I just read a short article on how your zodiac sign may have changed because scientists at a planetarium in Minnesota have "recalculate[d] the dates that correspond to each sign to accommodate millennia of subtle shifts in the Earth's axis." What they are referring to here is the Precession of the Equinoxes. Let me explain.
Where does the Zodiac Begin?
Since the beginning of horoscopic astrology in the Middle East, the beginning of the zodiac was considered 0 degrees Aries. There are two definitions of "0 degrees Aries." One is that it pinpoints the Alpha star (first brightest) in the constellation of Aries. The other is that it assigns 0 Aries to wherever the Sun is on the day of the northern Spring Equinox; this also means that the Sun enters Cancer at the Summer Solstice, Libra at the Fall Equinox, and Capricorn at the Winter Solstice. When astrology was developed about 2,000 years ago, these two points coincided. That is, at the northern Spring Equinox, the Sun happened to be right about at the Alpha star in the constellation of Aries. However, the Sun moves against the background of the stars at the rate of about 1 degree every 72 years, and it does so backwards against what we consider the normal order of the zodiac constellations. So a few hundred years after astrology was developed, the Sun would have been in the late degrees of Pisces on the day of the Spring Equinox. And it will continue to appear in that sign at the Equinox for a couple thousand years. This is what we call our current age the Age of Pisces. At some point in the next few hundred years, the Sun will be against the background of the constellation of Aquarius at the Spring Equinox, which will begin the Age of Aquarius (no, it has not yet begun, sorry to all you Age of Aquarius enthusiasts out there).
This linking of the zodiac to our seasons on Earth has become known as Tropical astrology, or using the Tropical Zodiac. As the Earth goes around the Sun each year at its 23.5 degree angle, the Sun appears to move between the Tropic of Cancer at the northern Summer Solstice, south to the Tropic of Capricorn at the northern Winter Solstice. At the Equinoxes, the Sun appears to be right over the Equator. ("Tropical" comes from the Greek and refers to the "turning" as in the turning of the Sun at the Solstices. Oxford English Dictionary Online)
The linking of the zodiac to the star at Alpha Aries has become known as the Sidereal Zodiac (siderum = star, Latin) and has continued to be used pretty much only in India among Hindu (Vedic) astrologers. Some in the West also now practice Hindu astrology for a variety of reasons, usually stemming from a false idea that Hindu astrology includes predictive and spiritual elements not found in the West. While it is true that these elements are not found in modern Western astrology, it is not true at all that they are not still there; one need dig only a bit below the modern superficial/psychological use of astrology to find them.
So the Tropical and the Sidereal Zodiacs have existed side-by-side for nearly 2,000 years. One thing is very important to note here: both zodiacs use a stylized system of 30 degrees per sign. That is, the Tropical zodiac starts 0 Aries on the Spring Equinox, and just counts 30 degrees per sign going forward from there. The Sideral zodiac starts 0 Aries whenever the Sun aligns with that star every year and also just counts 30 degrees per sign from there. In other words, the Sidereal zodiac makes no attempt to align ALL of the signs of the zodiac with ALL of the constellations that were used to originally form it. There are Sidereal astrologers out there today who claim that Sidereal astrology is "truer" or "more scientific" than Tropical astrology because it aligns with the stars or constellations; but clearly they don't recognize, or won't admit, that the Sidereal zodiac aligns only with ONE star. The constellations aren't all 30 degrees of neat packaging, so the Sidereal zodiac is just as stylized (and no more "scientific" or "true") than the Tropical zodiac.
Now this article lists the dates of the zodiac "as the ancient Babylonians intended it." The hubris of modern science! Their own list includes the now-famous (and totally modern invention) of the "13th sign" Ophiuchus, with an asterisk noting that it was "Discarded by the Babylonians because they wanted 12 signs per year." (See my blog post on this.) So on the one hand, they admit right here that they are changing what the Babylonians actually DID, while claiming that they know what the Babylonians "intended." They claim to be "restoring" the "original Babylonian zodiac." Sounds like modern scientist messing around with something that they completely and willfully misunderstand.
If you notice the list of dates on these "signs", you will see that they are not approximately 30 days each. This is because these scientists are not using the Tropical OR the Sidereal zodiac here. They are using a modern invention called the "Constellational Zodiac." See Chris Warnock's excellent page on the three zodiacs for more detail. For now, let me point out that the Constellational zodiac attempts to take all of the constellations that go into making up the zodiacal signs, inserts Ophiuchus, and then sort of stretches the length of each of these "signs" proportionally to fit the size that each constellation occupies in the sky. There are a few major problems with that. The first is that many of these constellations overlap; this is one of the things that has led to confusion about when the Age of Pisces will end and the Age of Aquarius will begin. In a hundred years or so, on the day of the northern Spring Equinox, the Sun will actually be standing in the overlap of these two signs, so there will be a cross over period for many decades before the Sun stands solely in the constellation of Aquarius at the equinox. This is because Aquarius, while standing next to Pisces, also dips in below it for a few degrees (or one could say that Pisces swims above Aquarius). The other problem with this is that with all of the signs being different sizes, it is impossible to DO anything with them. The whole point of astrology is that it represents Plato's Ideal or perfection. One way of looking at it is measuring the difference between where we really are and where our perfected self is. It is in this space that we learn about ourselves, our world, our spirituality, etc.; and it is in this space that astrology does what it was intended to do - narrate the past, present and future (predict). This is impossible to do with an odd-shaped, ill-formed, lop-sided zodiac.
1. Scientists should stay the hell out of astrology. And if you want to know what I REALLY think: scientists should stay the hell out of astrology!
Many modern astrologers have misunderstood traditional astrology because either they did not have the resources to investigate it (which was true for a while in general), or simply because they did not care to (which is often the case now). How much LESS will modern scientists understand classical astrology (e.g. what the Babylonians "intended") than modern astrologers? All they can do is complicate matters.
2. Why would astrologers even CARE what modern science has to say about astrology? Modern science is almost universally hostile to astrology; and modern scientists who do have some sympathy for our Art usually are trying to "help" by proving astrology on scientific grounds. Being a Spiritual Science, if you will, astrology will never be proven correct, true, or valid to the satisfaction of the modern academy, which is still held captive by the materialist/atheist world view. I'm not suggesting that astrologers ignore everything that modern scientists say about astrology (or any other field), but why would we give it such weight? Is their goal to work with us? In most cases, their goal is to debunk astrology completely. Do you think that these scientists who "corrected" the zodiac dates actually consulted with an astrologer? Of course not! If they had, they might have realized how absolutely ridiculous their "corrections" are.