zodiac revised

NASA is science and astrology is not. But that doesn’t mean that very logical, well-informed people don’t look at their horoscope once and awhile. And everyone knows what their zodiac (“circle of animals”) sign is supposed to be.

A few months ago, NASA put out some zodiac information that the popular press picked up on and took further than NASA intended.

On the science side of things, NASA made the point that the sky and positions of the stars and constellation is significantly different from the sky that the ancients used when they came up with the zodiac signs that we all have known.

The zodiac signs were created based on the calendar year of the Babylonians who  lived over 3,000 years ago. They divided the zodiac into 12 equal parts pie slices, even though they seem to have known that there were actually 13 constellations in the zodiac.  Twelve just worked neater.

The Earth orbits the Sun, so the Sun appears to pass through each of those 12 zodiac signs. That worked out nicely with their 12-month lunar calendar.

Orion stars

You can see Orion’s familiar 3-star belt. Can you see in this group of stars what the ancient Greeks thought looked like a giant hunter with a sword attached to his belt.?

What is the zodiac anyway? NASA explains it like this:

Imagine a straight line drawn from Earth though the sun and out into space way beyond our solar system where the stars are. Then, picture Earth following its orbit around the sun. This imaginary line would rotate, pointing to different stars throughout one complete trip around the sun – or, one year. All the stars that lie close to the imaginary flat disk swept out by this imaginary line are said to be in the zodiac.

One thing that NASA announced was that the thirteenth sign – which had been there all along – was Ophiuchus. NASA didn’t come with that Latin name either (meaning “serpent bearer”) it had been written about by Greek astronomer Ptolemy in the second century.

I first heard about this “news” because I follow NASA’s Tumblr account. where they said “We didn’t change any zodiac signs, we just did the math.”

In those 3000 years, the Earth, which wobbles a bit as it orbits, has shifted our view of the sky. The Earth’s axis (North pole) isn’t pointing in the same direction it was to the Babylonian viewer.

But the news that there was a thirteenth zodiac sign (Ophiuchus) and the shifting sky meant that more than 80% of us were born under a different sign. That would be true if someone redrew the sky charts and used those revised charts to do your horoscope based on when you were born. The sign you always thought was your sign actually was your sign – three millennia ago.

I had a friend in college who was really into astrology. She did a chart for me and made the point that those horoscopes that you see in magazines and online are so general for a sign that they mean almost nothing. You need a chart done for you based on the day and time you were born. I learned that astrologers use “artificial” constellations that are fixed in the Sun’s path as seen from Earth and use that to track planetary movements. Therefore, the zodiac sign dates remain the same for astrologers no matter what NASA says..

Of course, NASA doesn’t really care about your horoscope. I think their interest in all this is pretty close to my own interest in astrology. It makes you pay more attention to celestial observations.

But, if you have looked at your horoscope and found it not to be so accurate, maybe you want to consider the more modern view of the sky that was up there when you were born.  I moved from being a Libra to being a Virgo. If you were born today you are born under Ophiuchus. Some Capricorns are now finding out they are a Sagittarius. It’s like a commercial for DNA ancestry testing that I see on television – you thought you were a Cancer and now you’re a Gemini. Poor Scorpio went from being about a month to just six days long.

I checked my Libra horoscope while I was writing this. Bummer: “You probably aren’t going to feel very friendly. You’re most likely to want to sequester yourself at home and not see or speak to anyone.”  I checked in on Virgo – not much better: “Today you might get the feeling that someone in your family is hiding something. The atmosphere might be strained and somewhat tense.” Why can’t I have this one? “Venus, your personal planet, enters a dynamic and positive sector of your chart, making this the perfect time to make over your life, attitude and relationships.”

Here are NASA’s revised 13 signs and dates:

Capricorn: Jan. 20 – Feb. 16
Aquarius: Feb. 16 – March 11
Pisces: March 11 – April 18
Aries: April 18 – May 13
Taurus: May 13 – June 21
Gemini: June 21 – July 20
Cancer: July 20 – Aug. 10
Leo: Aug. 10 – Sept. 16
Virgo: Sept. 16 – Oct. 30
Libra: Oct. 30 – Nov. 23
Scorpio: Nov. 23 – Nov. 29
Ophiuchus: Nov. 29 – Dec. 17
Sagittarius: Dec. 17 – Jan. 20


Mosaic pavement from a 6th century synagogue at Beth Alpha, Israel showing the zodiac surround the central chariot of the Sun (a Greek idea) and the corners depict the 4 “turning points”  of the year, solstices and equinoxes.