for "kelvins", which have the same size as Celsius degrees), AKA 0R (in which a Réamur is equal in size to a Fahrenheit degree, but the scale begins at absolute zero), needs no units. Zero is zero.

Another dimensionless number is 1/137, the Fine Structure Constant, initially derived from spectroscopy in a magnetic field. Its actual value is 1/137.036 and about six more digits. Though it can be derived from more fundamental constants such as the unit charge and the speed of light, all the units cancel out, so it is the same numerically in all possible systems of units. This isn't one of Dr. Stein's examples. He presents only two dimensionless constants, Avogadro's Number and the efficiency of hydrogen fusion, discussed above. In the latter chapter (Chapter 10), I was surprised at a number of errors that the physicists among his reviewers ought to have caught.

One was the fusion of proton with neutron, mentioned above. Highly energetic P-P collisions are required for the protons to physically approach close enough for one to emit a positron and become a neutron. Then the strong force can take over and fuse the two. The value of actual interest here is the efficiency of P+P→D+e⁺ conversion. A deuteron weighs 2.01355 AMU, so the conversion efficiency is 0.00061. I suspect it is this number, not the 4P→He⁺⁺ efficiency, that matters most. Another error was quite a long discussion of the mechanics of the P-P chain, in which the text uses "electron" instead of "proton" throughout. Electron collisions don't matter in the core of a star. The substance is a plasma. In essence, it is a mass of colliding protons (and deuterons and other nuclei) in a thin soup of unbound electrons, where there is nearly (or entirely) no impediment to P-P collisions except their own positive electric charge. At much lower energies (temperatures up to a few hundred degrees rather than tens of millions), H-H collisions that occur are primarily mediated by interactions between the electron clouds of the H atoms.

OK, gripe over. I confess to being rather staggered by that, but the rest of the book is a delight. We learn, not just the scientific endeavors of Boltzmann or Newton or Boyle, but their lives and something of their personalities. Science is a human activity, and one could say it is the most human of activities: figuring out how things work is our stock in trade (even if we devote our adolescence to figuring out how the opposite sex works!). The beauty of the numbers Dr. Stein has chosen lies in the sheer brilliance needed to first see the requirement for such a quantity, then to ferret out a way to determine what it is. We may see them as obvious in hindsight, but, for example, prior to Newton's insight, a law of common gravitational attraction just didn't fit in anybody's head.

A story is told of Napoleon, challenging his generals to make an egg stand on end. After they'd all given up, he held the egg and rapped it gently on the tabletop, enough to crush the end just a little. Then it stood. One general protested, "Well, that is obvious!", to which Napoleon replied, "It wasn't obvious before you saw me do it."

Does the Devil know he is evil?

kw: book reviews, nonfiction, psychology, evil, villains

The title of this post is a question I like to ask people when the subject of evil comes up. Think of the great villains of history, distant and recent: Athaliah (a genuine evil queen: see 2Kings 11), Herod, Nero, Caligula, Pope Boniface VIII (who "came in like a fox, reigned like a lion, and died like a dog"), Catherine the Great, Lizzie Borden, Hitler, Mao, Stalin or Osama bin Laden. With the possible exception of Ms Borden, each of these persons, and a great many other "meanies", was convinced he or she was good. There's a Crip hit man who wrote the book Monster while in prison. It is his nickname. He likes it. Most of the book is an attempt to convince the reader that he is really a good guy.

Then there's the corner drug dealer/hit man. If you dare, catch up to him and interview him. He'll go to great lengths to show you he's just a guy trying to make a living, giving people a product they want very, very much. I wonder if Earl Bradley, the Delaware pediatrician who raped at least 100 2- and 3-year old girls, thinks of himself as fundamentally good? He even videotaped many of the rapes. What was he thinking?

Flitting thoughts along these lines went through my head when I saw the book I Wear the Black Hat: Grappling with Villains (Real and Imagined) by Chuck Klosterman. I've been hoping to find a book that delves into the possibility that some people actually choose to be evil. The jacket blurb raised my hopes, claiming the book is about people who wanted to be evil. That is as far as it went.

Starting with a discussion of rock bands he hated, the author primarily discusses people who are hated by others, whether or not they actually did anything evil. He derives a rule (we can call it Chuck's Rule of Evil): The villain is the one who knows the most and cares the least. The poster boy for this rule is supposedly Newt Gingrich. Howzatt? His "Contract for America" did more good for this country than any congressional action since. There is no mention in the book of something many folks consider evil, Newt's tendency to have affairs, but wait to file for divorce when the current wife is badly ill.

Klosterman goes on to various other public figures and groups, including a couple of really witless comedians and the rap group N.W.A. (who practically invented Gangsta Rap), and mid-book he discusses sports teams, dwelling on the Oakland Raiders. Now the Raiders' owner Al Davis seems to revel in a bad boy image, with his rule book centered on "Just Win, Baby!". But I suspect, inside, he thinks, "I am such a good coach" (Or thought, since he has now died).

The obligatory chapter on Adolph Hitler, which also mentions Stalin and Mao, really goes nowhere. Hitler is the exception that tests the Rule, because, whether he really knew the most or not, he certainly cared the most. But everything that can be known about Hitler has been written hundreds of times, so all that is left are speculations.

In the end, Klosterman admits that the adage, "he who writes of others writes of himself" is true. The book isn't about whether the hated people he writes about are/were really bad, but about the hatred (or not) he and others feel towards them. We are left with the question, who is worse, the hater or the hated one? In most cases, if there is someone or something you really hate, you'd do well to take a long, thoughtful look in the mirror.

Why the war on terror is an illusion

kw: book reviews, nonfiction, terrorism, crime

Cast a net wide enough, and everyone will be in it. This is the single flaw in Lone Wolf Terrorism: Understanding the Growing Threat by Jeffrey D. Simon. I'll get to that anon; otherwise, this excellent book is a comprehensive survey and diagnosis of a phenomenon that has always been with us, but could become much greater in the future.

We all know what is the greatest terrorism incident in U.S. history: the Sept. 11, 2001 attacks by al Qaeda members in NYC and Washington, DC (the Shanksville, PA crash was probably intended to terminate in DC also). What was the second? The April 19, 1995 bombing of the Murrah Building in Oklahoma City, perpetrated by Timothy McVeigh and abetted by Terry Nichols.

It is hard to imagine a blast that large. I was in Stillwater, OK that day, and I heard the sound. Hearing what it had been on the radio later that evening, my wife and I went the next day to see it. The sight was amazing. So is the thought of a sound heard more than fifty miles away!

Simon introduces three themes:

• The lone wolf is changing the dynamics of terrorism.
• Technology plays a key role in terrorism, and this will increase.
• A lone wolf can me more creative and innovative than a group.

He traces the history of terrorists who worked alone, or with only minimal help, such as the help Terry Nichols gave to Timothy McVeigh in helping him construct the fertilizer bomb. The early examples are primarily assassins, such as John Wilkes Booth. But he includes John Gilbert Graham, the first person to bomb a commercial aircraft in 1955, whose motive was entirely pecuniary; he'd heavily insured his mother who unknowingly carried the bomb onto the plane. This is because he has produced five categories of terrorism:

• Religious – those such as radical Islamists or certain white supremacists who claim a religious motive for their racism.
• Secular (i.e. political) – those such as the assassins of presidents or other public officials, including Timothy McVeigh, and Joseph Stack, who flew a small airplane into an IRS building in 2010.
• Single-Issue – such as those who bomb abortion centers or sabotage logging equipment in old-growth forests.
• Criminal – those who perform terroristic acts for financial gain.
• Idiosyncratic – insane persons, such as schizophrenics or those with "antisocial personality disorder", driven by their delusions to kill or destroy. The Unabomber, Theodore Kaczynski, is included here.

J.G. Graham was a criminal terrorist by this scheme. For that matter, so is the Mafia when its depredations erupt into the public sphere, though they are usually more circumspect in their tactics of intimidation. I find myself troubled by this classification.

I understand his reasoning, to a point. He includes as "terrorists" all who commit acts that cause public terror. If, for some reason, a group of organized criminals had committed the 9/11 attacks, then issued a demand for, say a few billion dollars ransom in return for not doing it any more, is that a terrorist incident? I think not. It is a kind of extortion. There is an entire category of actions for which people who intimidate others too severely are charged with "terroristic threatening", but they are not considered terrorists; they are considered extortionists or other kinds of criminal. So I would deny the category of "criminal terrorist". Otherwise, it will develop into a wide net that includes everyone who goes on a destructive spree, like the guy who blew a gasket and used a tractor to tear down a neighbor's house.

Setting that matter aside, I was (properly) unsettled by his analysis of lone wolf creativity. A loner is not bound to the decisions of a leader or a committee. Thus it was a lone wolf, Bruce Ivins, who first committed bio-terror in the modern era, by sending anthrax spores through the mail in 2001. It is not certain, though, whether his intent was criminal (seeking publicity leading to quicker acceptance of an anthrax vaccine he'd developed) or political (anger at those blocking his research). I wonder if the distribution of "smallpox blankets" among Indian tribes in the 18th Century qualifies as bio-terror, or was it "just" attempted genocide? Simon predicts it will be a lone wolf who first creates havoc with Cyberterror (haven't hordes of virus coders already done that? Most of them work alone).

In the late chapters, Simon turns his attention to ways to prevent lone wolf terrorism—indeed, of terrorism in general—and, failing that, ways to ameliorate the conditions that lead to terrorism. This I find most useful. Terrorism, particularly by small cells and lone wolves, is an arms race between law enforcement agents and the terrorists. For example, it took a generation, but you can now take training courses in defeating a Polygraph. And terrorists are always coming up with new ways to smuggle bombs or bomb-making materials into airplanes and other public venues; the police and TSA and Homeland Security are engaged in a "catch up" race.

I liked the discussion of biometric identification by video, coupled to a hot computer. The way people walk is characteristic, for example. But then I remembered things like putting a tight piece of duct tape between someone's shoulder blades, or taping two of their toes together, to change their posture and gait. These methods are pretty old hat, but could easily defeat a biometric ID scheme.

Simon considers the ways our government and society have aroused ire in others. It is pretty well known, for example, that a lot of Osama bin Laden's hatred for America arose from our cavalier treatment of Muslims and rather open denigration of Islam. But the fire in his belly was because of what he saw as a promiscuous, excessively sinful society. So we may be able to reduce some of the resentment by treating the Muslim countries more respectfully. But what do we do about those who plan to impose Sharia law on the entire world?

By the way, my Islamic friends: this sort of thing was tried by the Christians, several times, most recently by John Calvin in Geneva in the 1600s. It has never worked. The Catholic Church imposed Canon Law for a few hundred years on much of Europe, but it fell apart as people learned more and more about science and psychology. Ironically, much of the impetus for the overthrow of Canon Law during the Enlightenment came from rediscovery of Greek scientific texts that had been preserved by Islamic scholars. The current generation of Sharia promoters are trying to bury the effects their remote ancestors brought about!

I have wondered for a long time, if a society could be developed in which the greatest number of people could develop their genuine abilities and use them to the fullest. Even those we consider unsavory. During the long ages in which European laws required death for a wide range of infractions, kings and governments employed great numbers of executioners. The squeamish need not apply; there were plenty of psychopathic killers whose urges could be in some measure satisfied by such work. I don't know what we would do with people who like to pull wings off butterflies, but such activities are sublimating something else and better understanding of psychology just might ferret out the real motive, and help such a person find a calling that makes him happy without harming others. We Americans claim to believe that the basic rights are life, liberty and the pursuit of happiness. While it is foolish to believe we can help absolutely everybody actually to achieve happiness, it is worthwhile striving to achieve the greatest good for the greatest number.

Yet a very good society, were it achieved, would not eliminate terrorism, either by groups or by individuals. "There is no pleasing some people." So the continuing "war on terror" is actually a branch of criminal jurisprudence, where the action is domestic, or of international diplomacy. Overcoming criminality, including terrorism, is a permanent game of Tetris. The blocks keep falling, and you never quite get them all. And I remember a saying from the Vietnam War: "It is costing us a quarter million dollars for each Viet Cong we kill. We could pay them off for less than that." Is it too crazy a notion to think we can just bribe most of the potential terrorists? I mean, we could have BOUGHT Viet Nam for what the war cost us.

Yeah, I know, the ideologues and single-issue (e.g. anti-abortion) folks will never be satisfied. But a happier society would go a long way toward removing two or three of the five categories above. Worth thinking about.

Sometimes it is just easier to walk

kw: book reviews, nonfiction, air travel, airline industry

I first rode an airplane in 1953, aged 5. I barely remember it. I am told it was a DC-6. At a cruising speed of 270 kts (311 mph or 501 kph), it would have taken about 2 hours to fly from Los Angeles to Salt Lake City, assuming it went straight through. I probably slept through most of the flight.

I sure wish I could still sleep on airplanes. In my longest ordeal, we flew a 3-leg flight: Tokyo Narita to LAX, then to Dallas, then to OKC, where a friend picked us up for the drive home. I didn't even sleep in the car, nor during the layovers. Starting when my wife's brother drove us the 3 hours to Narita, 2 hours before flight time, I was awake and in one way or another on the move for 24 hours. My wife and our son did get some sleep. I am glad we weren't returning from Sydney! After that trip, I began to say, "The worst part of travelling is the travel." And this was years before 9/11! Security check-in was "show your ID and walk through", family members could sit with us at the gate until boarding, and there were real meals on board two of the flights.

Well, I won't go on about what has changed. That's the job of Mark Gerchick, in his new book Full Upright and Locked Position: Not-So-Comfortable Truths About Air Travel Today. He has been in the industry all his career, including some time as chief counsel to the FAA.

The author might have provided us a checklist of discomforts that now accompany air travel – and this would  be an even bigger book! Instead, he has focused on the important stuff, such as our changing status, from "guests" or even "clients" to "self-loading cargo"; or the tremendous economic effect of the steep rise in fuel cost plus a global recession, a double whammy that is still being ironed out.

You don't need me (or him) to tell you that even "business class" is less comfortable then the "coach" seats and service of the 1960s and '70s; that it might be better to be anesthetized upon arrival at the airport, and awoken at our destination (except we wouldn't be self loading any more!). But after going over all the changes of the past half century, he is actually hopeful that things are getting better. For example, newer planes, built of carbon fiber more than of aluminum, and thus more resistant to repeated stress, can house a higher cabin pressure and a bit more humidity. The airline keeps the pressure low, not so you'll be too groggy to make a pass at the attendant, but because an aluminum airframe develops cracks much more quickly if the pressure is like Denver's altitude rather than Nepal's. There is a bit of hope that airplanes will back off a little bit from being "flying buses".

And there are things that are better than before. Unless you are a total computer-phobic, online ticketing and online check-in really reduce the hassle we used to endure to get tickets and boarding passes. Imagine all that added to modern TSA procedures! We would need to arrive 3-4 hours early instead of just 1½ or 2. But our Internet advantage when finding tickets is eroding. I have noticed that Southwest was the first of several airlines that don't fully cooperate with Travelocity or its clones any more. You want the best deal, you go to their own website. That means I have 4-6 tabs open when I am looking for a flight. And I have to read a lot of fine print to unravel the surcharges and extras. It is an arms race.

Mark Twain said, "Everybody complains about the weather, but nobody does anything about it." We actually have better control over the airlines than we do over the weather. They do depend on our good will to stay in business. So there is hope.

Countering the China syndrome

kw: book reviews, nonfiction, radiation, radioactivity

A couple of years ago, in answer to fears expressed by friends and relatives, I posted Uranium 101, to explain what we should fear and what we should not fear, about Uranium and the possible release of radiation in Japan after the earthquake and tsunami.

I am gratified to read a comprehensive summary and explanation of these matters in Radiaton: What it is, What You Need to Know, by Robert Peter Gale, M.D., and Eric Lax. The authors discuss the sources of background radiation, and the things we do that add extra radiation exposure, such as getting X-rays and CT scans, flying, and smoking. That's right, smoking increases exposure to radiation. Tobacco plants do not take up uranium from the soil, but the "daughter elements" radium (4 million times as radioactive as uranium) and polonium (5,000 times as radioactive as radium) do get into the tobacco leaves, and into cigarettes. If this really worries you, but you can't stop smoking, do this: the half life of polonium is 138 days, so just stockpile your smoking materials, write dates of purchase on the packages, and don't use them for 4 years. Then the polonium content will be less than 1/1000 of what it was when you bought it.

OK, back from digression. Americans living at sea level are exposed to 3-4 mSv (millisieverts) of radiation yearly. Higher elevations take us above some of the protective atmosphere, so nationwide, the average is about 6 mSv. When you fly in a jet plane at 36,000 ft, you are above 3/4 of the atmosphere, so more space radiation reaches you. However, now you are shielded from most of the radiation coming upward from the ground. Still, you receive a lot more radiation during each hour of flight than you get from the X-ray backscatter scanner at the airport. Better news: many airports are replacing the X-ray scanners with T-ray scanners, which cannot cause harm.

Many people are afraid of all kinds of radiant energy. The electromagnetic spectrum is very, very wide, and only about half of it (in logarithmic terms) is harmful. Too see how wide, we need to talk units. Two sets of units are used, wavelength and energy per photon. Wavelength is used for the longer, less energetic photons, and energy is used to discuss the higher energy, very short-wave photons. The "center" of the spectrum is visible light, and in this region, both units are used depending on the reason for discussing them. So let's start with visible light, and the near-visible regions of near infrared and near ultraviolet.

The limits of normal vision are considered to be at wavelengths of 400 nm at the blue end, and 700 nm at the red end. Actual visual response at these limits is about 0.4% of the response to yellow light near 580 nm. The unit nm is the nanometer, or a billionth of a meter. To convert to energy, the proportionality constant is 1,293.7 eV-nm, and we divide this number by the wavelength to get energy. So blue-limit light's energy per photon is 1,239.7/400 = 3.1 eV, and at the red limit, it is 1,239.7/700 = 1.77 eV. The eV is the electron-volt, the energy an electron has when accelerated by a 1-volt potential. Old CRT type TV sets used an electron gun with about 30,000 volts, so the electrons were hitting the front plate with an energy of 30,000 eV, usually shown as 30 KeV, for Kilo-eV. We'll get back to this.

Near-infrared (NIR) is typically considered to range from 700 to 5,000 nm, AKA 0.7-5 µ (microns; the "consistent" term micrometer hasn't really caught on). Near-ultraviolet (NUV) ranges from 400 to 280 nm, the range of UV that can easily pass through the atmosphere. It has two components, UVA and UVB, with a cutover at 315 nm. UVC that you may have read about is the germicidal UV used in hospitals, ranging down to about 240 nm, where the atmosphere blocks it even over short distances, such as across a room. The UVA-UVB cutoff has an energy of 3.94 eV. Organic chemical bonds have energies in this range, which makes UVA and UVB risky for our skin. The thinner ozone layer is letting through a little UVC from the Sun, also, which is why sunblock is needed more now than in the past. The energy of UVC is at least 4.43 eV per photon, and it can damage exposed skin quickly.

Energetic as these wavelengths may be, they are not ionizing radiation. That takes a lot more energy per photon. Although the C-C bonds in organic materials can be broken by UVC, that produces free radicals, not ions. True ionization needs at least 10 eV/photon, or a wavelength shorter than 124 nm. This is the boundary between Far UV and "soft" X-rays. The X-rays used by your dentist are generated by an electron beam hitting a tungsten anode at 70,000 volts. They have a range of energies peaking at about 40 KeV. These are called medium X-rays, while hard X-rays are in the range above 100 KeV. Such X-rays are used by industrial inspection X-ray machines.

Remember the CRT TV? It produces small amounts of rather soft X-rays at about 20-25 KeV. That's why parents used to tell their children to stay farther from the TV set. Today's flat-screen TV's, whether Plasma, LCD or LED, do not produce any X-rays.

Now, how about your cell phone? Can it cause cancer? While you are talking (not listening), the phone is signaling to the tower using about 1 watt of microwave radio. While "microwave" may sound scary, that just means it is at a wavelength shorter than the UHF band used for analog TV signals (channels 13-65), in the pre-cable days. Microwaves have wavelengths over a wide range, from 1 m to 1 mm. Let's convert the shortest wavelength (most energetic) to nm and check the eV formula: 1mm = 1 million nm, so 1,239.7/1,000,000 = 0.0012 eV per photon. This is much less energetic than visible light. You'd suffer more damage by shining a flashlight into the side of your head! By the way, T-ray scanners use a wavelength near 1 mm.

Other kinds of radio use even longer wavelengths, and their tiny photon energies are why this unit is not used in this range. The longest common frequency to which we are exposed is the 60Hz signal from AC power transmission, which has a wavelength of 5,000 km. Thus the range of non-ionizing radiation is between 5,000 km and about 500 nm, a range of 1 quadrillion to 1. Now let's look at higher energies than X-ray.

There is a big gap in the spectrum of natural radiation to which we are exposed, because of blocking by the atmosphere, and because common radioactive elements produce energetic particles starting at a rather high point, though typically at a low level. Three elements form the foundation of natural radiation in Earth materials, mostly rocks: Uranium, Thorium and Potassium.

First and foremost, we cannot avoid Potassium (symbol K). The human body contains 0.25% K. Thus, I weigh 200 lbs (91 kg), so my body contains half a pound of potassium, or about 0.23 kg. The radioactive isotope of potassium is K-40, and makes up 0.0118% of the total, or 0.027 g; just over 1/40th of a gram. That isn't much, and K-40 is weakly radioactive, with a half life of 1.28 billion years. But that 40th of a gram is about 4x10²⁰ atoms, of which nearly 7,000 decay each second. Now we get to energy. K-40 decays by the beta process, ejecting an electron or positron (it can do either, to become either Ca-40 or Ar-40, both of which are stable). The ejected particle has an energy of 1.3 or 1.5 MeV (million eV), some 1,000 times as energetic as a hard X-ray. It also produces energetic photons with an energy of 0.5 or 1.5 MeV. The beta particle stays in the body, while the gamma photon can exit, meaning that during a hug (or sleeping together) we receive some gamma radiation from our partner!

K-40 gamma radiation is near the low end of the range of natural radioactivity, but is not the lowest. Uranium and Thorium in the soil, particularly in areas with a lot of granite, produce energetic alpha particles, but these are absorbed by almost anything, such as a sheet of paper. A typical room with gypsum sheetrock contains a tenth of a gram of U and half as much Th, but their alpha radiation is stopped by the paper and the paint on the wall. Not so their gamma photons, which are actually in the hard X-ray region, at 48 KeV and 59 KeV respectively. Also, they have long half lives, 1.41 billion years for Th-232 and 4.51 billion years for U-238.

What about Radon? When U-238 emits an alpha particle, it becomes Th-234. That emits a beta particle (24 day half life) to become Pa-234 (Protactinium), and the chain continues. After a few more decays, Radium (Ra-226) is produced, which has a half life of 1,600 years. After an alpha emission, the next daughter element is Radon, specifically Rn-222, with a half life of 3.8 days. This is a gas, and is a concern everywhere there are soils derived from granitic rock (most of the U.S.). Radon is the primary cause of lung cancer in nonsmokers. Although it produces gamma radiation, with an energy of 500 KeV, it is the 5 MeV alpha particle, with nothing to stop it, that damages the lung. In sum, the ionizing range of radiations goes from about 10 eV to about 10 MeV, and there are cosmic rays with much higher energies. This is about a million-to-one range, a much smaller part of the entire spectrum than the non-ionizing range.

All this, a combination of salient facts from the book plus things I knew or dug out of the literature, set the stage. When you put everything together, people worldwide experience a background radiation level of 2.5-8 mSv. That is a combination of exposure to K, U and Th in soils and rock, to Rn in the air, to Ra in some rocks, and a contribution from solar radiation more-or-less blocked by the atmosphere and depending mainly on the elevation above sea level. That unit, milliSieverts, is a complex measure of the potential damage from ionizing radiation. The radiation of your cell phone is ZERO mSv, because it is not ionizing. A dental X-ray is in the range of 0.005 mSv, or about 0.1 mSv for a set of 18 over your full mouth. If you live in Florida, with little granite, and your background exposure is 3 mSv, you'd have to get 30 sets of dental full-mouth X-rays in one year to double your dose. Of course, that is skewed because most of it would be to your head, particularly if the dental technician puts a lead shield on you like mine does.

CT scans are another situation entirely. A chest-abdomen spiral scan totals 50-60 mSv, equal to 5-10 years of background radiation for most of us. This is the greatest radiation exposure most of us will ever have. When your doctor orders a CT scan, make sure it is for a good reason!

The authors of Radiation dwell much on what was learned from the casualties and survivors of the Hiroshima and Nagasaki nuclear explosions. This sets another baseline, the high end of survivable exposure. The LD50 (lethal dose for 50% of victims) for whole-body radiation dosage is 5 Sv or 5,000 mSv. That's only about 100 CT scans! However, that is a single-event dose; little is yet known about doses spread over years or decades. It seems the body can repair radiation damage up to a point.

The authors stress several times, when a doctor prescribes any kind of radiation beyond a simple X-ray, you need to ask what the exposure is, as compared to background (stated in mSv or in milli-Grays, which is equivalent). If the doctor can't state that, or won't, you need a different doctor! The doctor also should be able to explain the expected benefit and how it outweighs the risk of the radiation dose, whether from a CT scan, radiation applied to a cancer, or an ingested or injected radioisotope for some therapeutic or test purpose. This is a general rule, but is particularly important regarding such therapies and tests: if your doctor can't or won't explain, get a new doctor!

Finally, I have to tout nuclear power generation. The authors make it clear that we are much more likely to get radiation-induced cancer from coal burning power plants than from nuclear power plants. There are radioactive elements in coal, and they go right into the air when coal is burned. Also, the slag remaining from burnt coal contains heavy metals and other toxins, and these don't have a half-life like U or Ra, so they are toxic forever and ever. A nuclear power plant produces a few tons of high-level radioactive waste per year. A coal fired power plant produces hundreds or thousands of tons of toxic waste per year. The waste dump for a single coal plant could be used to store all the output from all U.S. nuclear plants for decades or centuries, and not run out of room. Just put the canisters on pallets on the ground, fence it off, and guard the stuff.

Really, we ought to be recycling spent uranium. 95% of its energy is still in there, just "poisoned" by the fission products. The problem isn't scientific; the science and technology are well known and safe. The problem is political. Even better, we ought to be using breeder reactors, to turn U-238, which won't "fizz", into Pu-239, which will. There's 140 times as much U-238 as there is U-235, the usual fuel. I suggest having the U.S. Navy oversee the design, construction and operation of nuclear power plants. They've been running aircraft carriers and submarines with nuclear power for more than half a century, and they seem to be able to do it without meltdowns or other accidents.

OK, I really like this book, and got quite inspired as you can see above. Without minimizing or distorting the risks, the authors make it clear that current fears about radiation are unfounded. Knowledge is the enemy of unwarranted fear. This book belongs on everybody's reading list.