In Western astrology, astrological signs are the twelve 30° sectors of the ecliptic. The order of the astrological signs is Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius and Pisces. Each sector is named for a constellation it passes through.
The concept of the zodiac originated in Babylonian astrology, and was later influenced by Hellenistic culture. According to astrology, celestial phenomena relate to human activity on the principle of "as above, so below", so that the signs are held to represent characteristic modes of expression.
This is the truth, the whole truth and nothing but the truth:
As below, so above; and as above so below. With this knowledge alone you may work miracles.
And since all things exist in and emanate from the One Who is the ultimate Cause, so all things are born after their kind from this One.
The Sun is the father, the Moon the mother;
the wind carried it in his belly. Earth is its nurse and its guardian.
It is the Father of all things,
the eternal Will is contained in it.
Here, on earth, its strength, its power remain one and undivided.
Earth must be separated from fire, the subtle from the dense, gently with unremitting care.
It arises from the earth and descends from heaven; it gathers to itself the strength of things above and things below.
By means of this one thing all the glory of the world shall be yours and all obscurity flee from you.
It is power, strong with the strength of all power, for it will penetrate all mysteries and dispel all ignorance.
By it the world was created.
From it are born manifold wonders, the means to achieving which are here given
It is for this reason that I am called Hermes Trismegistus; for I possess the three essentials of the philosophy of the universe.
This is the sum total of the work of the Sun.
Sadoul, Jacques. Alchemists and Gold. Spearman, 1972. Fulcanelli interpretation of The Emerald Tablet, p. 25,26:
The Zodiac & The Superposition Principle
What, beyond the poetry does this have to do with astrology? The Three Essentials Hermes Trismegistus was referring to are alchemy, theurgy, and astrology, though you'll note, this "power" he's referring to there doesn't exist as a one way path, nor does it "originate" in any one place between the cosmos and down here on earth: it is in fact, above, below, within and without. As opposed to an abdication of personal power to some far flung deity or planet, this is an avid endorsement of owning it.
The zodiac, by definition is not just your Sun sign. In fact, it is simply defined as being: "a belt of the heavens within about 8° either side of the ecliptic, including all apparent positions of the sun, moon, and most familiar planets. It is divided into twelve equal divisions or signs (Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, Pisces)"
While there is a common misconception that the dates listed on your horoscope would be where the Sun moves through each one of the corresponding constellations, that's not really the case. This is because astronomy and astrology are a bit like a pair of sisters that look very similar but are not. Your "sign" is actually something that was defined roughly 2000 years ago by someone who was working with solstices and equinoxes, that is, the changing of the seasons, for the most part. Since then, the very slow movement of the Earth's axis changed those points, shifting them around 30° West, relative to the constellations.
Having said all of that, don't ask us about your sign changing, and Ophiuchus is a constellation, not a sign. We'll entertain quite a lot, but we're not quite edgy enough for that one. This is also not a particularly new rumor, but one that often makes the rounds even though by this logic: 88 actual constellations provides a hell of a lot of wiggle room.
Interesting sidenote, another translation of The Emerald Tablet comes from Isaac Newton,whose Three Laws of Motion would later be used to prove Bernoulli and later Fourier's wave equation in respect to The Superposition Principle. However, you can't deduce it from those three laws. It's complicated. The zodiac is not, just be sure your vibrations are proper.