Tuesday, December 26, 2017

Through space and time with a different mind

kw: book reviews, science fiction, multiple genres

I read through most of this book on an airplane from Phoenix to Philadelphia. Sometimes when I fly I work puzzles the whole time in the air, first whatever is in the airline's magazine, then in a puzzle book. I like the books with a great variety of different kinds of puzzles, not just crosswords or Sudoku. This time I began to read right after push-back, and read pretty steadily through most of the flight.

Do you remember Apple's "Think Different" motto of about 20 years ago? They were criticized for not using "Differently", but the word was not intended as an adverb; it was a noun: "Think [things that are] Different". When I first saw it I recalled the century-old NCR/IBM motto "Think". But that one meant "Think [because nobody else is doing it]".

Well, Hugh Howey thinks Different. Though he has published more than 20 novels and novellas, and a passel of short stories, reading the collection Machine Learning was my first exposure to him. I'll make sure it is not the last.

The volume contains short stories and at least one novella made up of short story-length vignettes, in a few SciFi genres. The author supplied endnotes about the stories, of what he was thinking at the time. He'll think inside a character: What is going through the mind of a truly bug-eyed, tentacled alien in a force bent on attacking Earth? ("Second Suicide"); he takes a riff on his friend Kevin Kelly's statement, that when a machine first becomes self-aware, the first thing it will do is hide ("Glitch"); he considers the consequences of love between human and robot (Algorithms of Love and Hate, a 3-story sequence). This last reminded me a little of The Bicentennial Man by Isaac Asimov, but with a very different take on societal reactions. Finally, "Peace in Amber" is the author's memoir of going through 9/11 in the actual shadow of the twin towers (until they fell), interspersed with a truly weird alien zoo story. Based on his endnotes, I think the zoo story was needed to "spread out" the memoir so he could handle the flood of emotions.

The word "gripping" comes to mind. Read the book and see what word it evokes in you.

Sunday, December 24, 2017

Take Tyson's tour

kw: book reviews, nonfiction, science, astrophysics, popular treatments

What's not to like about Neil deGrasse Tyson? He has become the public face of science today. I love his updated Cosmos series. I have privately studied astrophysics and cosmology enough that perhaps I could have passed by his new book, but I couldn't pass by the enjoyable way he treats his subject. Astrophysics for People in a Hurry is well worth anyone's time, whether you know anything about the subject or not...particularly if not!

This is a rather small book, on purpose. Dr. Tyson knows that today's young adults want everything fast, they want it now, and they want it without fuss. If anyone can deliver up a basic survey of astrophysics and cosmology that meets these requirements, he can. He does so in 12 chapters.

When I think of astrophysics, I think mostly of stellar interiors, but there is much more to it than that. Clearly, from the flow of the book, astrophysics includes cosmology in its purview; probably 2/3 of the books content is cosmological. But he really does cover all the bases, from the reasons for roundness (gravity wins), to the shapes of galaxies (the tug-of-war between gravity and angular momentum), and to the reasons for modern cosmological theory to include both "dark matter" and "dark energy". Chapters 5 and 6 present these mysteries as well as I have ever seen, and explain why they seem to be required for the universe to work the way we observe it working.

I had the great pleasure to encounter a professional cosmologist on an airplane flight four days ago, and we had the chance to talk a little (he wasn't in my row, so our time was limited by physical endurance of turning heads rather sharply). I asked him a question I'd have asked Tyson if I had the chance, "If a unified quantum theory requires a quantum of gravity, how can a graviton get out of a black hole so as to interact with the rest of the universe? What is the emitting surface for a graviton?" He admitted that he hadn't thought of that before. After we talked a while of other things, then broke off for a while, he nudged me, saying, "Consider this. A black hole has three qualities: gravity, angular momentum, and electric charge, right?" I agreed. He continued, "The electric charge is carried by virtual photons, the bosons of electromagnetic force. Real photons cannot escape a black hole; that is why it is black. But the electric charge remains in effect anyway. Thus, the virtual photons do escape—and return to—the black hole to keep the electric charge in place." I thanked him for providing a marvelous "hole" in my considerations of gravitons and black holes. I suspect this is the same answer Tyson would give. Now, upon further thought, I wonder if the electric charge is held within the black hole, or remains attached somehow to the event horizon. From there (or very slightly above it), even real photons could escape if needed. But if virtual photons can indeed escape a black hole, then virtual gravitons could also.

This matter doesn't enter into the book. What does enter in, is how all the pieces fit together. Tyson gives us plenty of food for thought. One of my favorites is playing a numbers game with molecules and time. Here is my version of "Whose air are we breathing?":

Part 1
  • The air above 1 cm² of Earth weighs 1 kg.
  • The average molecular weight of air is about 29.
  • Thus each kg of air contains about 34.5 gm-moles.
  • 1 gm-mole contains 6.02x1023 molecules (or atoms) of any substance.
  • That comes to just over 2x1025 air molecules above each cm².
  • The surface area of Earth is 510 million km² or 5.1x1018 cm².
  • Thus the atmosphere contains a bit more than 1044 molecules.
Part 2
  • Our total lung capacity is around 6 liters (with a rather wide range).
  • Our "tidal" capacity, the amount we usually take in with each breath, is about a half liter.
  • That is about 0.022 gm-moles, or 1.3x1022 molecules.
  • An average person breathes about 23,000 times daily, when not exercising a lot, or about 8.4 million breaths yearly.
  • Napoleon Bonaparte lived 64 years.
  • In a 60-year span, the number of breaths would come to about 500 million.
  • All those breaths add up to 6.6x1030 air molecules.
Part 3
  • All the air that Napoleon breathed amounts to 1/15 trillionth of the atmosphere.
  • 1/15 trillionth of one tidal breath is 880 million air molecules.
Conclusion: Every breath you breathe contains nearly one billion of the air molecules once breathed by Napoleon…or by anyone else who has lived at least 60 years! Tyson didn't go into all this gory detail. He names a couple of the figures in a two-sentence riff on the subject. I just went through the figures to work it out for myself, and to share it here.

A particular aim of Dr. Tyson in everything he writes, and says in his programs, is to impress us with the power of the scientific method. We don't learn "how the world works" by guessing. We observe, make tentative conclusions based on observations, argue with others about it, eventually turn the conclusions into a hypothesis that we can test, and then repeat as needed. Now, in cosmology, a "test" would take billions of years. This isn't chemistry, for which you can mix a few things in a jar and take a measurement in a matter of seconds or minutes. Neither is it biology; we have no cosmological Gregor Mendel, crossbreeding stars as though they were peas. But we can work out the math and see how it squares with the things we see.

In science, more than in any other endeavor, "No man is an island." No woman either. The popular trope of the loner in a stained lab coat making a major discovery is simply unknown to real science. Even a few centuries ago, when chemistry was emerging from alchemy and astronomy was emerging from astrology, a "lonely genius" was really a highly social being, surrounded by helpers, colleagues, opponents, and many others. The quintessential scientific loner, Isaac Newton, spent much more time discussing his findings and theories with members of the Royal Society, including friends, "frienemies", and enemies, than he did carrying out observations or even thinking out his theories. Without a helpful gadfly-friend to prod him, he'd never have finished writing his Principia. So although Newton was famously anti-social, he still had to interact socially for his science to have usefulness and meaning. But that's the beauty of science. It is our great, collaborative enterprise of looking back at the Universe that birthed us, to see how it was done, and a great many more things of interest also.

This isn't a textbook. It provides not an education in the subject but a vision of what astrophysics is. If you treat it sort of like a textbook, and write down ideas that interest you as you go along, you'll gather fodder for any further studies you might wish to carry out. That's the kind of thing I've done all my life.

Monday, December 18, 2017

Growing up unique

kw: book reviews, science fiction, space opera, child prodigies

Fiction authors frequently write to explore. I first recognized this while reading one of Isaac Asimov's Robot stories, in which stories he explored the boundaries of the Three Laws of Robotics. He had hinted at them in Robbie and first stated them clearly in I, Robot. Years later I realized he was also exploring the boundaries of neurosis. As I learned of his life, including what he wrote in several memoirs, I understood that he was profoundly neurotic and he used his characters—the ever-more-perfect and godlike robots in contrast to the all-too-faulty humans—to work through the ramifications of neurosis in himself.

I have read novels by Orson Scott Card for about thirty years, beginning with Ender's Game. I don't know if I have read all the Ender series books. I did read all of the Homecoming books, and it is more than clear that in those Card is exploring the boundaries of morality and altruism. His character Nafai is pathologically altruistic.

When I read Ender's Game I wasn't ready for it. I was a mere 40-year-old. I took it at face value, as a coming-of-age novel in a space opera setting. Speaker for the Dead and other Ender series books also left me bemused. Now, just this year, more than thirty years later, Children of the Fleet adds another layer to the Ender saga, and I think I am beginning to understand.

The children in this novel, including the protagonist, Dabeet Ochoa, resemble those in earlier books in that they think rather consistently at an adult level, and perform certain adult tasks, though with some limitations because they are, after all, mostly pre-teens. None has yet hit the pubertal growth spurt, so they wear child-sized space suits, for example.

I was forcibly struck in this novel (and in retrospect, in Ender's Game) that Ender and Dabeet are victims of profound child abuse. Each is massively distorted from what he might have been in a more usual environment. Ender completed his mission, one supplied by others without his knowledge, by becoming the "Xenocide", the one responsible for annihilating the Formics, an insectile alien species. Dabeet's mission is only partly concealed, and he initially conceals it from others. In carrying it out, he brings life, not death (except indirectly, to a couple of all-too-human evildoers), and he prevents massive death.

Rather than dig further into the novel, I want to riff on the meaning of intelligence. We all think we know what intelligence is, but if asked to describe it, none can do so. For a few generations, tests of IQ (Intelligence Quotient) were thought to measure it, but they really tend to measure a small collection of cognitive and memory feats that are more machinelike than I care for. I wonder how the supercomputer Watson would fare on a Stanford-Binet test.

Further, the meaning of IQ has changed over the years. Originally, an IQ test was used with children ten years old and under, to compare their performance with sixteen-year-olds. I don't know how the test was normed (normalized), but apparently youngsters of ages between six and sixteen were tested to establish the "normal" performance of each year cohort. Then higher or lower performance could be compared with these norms to establish an IQ score: 100 for "normal for one's age". Based on the scatter displayed within each cohort, a Gaussian distribution was fitted and a standard deviation of 16 (later 15) was applied. So, when I was given an IQ test in third grade, at age 7, and my IQ score was 170, that supposedly meant that, in the memory and cognitive skills that were measured, I was performing at the level of a 12-year-old (11.9 to be precise). All I knew at the time was that, having begun to learn to read on my own when I began first grade as a 5-year-old (I turned 6 three months later), as a third grader I was indeed reading books usually seen in the book bags of seventh graders.

But how do you measure the IQ of an adult? When I was 20 did I have the "smarts" of a 34-year-old? Does such a question even have meaning? I think not. Others who considered cognitive psychology their calling thought about this quite deeply, and re-normed the test, making the standard deviation (σ) meaningful as a measure of scarcity. Thus, in any Gaussian distribution, the p statistic for ±2σ is 0.9545, or about 21/22. With σ = 15 and a mean of 100, the range ±2σ is from 70 to 130. So if you have a "normal" group of 44 people, one is likely to have an IQ of 70 or less, and one is likely to have an IQ of 130 or more.

I can tell you from experience, though, that IQ has little relation to street smarts. As an adult, my IQ has settled to 160, or 4σ above "average", a level achieved by one person in about 31,000. As a pre-teen and early teen, I finally realized I was not very likable. I began to work toward fixing that. I felt that if I did not have good social reactions automatically, as my age-mates did, I would have to observe, learn, and calculate those reactions. I did so. I used to look at that 170-to-160 shift as "giving up 10 IQ points for a better SQ" (Sociability Quotient). Thus, this paragraph found near the end of Children of the Fleet hit me with special resonance:
Maybe making and keeping friends will always require me to think through the steps of it … Maybe it will never be natural for me, never reflexive, never easy. So be it. I can't live without it, can't accomplish anything without it, so I will become adequate at forcing myself, against my inclinations, to be a friend to my friends. If I'm good at it, they'll never guess the effort that it requires.
Dabeet's musings match mine at just about the same age. Now I'll tell you what happened after I was 40. No details, just this: I had occasion to learn, through a personality test, that my "calculated person" was pretty good; but also, because a part of the test elicited reactions that had to be too fast for my calculations, I learned that a "natural" personality was truly there, and it was also pretty good! I came away with a proverb, "You cannot build a tree." I had found out, after a few decades of tree construction and maintenance, that a perfectly adequate tree had grown up beneath my notice and could be relied upon to be a "me" that didn't need all the effort. I am happier and calmer as a result.

If Dabeet is a reflection of Card's view of himself, as I suspect, maybe he is in the midst of learning, or will soon learn, the same thing. Let's see where the next of Card's novels takes us, and him.

Thursday, December 14, 2017

Bill Nye the Climate Guy

kw: book reviews, nonfiction, scientific method, climate change, polemics

Bill Nye is one of my all-time favorite people. The fact that I was dismayed by some aspects of his recent book doesn't diminish my admiration for him. He is a top-notch science educator and a writer I enjoy reading.

Bill Nye's new book, Everything All At Once: How to Unleash Your Inner Nerd, Tap into Radical Curiosity, and Solve Any Problem, is ostensibly about that middle phrase: "Release your inner nerd." It is primarily an evangelical work, aimed at anyone on the fence between those who "believe" in climate change and the climate-change "deniers". Along the way, though, he offers great examples and advice for many folks who may be a bit tech-averse, to see how humans are by nature technical beings, and that solving problems is what we do best—or we can, if we go about it right.

I hope a great many people will indeed read this book. It is very well written. The author manages to press his pro-climate change case pretty hard without becoming entirely disagreeable. I will address my concerns in a moment.

Let me first state my background in the matter; it is a subject I have followed for nearly sixty years.

When I was a child I heard about the "Greenhouse Effect". It was already old news, because the term was used by Svante Arrhenius in 1896 to describe his calculations that a doubling of CO2 concentration in the atmosphere would raise average global temperature by about 5°C (that is 9°F to us Americans). At the age of twelve I was able to learn enough math to reproduce Arrhenius's result.

In actuality, "greenhouse effect" is not an entirely accurate metaphor. In a greenhouse, the glass physically traps air warmed by the sun, while also providing spectral emissivity to enhance the effect. A "greenhouse gas" cannot physically trap warm air, but causes extra heating solely via spectral emissivity.

The terms "Global Warming" and "Climate Change" began to be used by some in about 1975, and their use ramped up greatly after 1985. "Greenhouse Effect" also took off about that time, when the atmospheric effects they all refer to became a political football. Then a funny thing happened. Looking at the Google Ngram Viewer, I find that since 1992 "Greenhouse Effect" rapidly fell out of favor, "Climate Change" became the term of choice, with "Global Warming" running a rather distant second.

The problem with all this is that "Greenhouse Effect" denotes a possible cause, while the other two terms refer to effects. So now let us back up and examine the term I threw in earlier, "Spectral Emissivity". For solid materials, this refers to a departure from the spectral behavior of a blackbody or graybody. If we could produce a paint that was perfectly gray—at any level of grayness—throughout the electromagnetic spectrum, we could paint it on a surface and it would cause an amount of heating, when the sun shined upon it, directly correlated to the total emissivity. To be specific, a perfect blackbody surface will heat up to a temperature that depends only on the energy being radiated to it. It has an emissivity of 1. A perfect reflector will not be heated at all. It has an emissivity of 0. A perfect graybody surface with emissivity of 0.5 will heat up to an intermediate temperature according to a proportional constant times the Boltzmann factor t4.

Now, consider a "step-spectral" surface. Suppose it has an emissivity of 1 for visible light, and an emissivity of 0 for infrared light. Let's put the cutoff at 700 nm. A surface with this characteristic, in a vacuum so air will not carry off any heat, and with only visible light shined upon it, would heat up until it was hot enough to radiate away that same amount of radiant energy. In visible light it would appear black. It absorbs light, but if it is cool, emits nearly none. Thus it must heat up. You might know from experience that the heating element in an oven gets to about 600°C before it begins to glow reddish, and at 800°C it is getting orange-red. The great majority of its radiation, however, is at infrared wavelengths longer, much longer, than the 700 nm radiation we call "deep red". If it is prevented by the step-spectral emissivity from radiating at those longer wavelengths, it must, perforce, heat up until it is radiating a lot of visible light, to balance the incoming light. Thus a step-spectral surface tends to get very hot indeed, hotter than an oven element.

Now we can consider gases. Oxygen and nitrogen hardly absorb any light at any wavelength of interest to us as we consider the heat balance of our atmosphere. There is a common gas, however, that does absorb a lot of light, at a range of wavelengths that make it a strong greenhouse gas. That is water vapor. Surprised? We will look at some spectra in a moment. First, qualitatively, we find that water vapor absorbs a lot of ultraviolet light, but absorbs even more strongly in several ranges throughout the infrared, with narrow absorption bands at about 1.2 and 1.9 microns, a wider band from 2.5-3 microns, and a wide, almost total absorption feature from 5 to 7.5 microns. The result of this is that if Earth had no atmosphere it would be 32°C (about 60°F) cooler than it is. A perpetual ice age without the ice. So water vapor is by far the strongest greenhouse gas, and is responsible for life being able to exist on earth.

"Climate Change" is all about carbon dioxide (CO2). What does this gas do? It also has spectral emissivity, with an absorption band at about 2.7 microns, a stronger one near 4.2 microns, and a third between 12-16 microns. This last one is of primary interest. It is perfectly placed to absorb about 10% of the thermal radiation from warm dirt, meaning that the dirt has to get a little warmer to radiate that extra energy at other wavelengths. And that is what is behind Arrhenius's greenhouse effect calculation.

Greenhouse gases operate a little differently from painted surfaces. Dirt and other stuff on Earth's surface has spectral emissivity, of course, but not nearly with the perfection of the step-spectral material discussed earlier. So it reflects a lot of light, absorbs some, and gets warm enough to radiate some infrared. In a vacuum, dirt with sunlight shining on it would have some specific temperature. Now put a layer of greenhouse gas above it, an atmosphere containing water vapor. The incoming sunlight is not affected much. But the outgoing infrared from the warm dirt is partly absorbed by the water vapor, which heats up and radiates also, with half going up and half going down. This causes the dirt to get warmer, until it is able to radiate enough to balance its thermal outflow with the radiative inflow from sunlight and also the re-radiated infrared from the warm air above it. How does CO2 modify this picture? It absorbs a little more infrared radiation, in portions of the spectrum in which water is rather transparent. So CO2 strengthens the greenhouse effect. Now, here are the spectra:

I don't know the original source of this graph. It is found all over the place. It also shows a tiny contribution from oxygen and ozone, but we won't consider those here (in the "ozone layer" the temperature goes up significantly, however).

The blue line is for water vapor. The curve marked 255K shows the thermal radiation from a piece of ice at -18°C or 0°F. "Room temperature" is close to 300K or 27°C (81°F). Its radiation curve would be a little to the left of the one shown.

The point is, water vapor reflects back a lot of the radiation from the earth and even from glaciers. Yes, glaciers radiate infrared also. The blue line is for water vapor with a content near 0.3% of the atmosphere, or near saturation (100% relative humidity) at ice temperature. The CO2 curve is for a few hundred ppm; the sources I read didn't state exactly. The result of increasing the amount of CO2 would be to widen the bands, as their "wings" absorbed more and more. This shows what happens when these two gases lead to greenhouse warming.

Now it is a separate issue, whether this is actually causing climate change. "Deniers" say not so, proponents of the idea that CO2 is a "pollutant" say it is. I won't get into that. We have measured that, from the time I was a little child and there was less than 300 ppm CO2 in the atmosphere, and today, when the amount is 400 ppm, global atmospheric average temperature has risen just under 1°C.

Is that a lot, one degree C? Let's look at one factor. Water expands when heated. Heating water by 1°C yields an expansion of 0.000214, or 0.0214%. The ocean averages four km in depth. If the entire ocean were warmed by 1°C, it would be 0.000214x4,000m = 0.856m deeper (33.7 inches). That is enough to force the evacuation of some low-lying areas and certain island nations such as Tuvalu. "Climate evacuation" has already started. But has the whole ocean heated by that much? Not yet. Give it time. The early evacuations were the result of less than one-third of this figure.

I'll stop there. These are not easy points to make with a public that largely doesn't care. Thus, Bill Nye's passion. He wants to make everyone care. But as I read I took careful note: will he mention water vapor? He does not, except for a throwaway phrase in a late chapter. We can't ignore water, for another reason. Trapping a little more heat means adding energy to the system. That means more water could evaporate. Whether it will or not is a huge area of controversy in the climate modeling arena. Water is complex. It might be the most complex substance there is. It is possible that the added energy will yield a net drying rather than adding more water. We might see more rain, or less rain, overall, and nobody yet has a good handle on which areas might experience greater or reduced rainfall. Oh, I've seen a few predictions, but none is well supported by robust evidence.

I agree with Bill Nye, though, that we need to be reducing our dependence on "convenient" energy from burning stuff (mainly fossil fuels), and toward solar, wind and other "alternatives". A generation ago the oil companies began calling themselves energy companies. But they are really still oil and coal and gas companies, with only tiny amounts being spent on non-carbon energy production. They could become the heroes of the 22nd Century. But I fear they will more likely be the goats. I just don't know who else has money enough to do the research to make solar and wind as ubiquitous as they need to become. And there, I think the Science Guy might agree. Read the book. Agree with Bill Nye or not, you're in for a fun ride.

Friday, December 08, 2017

The most popular snails

kw: species summaries, natural history, natural science, museums, research, photographs

For the current series of projects at the Delaware Museum of Natural History, I have worked through several families of terrestrial gastropods (land snails and tree snails). Many of these are quite inconspicuous, being small and not colorful, though they are in general a little more various than the little brown "mud snails" (freshwater gastropods) I worked with for most of 2016.

You know, in any group of creatures, most are rather inconspicuous and poorly known. The "typical" mammal is a "little brown furry thing" such as a mouse, vole, shrew or lemming. The "typical" bird is a "little brown feathered thing" such as a wren or sparrow. The "typical" insect is a "little dark beetle" about the size of a grain of rice. The world is full of little brown things and we hardly notice them.

But we really like the colorful "charismatic" ones. Among the land snails, that would be the tree snails of Florida and the Caribbean, of the genus Liguus.

This is part of a drawer of "unidentified" lots of Liguus fasciatus, the poster child for pretty tree snails. Though these have been identified as to species, L. fasciatus has many "forms" or "varieties", which we provisionally catalog as subspecies, but they probably aren't really subspecies. We usually call them color forms.They hybridize freely, but a particular color form is usually physically separated from most others, being endemic to a few "hammocks", as small patches of raised and heavily vegetated ground are known in the area.

These are mostly from an area of the Everglades called Pinecrest, named for a ghost town tucked away in the middle of a couple of hundred hammocks. You can clearly see that most of these lots are in need of splitting into their color forms. Any particular hammock may be inhabited by a few color forms. A collector in a hurry will gather a couple of dozen shells, put them in a box or bag with a label (date, provisional ID, and location, at the least, to be a useful specimen lot), and move on to the next hammock a few minutes' walk away in the dry season, or a short airboat ride away the rest of the year.

Here is the prettiest of the color forms, in my opinion:

On your computer screen this may be a bit larger than life size. The paper label is 3 inches long, so these shells are about 2 inches long, a little bigger than the average for the species. Liguus fasciatus splendidus Frampton, 1932, must have been Henry Frampton's favorite also. These are indeed splendid! This lot was collected by Erwin Winte a few years after Frampton described them, and in the 1980's it wound up at DMNH.

These shells are so sought after that, though they are prolific and widespread, many color forms are getting hard to find. In the southeast U.S. and the Caribbean, a whole subset of shell collectors are called "Liguus collectors". We are loving them to death!

This only serves to introduce these lovely shells. I hope soon to gather pictures of several color forms, and also to compare L. fasciatus with its sister species in the genus.

Friday, December 01, 2017

Drones fly - monsters die

kw: book reviews, nonfiction, memoirs, soldiers, drones

Brett Velicovich passed by a protest a few years ago. People were wearing or waving mockups of the Predator drone and chanting, "Drones fly, babies die." The colossal ignorance they displayed got through his post-traumatic apathy like nothing had since he returned from five combat tours over more than a decade, in the elite Delta unit, the one that flies the Predator, Reaper and other military drones in Iraq, Afghanistan and other places where the most vicious terrorists operate. He knew what really happens, who really dies, and more importantly, who really doesn't die (that would be most of us! Babies included). He got help from Christopher S. Stewart to write a book about the reality of drone warfare, Drone Warrior: An Elite Soldier's Inside Account of the Hunt for America's Most Dangerous Enemies.

Brett V. was the intelligence specialist on a drone team. He led the work of gathering information and deciding how and when to arrest, of if needed, kill an enemy. After President Obama was elected, the autonomy of the drone teams was reduced, and the President mandated that he must personally authorize each kill, whether by drone or by a raid. I saw a video from late in the Obama presidency in which he was discussing the more than 3,000 killed at his say-so. He said, "It turns out I am really good at killing. I never thought that would be an item on my résumé."

There were, and are, several drone teams. It doesn't become clear in the book how many kills and arrests occurred under the author's purview. But certain numbers stand out, and this one is primary: for every kill there were twenty arrests, and most of them led to useful intelligence. So the 3,000 terrorist leaders whose death was authorized by President Obama are accompanied by the arrest and interrogation of about 60,000 others. That is the key to a war against ISIS and similar enemy groups.

No matter what you think about the use of military drones, you have to read this book. Furthermore, the author portrays unblinkingly what was happening to him. This kind of work leads to estrangement from everyone, from all of us who can never know what it is really like. Every returned warrior is changed. This is still early days of drone war, which changes someone even more than traditional warfare. I hope that can be improved upon.

Mr. Velicovich nearly lost his way after returning to civilian life. He has found something productive to do with his skills. The book ends at the beginning of this new beginning for him. I wish him success in using drone-intel skills for positive things in the civilian sector.