The Difference Between Astronomy and Astrology



I'm not going to assert that belief in astrology is right or wrong. Everyone has their own truth and their own reality. It's important to respect that. What I would like to explain is the difference between astronomy and astrology and why astronomers have such a difficult time with astrology.

A little History: Astronomy and astrology were the same thing before the modern era, because predictive and divinatory knowledge was one of the motivating factors for astronomical observation. Astronomy is simply the observation and measurement of celestial bodies, while astrology is an attempt to find some sort of "meaning" or "influence" in the planetary positions. The interesting thing is that astrology gave birth to astronomy. Oddly enough, considering that astrology has to do with planetary movements, astrologers no longer look at the sky, and haven't for hundreds of years.

Modern astronomers find it difficult to connect with astrology because the data used by astrologers bears no relation to what is actually seen in the sky. Astrologers have ignored the slow "wobble" of the earth on it's axis, called the precession of the equinoxes, even though Hipparchus discovered it as long ago as 100 BC. It means that the position of the ecliptic in the sky has shifted quite a bit in the last two thousand years, so that the zodiac is not the same as it was in the year 0.

As an example, I'm always told that I'm a Cancer, since I was born in July, because the sun is in Cancer in July. Well, the sun was in Cancer 2000 years ago, but in the year I was born the sun was in Gemini, not Cancer. Anyone with a simple astronomy or planetarium program on their computer can input the year and day they were born and see for themselves what "sign" they were born under. I use Starry Night.

By the way, the plane of the earth's ecliptic now crosses the constellation Ophiuchus (it didn't 2000 years ago) so there are currently 13 zodiacal constellations in the northern hemisphere, not 12. Go to a bookstore and look at any star chart that shows the ecliptic and you will see it soaring happily through Ophiuchus! Some astrologers have suggested that the borders of the constellations are too wide. If we narrow the borders, then the constellation that gets excluded is Scorpius, not Ophiuchus. Here's a chart showing how many days the sun spends in each constellation:


Constellation:        Dates:      No of days:
Sagittarius Dec 18 Jan 18 32 Capricornus Jan 19 Feb 15 28 Aquarius Feb 16 Mar 11 24 Pisces Mar 12 Apr 18 38 Aries Apr 19 May 13 25 Taurus May 14 Jun 19 37 Gemini Jun 20 Jul 20 31 Cancer Jul 21 Aug 9 20 Leo Aug 10 Sep 15 37 Virgo Sep 16 Oct 30 45 Libra Oct 31 Nov 22 23 Scorpius Nov 23 Nov 29 7 Ophiuchus Nov 30 Dec 17 18

Even the Ancient Mayans had a Zodiac with 13 Constellations, as did the Babylonians.


          The ancient Mayan zodiac was composed of 13 constellations, including the constellation Ophiuchus, which is exactly what is seen in the sky today. The description of the 13 constellations of the Mayan zodiac is found in The Paris Codex, (Codex Peresianus), one of the very few texts of the pre-Conquest Maya that survived the book burnings by the Spanish clergy during the 16th century. As everyone by now knows, the Mayans were famous for their precise astronomical observations and their accurate predictions of eclipses and of Venus rising.

The ancient Babylonians originally started out with 13 constellations that the sun appeared to pass through. But in order to make their zodiac fit within their 12-month calendar, one of the constellations had to be left out. So Ophiuchus got the ax.

The signs of the zodic were more or less aligned with their corresponding constellations about 2,000 years ago. But in the intervening centuries, the slow wobble of the Earthís axis has caused the solstice and equinox points to shift roughly 30 degrees westward relative to the constellations! At present, the signs and constellations are about one calendar month off. In another two thousand years or so, theyíll be about two months off. Astrologers pay no attention to what is actually seen in the sky. Their predictions are based on ancient shamanic lore and have more to do with the idea of a collective consciousness, history and story-telling than physical reality.

Also, astrologers consider retrograde motion to be an important influence on their lives. In astrology, this backward movement was traditionally thought to be unlucky or inauspicious, as it went against the 'natural' order of movement. The problem is, retrograde motion is purely an optical illusion, caused by the line of sight when looking at an outer planet that is being overtaken by a faster-moving, inner planet. (There are many animated, graphic demonstrations of this on the internet). Astronomers (and many other people) have trouble believing that any part of their lives can be influenced by an optical illusion.

Retrograde Motion Made Simple

Have you ever been in a fast train that overtook another train on the next track, traveling in the same direction as your train? Through the window, the slower train looks like itís moving backwards, even though itís traveling in the same direction. This is exactly what happens when the earth catches up to another planet in a more distant orbit. As the earth passes the other planet at a higher speed, the other planet appears to be moving backwards. Like the train, it is not moving backwards. Itís purely an optical illusion. Since the time of Copernicus, astronomers have called this ďretrograde motion,Ē understanding that itís an illusion. Naturally, itís difficult for astronomers to believe that an optical illusion can have an effect on you in any way.

Here's what I have found to be both enriching and empowering in astronomy —

Astronomy is a science that compels me to seek beyond myself and our small world, a science of discovery that enriches my life by exercising my brain and my intellect. It empowers me to think clearly and rationally. It improves and sharpens critical thinking skills.

I believe that my destiny is in my own hands, and not in the accidental configuration of planets and stars.

It's the sheer fascination for space and the possibilities of worlds beyond our own and a science beyond our current understanding that encourages astronomers to think outside the box and develop his or her intellect to the fullest. From the time of Galileo, our lives have been enriched beyond measure by scientific discovery.

Be in charge of your life. Experience the mystery, awe, and excitement of observational astronomy. Find your local astronomy club, go to a star party, and look up!


Pseudoscience (Far too many TV documentaries)


Scientists are often quoted as saying, "Extraordinary claims require extraordinary evidence".

An extraordinary claim is one that contradicts a fact that has been well established and is widely accepted in the scientific community. "Scientific facts" are really just statements that have a very high degree of certainty. To contradict such a statement, you had better have evidence available that is even higher up the certainty scale. A "leap of faith" is not evidence. An emotional attachment to an idea is not evidence.

So why don't scientists bother to refute the claims of all the pseudoscientists running around? Easy--first, there are so many false claims out there that the legitimate scientist wouldn't have any time left to do anything else. If an extraordinary claim doesn't come from a credible source in the first place, that is, from someone who has the credentials to propose the idea, then it just doesn't make any sense to dignify it with a response. If you want to propose a theory about an ancient civilization, you better have a verifiable, reputable background in that field with at least some history of publications and recognition. That is to say, you better have put in the work. If you haven't, why should someone who has put in the years of work required to understand that field bother to respond to your claims?

Why do some people want to believe so desperately in the nonsense that they espouse? Bad science is everywhere, not only in print and on the web, but especially on television.

The most obvious reason for the proliferation of bad science is that it helps create a bigger audience, good ratings and increased advertising revenues. Similarly, no newspaper editor can be convinced that he will increase his paper's circulation by canceling the astrology column and replacing it with an astronomy column. Publishers have found that books on astrology make money for them. But beyond the obvious profit motive, why do some people actually believe the nonsense that they are peddling?

An article in the May 2003 Archaeology magazine sheds some light on the trend and the people who preach nonsense. "They tend to be anti-establishment, suspicious of authority, suspicious of science. They like to strike this populist pose of the little man fighting against the big university professors. Pseudoarchaeology fans get attracted to all sorts of odd notions. Their ancient civilizations, for instance, are better than ours, more peaceful, more spiritually attuned. Like anybody else, they are attracted to good stories, and pseudoarchaeology tells sensational stories."

Carl Sagan spoke directly to the point. Real science, he pointed out, is hard. It requires critical thinking skills that many people simply never develop, and it's much easier to believe a simplistic version of, for instance, creation, than to study the facts and discover what really happened. Pseudoscientists "long for the scientific seal of approval, but are unwilling to put up with the rigorous standards of evidence that impart credibility to that seal."

Finally, psychologists tell us that some people are so desperate for attention of any kind that they even welcome negative attention. For this reason, they take to the web and cross-post their ridiculous notions everywhere. Their posts may show up on a newsgroup that you subscribe to, even though they don't subscribe to it themselves and never read it! Responding to their posts only feeds into their desperate need for attention. The best way to respond to such people is to completely ignore them. It makes absolutely no sense to engage them in a discussion about their beliefs because their motives for believing nonsense are purely emotional, not logical. To attempt any sort of discussion at all quickly becomes hopeless.

A piece written by Michael Shermer for Scientific American, "Smart People Believe Weird Things", August 12, 2002, explains this phenomenon quite well. Here are some excerpts:

"Smart people believe weird things because they are skilled at defending beliefs they arrived at for non smart reasons."

"Students are taught what to think but not how to think."

"For those lacking a fundamental comprehension of how science works, the siren song of pseudo science becomes too alluring to resist, no matter how smart you are."

These Links are both fun to read and informative:
  • Bad Astronomy Astronomy mistakes in film and the news media.
  • CSICOP encourages the critical investigation of paranormal and fringe-science claims from a responsible, scientific point of view and disseminates factual information about the results of such inquiries to the scientific community and the public.
  • Astrology FAQ--Who cares? A critical look at astrology and who is making money with it.
  • The Scientific Method

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