This is a project I've been playing with off and on since Isaac Asimov's centenary a couple months ago. Even with other duties, I find I now had the time to finish it off.
Asimov's favorite writing was the science column he wrote monthly for The Magazine of Fantasy and Science Fiction from 1958 until his final illness in 1992, totalling 399 columns. It was a continuation of a column he'd begun for Venture Science Fiction, F&SF's sister magazine, earlier in 1958, and transferred to F&SF when Venture folded, so by that count there are 403 columns.
Doubleday published a selection of columns as a book in 1962, and successive books cleaned up some of what had been missed. By 1966 Asimov was regularly taking every 17 columns (because that made a book of reasonable size) and putting them out in book form. Only 9 of the early F&SF columns were omitted (of which 3 were added in prefaces to later collections), and the last 19 were never collected. That makes 22 collections (not counting several repackagings), some of which were among my earliest Asimov reading and all of which I have in paperback in a nice row on my shelf. I also have photocopies of all the uncollected columns. Some are obsolete due to later discoveries, but they all read very well.
Asimov was given free rein to write about any aspect of science that interested him. In his earlier years he had some standard topics that attracted most of his interest - astronomy, chemistry, number theory, some aspects of physics - most of which he wrote about as histories of discoveries in those fields. In later years he ranged more widely - the uncollected set includes a remarkable four-essay sequence on the technical history of photography through the invention of television. Sometimes he ventured into science policy and philosophy, or left strict science entirely, as you'll see below. His writing style also changed; in particular he became freer and more personal in his introductions.
What I thought was: how about classifying the columns by topic? I took a handy library classification scheme (not Dewey or LC) and classified each column by its main topic. Sometimes this could be arbitrary, as many of the columns are interdisciplinary. For instance, when Asimov writes about spectroscopic analysis of starlight to determine chemical composition of stars, which he did more than once, is that physics, astronomy, or chemistry? I judged by the main thrust of the article. That did mean that some sets of articles which Asimov intended as a sequence are broken apart. There are also some peculiarities due to the structure of the classification system, as we'll see. Here's the results:
All 3 of these are polemics arguing for rationality in reasoning, though each takes a different perspective. He also made this point in the specific context of science, which I class separately, but these are about thought in general.
Most of these (13) are on some aspect of number theory, at which Asimov considered himself an enthusiastic amateur. There are 3 on geometry (Euclidean, non-Euclidean, and fractal), and 2 on mensuration.
Science (general) (16)
I put here essays on the principles and philosophy of science (10) or scientific impostures or honest errors (6). The former group include lists of great scientists and defenses of scientific methodology as well as the arguments for scientific rationality which also appear in the latter group.
Includes relativity (3), gravity and ballistics (7), pressure (3), thermodynamics (8), light and the speed of light (10), sound (2), electricity & magnetism & electromagnetic radiation (11), subatomic particles (9), quantum theory (3), and electronics (5), plus a few miscellaneous items (including thalassogens, the creation of the A-bomb, and electric lighting and television as technological achievements).
Asimov's scientific training and career were in chemistry, but mostly in organic and biochemistry. Biochemistry I classify with biology, but most of his essays in straight chemistry were on physical chemistry. We have many on the periodic table and the classification of elements (10), the discovery and nature of individual elements (13), and radioactivity (5). There are also scattered essays on catalysis, valency, electrochemistry (2), spectrum analysis, silicon compounds (3), organic molecular structure, stereoisomerism, enzymes, and fuel in the sense of chemical technology (2).
Asimov's favorite science, though he never studied it. Mostly on cosmology and astrophysics (29), the sun (4), the Earth as a planet (5), the Moon (6), other individual planets and satellites (26), asteroids (5), comets and meteors (5), the solar system in general (12), types of stars (19), and the Milky Way and other galaxies (9). There are also a few on observational astronomy (5) and astrology (he's against it).
The makeup of the Earth and topics in historical geology (Cambrian fossils, radioactive dating).
Physical geography (18)
On the general topic, 5 (mountains, rivers, islands, oceans, icebergs). Also mathematical geography (5), the history of exploration (3), meteorology (3), climatology (2, both on ice ages, though in one [Jan. 1959, how's that for perspicacious?] he predicts that the greenhouse effect will mean the end of ice ages).
A lot on biochemistry, obviously, with a wide spread of subtopics (12). Also: nature of life (2), cytology (2), physiology (2), genetics and evolution (4), paleontology (2), microbiology (3).
It's on photosynthesis, which the classification puts here rather than in biochemistry.
Blood (2), thyroids, dinosaurs and their extinction (2), the platypus, and 3 on the physiology of body size (square-cube law and all).
One on evolution that's specifically about human evolution, and a social essay mostly applying physiological differences between the sexes to an argument in favor of women's rights.
Arguing that IQ tests don't measure intelligence in any meaningful way, and specifically dismissing any significance to racial test differences.
A personal essay, recounting Asimov's frustrating and aborted career in academia.
Science fiction as futurology.
Human geography (2)
Statistical essays on the population of cities.
Auxiliary sciences of history (13)
Mostly on calendars and time zones (9), with 2 on place nomenclature (but not earthly: lunar features and planets) and 2 to impress on the reader how long the Earth and the universe have existed by mapping their histories onto an imagined single year.
In later years, Asimov sometimes wished he'd chosen a career as a historian rather than a chemist. Most of these are thoughtful and imaginative accounts of the impact of the development of technology on history, including one on the impact of the longbow and one on how the geography of the Nile affected Egyptian civilization.
Two are really on science - a rebuttal of scientific-based arguments for the existence of God, and an analysis of what the star of Bethlehem might astronomically have been - and the third sociological (a brilliant interpretation of Ruth as an anti-racist polemic), but the fundamental topic is religious so I put them here.
Social welfare (4)
A few editorial-style polemics on the problems of violence, curbing personal vices (he doesn't think "Just say no" is much of an answer), and a clumsy but well-meaning one on why old women were perceived as witches, plus an outlier in the form of a personal reminiscence of a cruise to watch the launching of the last Apollo mission.
Political science (2)
More editorials, in favor of computerization to ease the functioning of society, and on world government.
Social economics (7)
Includes 6 on what Asimov considers our most urgent social problem, population growth, and 1 on energy policy.
Economic exchange (1)
Evolutionary essay on the development of tools, followed by economic media of exchange, and on into business.
Engineering and technology (13)
Runs from land transport to lighter-than-air flight to space vehicles and space flight (5, one debunking UFOs), plus robotics, the technology of fusion, tools to measure time, and photographic and motion picture cameras (3).
Etymological studies of scientific words, one on number names and one on chemical nomenclature, the famous "You, Too Can Speak Gaelic."
On science in the works of great authors (2: Shakespeare, Milton), analysis of his own background and character as a writer (2), the historical background to tub-thumping poetry (2), and the future of books (1).