Dec 21 2015

A Muddled Defense of Astrology

astrologyYeah, I know. Astrology. That is seriously old school. What is amazing is that there are still people who vehemently defend this ancient superstition. It is a window into the flaws and biases of the human brain.

In a way the exact topic of this discussion does not matter. By studying any scientific discipline in detail one can learn many generalizable lessons about science itself, and even knowledge itself. Similarly, by studying any one pseudoscience one can learn many generic lessons about the nature of pseudoscience – although, it is easier to see these lessons when one studies at least several pseudosciences and sees the commonality among them.

Having written hundreds of articles about different pseudosciences, I often feel I could just click in specific names to general arguments. The details, however, do matter as they provide specific examples that aid in understanding the underlying principles and how to apply them. We tend to compartmentalize knowledge, and so seeing many different examples really does drive the concept home and help apply it broadly – especially to our own thinking. 

Empirical Astrology

The topic today is a website that promises to offer “empirical astrology” and to make it “no longer acceptable to say astrology is rubbish on a scientific basis.” The author, Robert Currey, chose to begin his treatise with a string of straw men, rather than getting quickly to the empirical evidence. In fact, he could have skipped the straw men entirely – it only weakened his overall case.

He begins by laying out his basic case:

Though we don’t know how it works physically, astrology is not a faith. You can experience, observe and know how it applies first hand. There are sound reasons why it has proved so difficult to test the real practice of astrology under scientific conditions and why so many tests have been flawed. However, some simple experiments have yielded results that are consistent with a scientific basis to the fundamental premise of astrology even though the practice is an art rather than a science.

His first point, one that is common to many pseudosciences, is that the lack of understanding of a mechanism does not mean astrology does not work. While technically true, this has to be put into proper perspective.

First, not knowing the mechanism is not the same thing as there being no possible mechanism within known science. This goes to plausibility. He uses as his examples the loadstone and germ theory. These are bad analogies – he is comparing the transition from prescience to a scientific understanding of the world with our modern scientific understanding replacing an old superstition.

There is no possible way the apparent position of the planets with respect to each other and the stars at the moment of birth could influence the functioning of the brain. It’s not just unlikely – it is as close to impossible as we get in science. It is so unlikely, it would require a fundamental misunderstanding of how the universe works. The bar for evidence is therefore very high.

Currey, proposes several possible mechanisms, which just reinforce how impossible astrology is. He proposes “gravitational resonance,” which seems like a fancy term for tidal forces. He then appeals to our current ignorance of how gravity works. The problem with any gravitational hypothesis is that the gravitational effects of any celestial body other than the earth on any person is insignificant.

Tidal forces, because they depend upon the difference in distance from one side of an object to another, are even tinier, and do not rescue gravitation as a possible mechanism. The tidal forces even of the moon (let alone any of the planets) across your skull is insignificant. Further, Currey makes no mention of how these forces would imprint on the brain at the time of birth.

He then adds a theory that these tidal forces affect the magnetosphere of the earth. The sun and moon maybe, not the planets, and again – so what? The magnetosphere of the earth does not affect our brain development or function. It barely makes a compass needle move.

He then writes:

Many astrologers believe that the observed (terrestrial/extra-terrestrial) correlation reflects an acausal connecting principle or ‘synchronicity’ as proposed by Swiss psychiatrist and founder of analytical psychology, Dr Carl Gustav Jung.

There is a reason why Jung’s ideas have not had an impact on science in the last century. If you are appealing to an “acausal” mechanism, you are just waving your hands and saying it’s magic. This notion does not alter the implausibility of astrology one bit.

That is all he has for mechanism, except an ending flourish in which he appeals to our current ignorance of quantum mechanics (you knew that was coming).

In other words – no plausible mechanism. It is reasonable, therefore, to treat astrology as impossible unless there were undeniable empirical evidence for a real phenomenon.

I will add another layer of implausibility. If astrology were true, that would mean that ancient pre-scientific cultures came up with an elaborate system based on their primitive superstitions that turned out to be true (and not only in some vague general sense, but in detail). They would have had to do this prior to accurate calendars and clocks being available. This is so unlikely by coincidence, if it were true it would demand yet another explanation that challenges our understanding of reality.

Skipping past all of his silly straw men in which he attacks off the cuff comments by random people calling themselves skeptics, he finally gets to the empirical evidence. You can probably see what’s coming, the same exact pattern we see with proponents of other highly implausible claims – cherry picking.

Just like with ESP, astrologers have failed to provide evidence for a real phenomenon that will convince a properly skeptical scientists. This would require evidence that is simultaneously (that’s the part they always miss) statistically significant, with rigorous study design, a reasonable effect size, and reliably replicated.

The examples Currey provides do not meet these reasonable criteria. I will focus on perhaps the most famous – Michel Gauquelin’s “Mars Effect,” in which he claims that accomplished athletes (and other accomplished individuals) are born more often under Mars in sector 1 and 4.

As a reminder, it is extremely easy to manipulate data, so much so that many researchers do it inadvertently.  One of the common ways to do this is to data mine, to look through large sets of data for statistical anomalies. A related way is to do multiple comparisons, but then only include the comparisons that produce positive results.

These behavior distort the statistics, because they pretend that random data was analyzed only for one comparison determined ahead of time. Multiple comparisons is similar to claiming that you can always flip heads on a fair coin, then flipping the coin as many times as you have to until you get heads, then declaring success.

The accusation that Gauquelin’s data is the result of multiple comparisons (and therefore not legitimate) has never been refuted. It remains a legitimate criticism. Currey presents many standard arguments, including that CSICOP replicated the Mars Effect. They didn’t – they analyzed a subset of the data and found the same effect. But that is not a replication, the data is already tainted by post-hoc cherry picking. Only a fresh set of data would replicate the effect.

He gives other examples, but the story is always the same. Astrologers have the huge burden of proof to show that there is a real effect, that replicates under independent rigorous conditions. They have failed to do so. Their data is always flawed, or does not replicate.


Astrology remains implausible in the extreme, the functional equivalent of magic. The evidence offered to support astrology is flawed and weak. The excuses offered to explain the flawed and weak evidence are invalid and unconvincing.

The simplest and most likely explanation remains that astrology is a pre-scientific superstition with no basis in reality. It reflects only the stubborn flaws in human thinking.

It does serve as a persistent window into those flaws, and therefore can serve as an occasional example of them.

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