The Universe At Your Fingertips Activity: Activities With Astrology


These activities help students to understand the difference between science and pseudoscience by investigating some of astrology's claims. Letting students have a good discussion can be very effective. We encourage you to read "Your Astrology Defense Kit" before doing these activities.

Students test the validity of astrology with three activities:

1. Charting birthdates of U.S. presidents

2. Comparing horoscopes in different newspapers

3. Attempting to identify their own horoscope from an unidentified list of daily predictions

This activity was written by Andrew Fraknoi (Foothill College and Astronomical Society of the Pacific) and incorporates suggestions by Diane Almgren, Daniel Helm and Dennis Schatz.
Copyright © 1995, Astronomical Society of the Pacific, 390 Ashton Ave., San Francisco, CA 94112. This activity may be reproduced for nonprofit purposes.

Activity Description

Activity 1: Testing Astrology with the Birthdays of the Presidents

Astrologers will tell you that the Sun sign (which is the sign of the zodiac the Sun was in when a individual was born) is a crucial factor for the occupation a person chooses and a strong determinant of overall personality as it relates to one's job. As an example of how we can test such a hypothesis, students can examine the birthdates of the 41 men who have successfully run for the job of President of the United States.

After all, it takes a certain kind of personality to be President (outgoing, well-spoken, ambitious). If personality and occupation are strongly affected by Sun sign, we should find that the birthdays of the Presidents are clustered in one (or a few) signs. If Sun signs do not affect personality and occupation, the Presidents' birthdays should be randomly distributed among the zodiac signs.

Students will fill out a worksheet to determine the astrological signs of the 41 Presidents and discuss their results. You will need to review the concept of random distribution before doing this activity.

How many Presidents do students expect to find under each sign if the birthdays of the 41 Presidents are randomly distributed among the 12 signs of the zodiac?

Since there are 41 people, chance would classify 3.4 people (41 people divided among 12 signs = 3.4 people per sign) into each of 12 random "bins." With only 41 data points, you might expect one or two fewer or one or two more Presidents in a given sign.

Extending the Activity:

Encourage students to discuss other ways to test this hypothesis. What occupations are also personality-driven but have more than 41 people in them? (As discussed in Your Astrology Defense Kit, one group of statisticians tested all the men who re-enlisted in the Marine Corps - definitely a personality related career choice!)

Activity 2: Horoscopes from Different Astrologers

In this activity, students compare horoscopes in different newspapers from the same day. Ask students to bring in newspapers or buy them yourself. You can also copy newspapers from a local library, although using photocopies reduces the psychological impact of the activity somewhat. The more newspapers you have, the better the activity.

Cut the horoscope sections out of the papers and distribute them to students. If possible, cut out the horoscopes in full view of the students for greater impact. Ask several students to read aloud the different horoscopes of one or more selected students from the various newspapers. Discuss the following questions:

1. How well do the predictions of different astrologer agree for that student's sign?

2. How specific are the newspaper statements?

3. In what ways could the statements apply to different people?

Have the students discuss some reasons why the predictions in astrology columns might be so general and vague. If there is time, continue the discussion by bringing up some of the "embarrassing questions about astrology" in Your Astrology Defense Kit.

Activity 3: Mixed-up Horoscopes

In this activity, students try to find their own sign from a variety of unidentified signs in a horoscope column. Use an astrology column from a recent newspaper (today, yesterday, or last weekend). It is best to use an out-of-town newspaper so students are not likely to have seen it. Cut out the horoscopes and remove the dates, signs and any telltale references to the sign, like "you're a real lion at times." Be sure to make a copy of the full column for yourself and put it aside. Mix up the order of the descriptions, and give each one a number from 1 to 12. Transfer these numbers to your copy for future reference.

Have each student write down his or her name and birthday on a piece of paper. Distribute the sheet with all the numbered (but otherwise unlabeled) horoscopes to the students and have them select the one description that best fits the day in question. (Be sure you remind them of the day the horoscopes apply.)

Ask the students to predict how they think this experiment will turn out. To prevent sudden changes of answers, ask students to exchange papers at this point. Then put the signs and birthdates associated with each numbered paragraph on the board. Have the class count how many students picked their own sign among the 12 and how many did not.

If Sun sign astrology predicts one's day pretty well and everyone remembers the day in question clearly (the astrologer's hypothesis), students should in general be able to find their own paragraph. But if chance instead of the stars governs the composition of those descriptions (the skeptic's hypothesis), we would expect that only one out of 12 of the students would have selected the description for their own signs.

Warning: With small numbers of students in one class, it often happens by chance that there are a few more correct picks than one would expect by chance. With older students, this can give you a chance to discuss the need for large samples in good statistical studies. If students get intrigued by such extra hits, one way to check is to extend the test to other students or school staff.


These three activities are designed to

1. Help students think critically about the pseudoscience of astrology.

2. Become familiar with the kind of statistical testing that scientists do to evaluate hypotheses.

Tips and Suggestions


Activity 1

Activity 2

Activity 3

Your Astrology Defense Kit by Andrew Fraknoi  

It happens to all of us - astronomers, amateurs, and teachers. We tell someone about our interest in the heavens and quickly get drawn into a debate about astrology. For many of us it's hard to know how to respond politely to someone who takes this ancient superstition seriously.

The revelation that daily schedules in the Reagan White House were arranged and rearranged based on the predictions of a San Francisco astrologer focused new attention on astrology's widespread public acceptance. More than ever, we are likely to face questions about astrology, especially among young people. So here is a quick guide to some of the responses you can make to astrologers' claims.

The Tenets of Astrology

The basis of astrology is disarmingly simple: a person's character and destiny can be understood from the positions of the Sun, Moon, and planets at the moment of his or her birth. Interpreting the location of these bodies using a chart called the horoscope, astrologers claim to predict and explain the course of life and to help people, companies, and nations with decisions of great import.

Implausible as such claims may sound to anyone who knows what and how distant the Sun, Moon, and planets really are, a 1984 Gallup Poll revealed that 55 percent of American teenagers believe in astrology. And every day thousands of people around the world base crucial medical, professional, and personal decisions on advice received from astrologers and astrological publications.

The details of its precise origins are lost in antiquity, but astrology is at least thousands of years old and appears in different forms in many cultures. It arose at a time when humankind's view of the world was dominated by magic and superstition, when the need to grasp the patterns of nature was often of life-and-death importance.

Celestial objects seemed in those days to be either gods, important spirits, or, at the very least, symbols or representatives of divine personages who spent their time tinkering with humans' daily lives. People eagerly searched for heavenly signs of what the gods would do next.

Seen in this context, a system that connected the bright planets and "important" constellations with meaningful life questions was appealing and reassuring. (Astrologers believe that the important constellations are the ones the Sun passes through during the course of a year; they call these the constellations of the zodiac.) And even today, despite so much effort at science education, astrology's appeal for many people has not diminished. For them, thinking of Venus as a cloud-covered desert world as hot as an oven is far less attractive than seeing it as an aid in deciding whom to marry.

Ten Embarrassing Questions

A good way to begin thinking about the astrological perspective is to take a skeptical but good-humored look at the logical consequences of some of its claims. Here are my 10 favorite questions to ask supporters of astrology:

1. What is the likelihood that one-twelfth of the world's population is having the same kind of day?

Proponents of newspaper astrology columns (which appear in more than 1,200 dailies in the United States alone) claim you can learn something about your day by reading one of 12 paragraphs in the morning paper. Simple division shows that this means 400 million people around the world will all have the same kind of day, every single day. Given the need to fill so many bills at once, it is clear why astrological predictions are couched in the vaguest and most general language possible.

2. Why is the moment of birth, rather than conception, crucial for astrology?

Astrology seems scientific to some people because the horoscope is based on an exact datum: the subject's time of birth. When astrology was set up long ago, the moment of birth was considered the magic creation point of life. But today we understand birth as the culmination of nine months of steady development inside the womb. Indeed, scientists now believe that many aspects of a child's personality are set long before birth.

I suspect the reason astrologers still adhere to the moment of birth has little to do with astrological theory. Almost every client knows when he or she was born, but it is difficult (and perhaps embarrassing) to identify a person's moment of conception. To make their predictions seem as personal as possible, astrologers stick with the more easily determined date.

3. If the mother's womb can keep out astrological influences until birth, can we do the same with a cubicle of steak?

If such powerful forces emanate from the heavens, why are they inhibited before birth by a thin shield of muscle, flesh, and skin? And if they really do and a baby's potential horoscope is unsatisfactory, could we delay the action of the astrological influences by immediately surrounding the newborn with a thin cubicle of steak until the celestial signs are more auspicious?

4. If astrologers are as good as they claim, why aren't they richer?

Some astrologers answer that they cannot predict specific events, only broad trends. Others claim to have the power to foresee large events, but not small ones. But either way astrologers could amass billions by forecasting general stock-market behavior or commodity futures, and thus not have to charge their clients high fees. In October, 1987, how many astrologers actually foresaw Black Monday when the stock market took such a large tumble and warned their clients about it?

5. Are all horoscopes done before the discovery of the three outermost planets incorrect?

Some astrologers claim that the Sun sign (the location of the Sun in the zodiac at the moment of birth), which most newspaper horoscopes use exclusively, is an inadequate guide to the effects of the cosmos. These serious practitioners (generally those who have missed out on the lucrative business of syndicated columns) insist that the influence of all major bodies in the solar system must be taken into account - including the outmost planets Uranus, Neptune, and Pluto, which were not discovered until 1781, 1846, and 1930, respectively.

If that's the case, what happens to the claim many astrologers make that their art has led to accurate predictions for many centuries? Weren't all horoscopes cast before 1930 wrong? And why didn't the inaccuracies in early horoscopes lead astrologers to deduce the presence of Uranus, Neptune, and Pluto long before astronomers discovered them?

6. Shouldn't we condemn astrology as a form of bigotry?

In a civilized society we deplore all systems that judge individuals by sex, skin color, religion, national origin, or other accidents of birth. Yet astrologers boast that they can evaluate people based on another accident of birth - the positions of celestial objects. Isn't refusing to date a Leo or hire a Virgo as bad as refusing to date a Catholic or hire a black person?

7. Why do different schools of astrology disagree so strongly with each other?

Astrologers seem to disagree on the most fundamental issues of their craft: whether to account for the precession of the Earth's axis (see the box below), how many planets and other celestial objects should be included, and - most importantly - which personality traits go with which cosmic phenomena. Read ten different astrology columns, or have a reading done by ten different astrologers, and you will probably get ten different interpretations.

If astrology is a science, as its proponents claim, why are its practitioners not converging on a consensus theory after thousands of years of gathering data and refining its interpretation? Scientific ideas generally converge over time as they are tested against laboratory or other evidence. In contrast, systems based on superstition or personal belief tend to diverge as their practitioners carve out separate niches while jockeying for power, income, or prestige.

8. If the astrological influence is carried by a known force, why do the planets dominate?

If the effects of astrology can be attributed to gravity, tidal forces, or magnetism (each is invoked by a different astrological school), even a beginning physics student can make the calculations necessary to see what really affects a newborn baby. These are worked out for many different cases in Roger Culver and Philip Ianna's book Astrology: True or False (1988, Prometheus Books). For example, the obstetrician who delivers the child turns out to have about six times the gravitational pull of Mars and about two thousand billion times its tidal force. The doctor may have a lot less mass than the red planet, but he or she is a lot closer to the baby!

9. If astrological influence is carried by an unknown force, why is it independent of distance?

All the long-range forces we know in the universe get weaker as objects get farther apart. But, as you might expect in an Earth-centered system made thousands of years ago, astrological influences do not depend on distance at all. The importance of Mars in your horoscope is identical whether the planet is on the same side of the Sun as the Earth or seven times farther away on the other side. A force not dependent on distance would be a revolutionary discovery for science, changing many of our fundamental notions.

10. If astrological influences don't depend on distance, why is there no astrology of stars, galaxies, and quasars?

French astronomer Jean-Claude Pecker has pointed out that it seems very small-minded of astrologers to limit their craft to our solar system. Billions of stupendous bodies all over the universe should add their influence to that of our tiny little Sun, Moon, and planets. Has a client whose horoscope omits the effects of Rigel, the Crab pulsar, and the Andromeda Galaxy really had a complete reading?

Testing Astrology

Even if we give astrologers the benefit of the doubt on all these questions - accepting that astrological influences may exist outside our current understanding of the universe - there is a devastating final point. Put simply, Astrology doesn't work. Many careful tests have now shown that, despite their claims, astrologers really can't predict anything.

After all, we don't need to know how something works to see whether it works. During the last two decades, while astrologers have somehow always been a little too busy to conduct statistically valid tests of their work, physical and social scientists have done it for them. Let's consider a few representative studies.

Psychologist Bernard Silverman of Michigan State University looked at the birth dates of 2,978 couples who were getting married and 478 who were getting divorced in the state of Michigan. Most astrologers claim they can at least predict which astrological signs will be compatible or incompatible when it comes to personal relationships. Silverman compared such predictions to the actual records and found no correlations. For example "incompatibly signed" men and women got married as frequently as "compatibly signed" ones.

Many astrologers insist that a person's Sun sign is strongly correlated with his or her choice of profession. Indeed, job counseling is an important function of modern astrology. Physicist John McGervey at Case Western Reserve University looked at biographies and birth dates of some 6,000 politicians and 17,000 scientists to see if members of these professions would cluster among certain signs, as astrologers predict. He found the signs of both groups to be distributed completely at random.=09

To overcome the objections of astrologers who feel that the Sun sign alone is not enough for a reading, physicist Shawn Carlson of the Lawrence Berkeley Laboratory carried out an ingenious experiment. Groups of volunteers were asked to provide information necessary for casting a full horoscope and to fill out the California Personality Inventory, a standard psychologists' questionnaire that uses just the sorts of broad, general, descriptive terms astrologers use.

A "respected" astrological organization constructed horoscopes for the volunteers, and 28 professional astrologers who had approved the procedure in advance were each sent one horoscope and three personality profiles, one of which belonged to the subject of the horoscope. Their task was to interpret the horoscope and select which of the three profiles it matched.

Although the astrologers had predicted that they would score better than 50 percent correct, their actual score in 116 trials was only 34 percent correct - just what you would expect by guessing! Carlson published his results in the December 5, 1985, issue of Nature, much to the embarrassment of the astrological community.

Other tests show that it hardly matters what a horoscope says, as long as the subject feels the interpretations were done for him or her personally. A few years ago French statistician Michel Gauquelin sent the horoscope for one of the worst mass murderers in French history to 150 people and asked how well it fit them. Ninety-four percent of the subjects said they recognized themselves in the description.

Geoffrey Dean, an Australian researcher who has conducted extensive tests of astrology, reversed the astrological readings of 22 subjects, substituting phrases that were the opposite of what the horoscopes actually stated. Yet the subjects in this study said the readings applied to them just as often (95 percent of the time) as people to whom the correct phrases were given. Apparently, those who seek out astrologers just want guidance, any guidance.

Some time ago astronomers Culver and Ianna tracked the published predictions of well-known astrologers and astrological organizations for five years. Out of more than 3,000 specific predictions (including many about politicians, film stars, and other famous people), only about 10 percent came to pass. Veteran reporters - and probably many people who read or watch the news - could do a good deal better by educated guessing.

If the stars lead astrologers to incorrect predictions 9 times out of 10, they hardly seem like reliable guides for decisions of life and affairs of state. Yet millions of people, including the former First Lady, seem to swear by them.

Clearly, those of us who love astronomy cannot just hope that the public's infatuation with astrology will go away. We must speak out whenever it is useful or appropriate - to discuss the shortcomings of astrology and the shaky ground it is based on. Those of us working with youngsters can use these ideas to develop a healthy skepticism in the students and encourage an interest in the real cosmos - the one of remote worlds and suns that are mercifully unconcerned with the lives and desires of the creatures on planet Earth. Let's not allow another generation of young people to grow up tied to an ancient fantasy, left over from a time when we huddled by the firelight, afraid of the night.