Understanding Astrology:
A critical review of a thousand empirical studies 1900-2020

Abstract Fifty years ago empirical studies were the hardest things to find in astrology. Today there are more than a thousand of them hidden in a hundred journals, dozens of books, academic theses, conference reports, websites, unpublished studies, and little-known hard-to-find specialised collections. For the first time this new book collects all of them -- not just the ones selected to prove a point -- and subjects them to rigorous critical thinking. The results explain why for many people there is more to astrology than being true or false. Understanding Astrology has 952 pages, more than 650,000 words, 750 pictures, 650 graphs, nearly 500 tables, over 4000 references, glossary (85 entries), name and subject indexes, and a concise style free of waffle. It is Open Access and can be downloaded for free as four pdf files totalling nearly 40 MB, see full article below. No registration or login is required. Hardcover copies with a durable sewn binding (lies flat) are available direct from the publisher for 65 euros excluding postage. Not available in paperback or from bookshops. Important: Published in late 2022, it updates the information on the www.astrology-and-science.com website.

Wide interdisciplinary appeal
Depending on who we are, astrology can be entertaining, beautiful, therapeutic, lucrative, misleading, dangerous, or simply stupid. But always challenging, because half the population believes in it, skeptics deny it, vested interests distort it, astrologers can disagree on mostly everything, and most scientists are not interested. Something that is this popular and this confused deserves careful critical scrutiny -- except careful critical scrutiny has always been the hardest thing to find in astrology. Until now.

The evolution of Understanding Astrology
Fifty years ago calculating a birth chart was too time-consuming for most researchers into astrological claims. As a result few empirical research studies existed. Examples included John Nelson on shortwave radio quality, Vernon Clark on the performance of astrologers, John Addey on harmonics, and Michel Gauquelin on professional occupations. All were reviewed in Recent Advances in Natal Astrology: A Critical Review 1900-1976, the result of a unique international collaboration between more than 50 astrologers and scientists from 10 countries. It led to annual London research conferences and in 1981 to the re-founding of Correlation, the AA's journal of research into astrology. It also received international acclaim:

Recent Advances in Natal Astrology It had 250,000 words, nearly 110 figures, over 1000 references. "The most important book ever written on astrology" (Phenomena Publications Canada). "A must for any serious scientific student of astrology" (Astrological Magazine India). "A milestone in astrological book publishing" (FAA Journal Australia)."The most talked-about astrology book ever" (Emergence bookshop UK). "Easily readable and always informative" (Cosmecology Bulletin USA). "What a book! It will go into history as one of the most important books of western astrology" (Tijdschrift Astrologie The Netherlands). "A major work, indeed the only one of its kind" (Professor H J Eysenck, University of London).

This new survey evolved via earlier works published in Amsterdam by AinO Publications, long-time publisher of research journals and books for the Nederlandse Vereniging tot Wetenschappelijk Onderzoek van de Astrologie, the Dutch Society for the Scientific Study of Astrology. The Society began in 1971, ten years before the AA founded Correlation, and was perhaps the first in the world to be aimed at both serious practitioners and serious critics while maintaining high standards on both sides.

Shown above, the journals are the Dutch Journal of Astrology started in 1977, Science and Astrology 1981, Astrology under Scrutiny 1986, and the same in English 2000. The books are Astrology under Scrutiny 2013 featuring an anthology of articles since the first issue, which was expanded into Tests of Astrology 2016 to include more international work (the cover illustrates Gauquelin's famous Mars effect). Six more years of work led to the present Understanding Astrology: A critical review of a thousand empirical studies 1900-2020, published in late 2022, which in effect updates the earlier 1900-1976 coverage of Recent Advances. It also involves some of the original compilers and helpers.

At 1.8kg Understanding Astrology is seriously comprehensive
It has 952 pages 170x240 mm, and more than 650,000 words, 750 pictures, 650 graphs, nearly 500 tables, over 4000 references, glossary (85 entries), name and subject indexes, and a concise style free of waffle. The mean measured readability is well within ordinary education levels, which with an average of just over one bold heading per page makes navigation easy. Some parts are necessarily technical but there are always plain-English summaries helped by hundreds of explanatory visuals like these:

Availability
Hardcover copies with a sewn binding (lies flat) are available direct from the publisher in Amsterdam for 65 euros each (about $US60) excluding air mail postage -- the Dutch post office does not deliver by sea mail. You can pay by PayPal or ebank but not credit card. To check availability and postage costs, please email the publisher wout DOT heukelom AT hetnet DOT nl. The book has an ISBN (978908-249291-0) but to keep the price low it is not available via bookshops or as a paperback. The entire work is Open Access and can be downloaded for free as four searchable pdf files totalling 39.2 MB. Each pdf takes up to three minutes to download depending on your computer and local traffic.

Downloads To download the pdf files visit the download page. No registration or login is required. You are welcome to use the material and distribute it to others for free but please mention the source (book title, authors, publisher, book date, page numbers). The publisher welcomes your comments (email as above also in book and pdfs).

So why buy a hardcover copy?
To avoid huge file sizes the downloadable pdfs are necessarily lower in resolution than the printed version. Text is largely unaffected but fine detail in the pictures and graphs may be hard to read. You are welcome to print out a full copy rather than squint your way through a thousand pages on-screen, but you will of course need lots of paper (print size is already at the lower limit for continuous reading, which makes 2-up copies a challenge). A hardcover copy is cheaper (6c US a page), nicer to look at, lies flat, and is much easier to use, with no loose pages to clutter your reading space. As one Swiss reader told us, "I have seen your website and downloaded the four pdfs. Would like to buy a hard copy".

Praise for Understanding Astrology
"A mammoth undertaking ... will soon become the de facto standard reference" ­­ Philip Graves, historian, world's largest astrology reference collection, Wales.

"It will be the classic sourcebook for all previous astrology research" -­ Brad Kochunas, licensed counsellor, Ohio.

"The ultimate guide, truly comprehensive, one of á kind, promotes critical thinking" ­­ Catherine Sinclair, researcher, Universite de Lyon, France.

"Surely THE definitive critical review of astrology research" ­­ Professor Caroline Watt, University of Edinburgh.

"Very impressive tour de force" ­­ Proressor James Alcock, York University, Toronto.

"The definitive work on the topic, wilì be consulted for years to come" -­ Professor Richard Wiseman, University of Hertfordshire.

"Monumental accomplishment" ­­ Professor John T Burns, Bethany College, West Virginia.

"I am overwhelmed -­ invaluable to anyone interested in astrological research" ­­ Dr Peter Niehenke, former president of the German AA, now resident in Switzerland.

"I described its precursor as 'the most comprehensive summary on the subject' and this one is even more so ... absolutely excellent" ­­ Ray Ward, Skepticaì Intelligencer 2023.

"It is a wonderful book! Beautifully laid out, easy to handle, choice of paper is excellent, size of the book is perfect. And the pages lie flat without print being smashed into the center binding. At $US60 it is like giving away a book of such quality. Publishing the book in hardback was an excellent choice. I expect I will be reading it for many weeks, and sections for years. Many thanks for a miraculous publication!" -- Veteran US researcher Therese Hamilton (see below in blue for her views on Tests of Astrology).

"A milestone in bringing together in one place reported studies and related writings on astrological claims that were previously impossibly scattered. The result is a critical synthesis of information well beyond the confines of astrology. For believers, skeptics, historians, academics, and researchers generally, this is a challenging, invaluable and unique resource." -- Donald H Saklofske, professor of psychology at the University of Western Ontario, past editor of Personality and Individual Differences, past president of the International Society for the Study of Individual Differences.

A dissenting overview by Robert Currey, editor of the Astrological Association's research journal Correlation and proprietor of Equinox chart calculation and interpretation services, condensed from its original 7800 words in Correlation 35(2), 63-83, 2023.

"It is more about scientism than science. It is fatally marred by a disturbing number of misquotes, omissions, fallacious arguments, lack of controls, straw man tests, unscientific or anecdotal tests, flawed tests, irrelevant tests, an unacceptable level of methodological diversity, and a contrived and implausible line of reasoning that crumbles upon closer examination. There is also a love of fantasy -- its claimed thousand viable empirical studies do not exist."

Praise for its 2016 precursor Tests of Astrology
Unsolicited comments from nine readers:
"Very impressive ... Prodigious effort ... Should be the definitive account of astrology for the foreseeable future ... A high standard of professionalism in layout and editing ... An absolute boon to have such a huge amount of information collected in one source ... A perfect reference ... Impressive ... It is TERRIFIC, an astounding reference book ... Congrats on another magnum opus!"

From veteran US researcher Therese Hamilton
"I am greatly enjoying Tests of Astrology. The book is very attractively laid out, with an initial approach that is entertaining, humorous and factual. The background research required for the thousands of quotes and citations (articles, PhD theses, Internet links, personal communications, 600+ books) can only be called massive. Even if Tests of Astrology provides little or no support for astrology, I see this book as a 'must have' reference for serious researchers. At almost 500 pages of meticulously formatted text and graphics, TOA is actually several books bound into one volume. Congratulations on a Herculean task!"