Every now and again an article NASA published a long time ago resurfaces, bringing with it insane panic among astrology lovers.

Astrologers get terribly infuriated by this ‘fake news’ especially coming from a reputable source like NASA.

Astrologers are well aware of astronomical phenomena surrounding our area of expertise – we wouldn’t be able to interpret planetary movements, ingresses, retrogrades, or eclipses without this astronomical ‘add-on’ to our skill-set.

➡️ Astrology and Astronomy used to be the same area of study once upon a time

So what are NASA talking about? And has your star-sign really changed?

For those of you freaking out that you star (sun) sign has changed and everything you thought you knew is a lie, don’t panic!

NASA are actually referring to a real thing called procession, which astrologers are well aware of.


I remember as a child being fascinated by the Tropics of Cancer and Capricorn on the globe I had in my bedroom. I suppose they captured my imagination as my Cancerian sister and I had our sun-signs printed on planet Earth! 

Why were our Zodiac signs so special that they got their own tropic line above and below the equator? I had no idea what a tropic was, perhaps if I had researched it then, I would have journeyed into astrology much sooner.

The Tropical Zodiac

So what are the tropics, and why are Cancer and Capricorn so special that they’re detailed on maps and globes while the other zodiac signs don’t get a mention?

The way it works (try to imagine it) is the four cardinal signs: Aries, Cancer, Libra, and Capricorn, form a cross over the wheel of the zodiac. Astrologers refer to these axes as the Ascendant–Descendant axis (left to right) and the Midheaven and Immum Coeli axis (top to bottom).

Image result for zodiac wheel cross
Image from Tarotica

When the sun enters Aries and Libra (opposite each other from left to right) we have the Spring and Autumn equinox. This is the point of the year where the Earth reaches her tipping point and we notice a change in the seasons and the amount of light in the days. 

90° away from Aries and Libra are Cancer and Capricorn (opposite each other from North to South on the cross). These are the solstice points marking the spot where the Earth reaches its maximum tipping point of 23.5° before wobbling back.

So, not only does the Earth rotate on its axis once every 24 hours (creating night and day) and making a full revolution of the Sun through the celestial belt every 365 days (the solar year) – it also wobbles from side to side spending six months leaning one way, and another six months leaning the other, creating Summer and Winter. 

Spatial Awareness

The Earth’s journey through the year can be tracked following Sun’s position through the ecliptic, which is the Earth’s equatorial belt extended out into space. The ecliptic has a backdrop of constellations which we all know as the Zodiac signs. 

Image result for ecliptic
Image from Hyperphysics

The equinoctial points are the halfway points between the Solstices. From a geocentric (Earth centred) perspective, these are the seasonal markers and we witness the cyclic year through changes in the seasons and changes in the amount of daylight hours. The closer to the equator you are, the less obvious this is, as fluctuations in light are less extreme throughout the year. 

The word tropical refers to the tropics which lie above and below the Earth’s equator at a latitude of 23°26′12.3″ North (Cancer) and South (Capricorn) of the equator, referring to the maximum angle that the earth tilts during the solar year.

From the Spring to the Autumn equinox, the northern hemisphere tilts toward the sun. The tropic of Cancer is a hypothetical line around the northern hemisphere, which marks the farthest point the Earth tilts south towards the equator.

When the Earth reaches this point in tilt, we experience the longest day of summer in the northern hemisphere (and the shortest day of winter in the southern hemisphere).

From the Autumn to Spring equinox, the Southern hemisphere tilts toward the sun. The tropic of Capricorn is a hypothetical line around the southern hemisphere, which marks the farthest point the Earth tilts north towards the equator.

In a nutshell, the tropical zodiac uses the Zodiac signs and pins the four cardinal points to the seasons, coinciding with the Gregorian calendar.

Related image
Image from Buckingham STEM
Image result for tropic of cancer
Image from study.com

The Sidereal Zodiac

So now we’ve established the definition of the tropical zodiac, is it any wonder why so many people get freaked out when media outlets claim the constellations have moved and everyone’s zodiac sign is incorrect?

What the media spin-doctors are referring to is axial precession, which astrologers are very aware of! The fact is some astrologers use the sidereal zodiac which takes precession into consideration when making chart calculations.

Where the tropical zodiac is most commonly used by Western astrologers (like myself) Vedic astrology is an Eastern system using the sidereal zodiac. According to Vedic astrology, I am actually a Sagittarius, not a Capricorn!

Sidereal time is a system which astronomers use to locate celestial objects. However, this differs from the sidereal zodiac in astrology, and according to The Cynster:

“The longitudinal origin in the sidereal system is defined relative to the fixed stars. Fixed is used loosely here as some stars move. This movement isn’t immediately apparent but can be realized by tracking the position of stars over thousands of years.”

https://thecynster.home.blog/

The Sidereal Zodiac takes into consideration the precession of the equinoxes (or axial precession as astronomers refer to it). The original discovery of precession dates back to Hellenistic Greece, where Hipparchus compared the astronomical observations of his predecessors and discovered that fixed star Spica had moved 2° relative to the autumnal equinox over the space of a few hundred years.

“In astronomy, axial precession is a gravity-induced, slow, and continuous change in the orientation of an astronomical body’s rotational axis. In particular, it can refer to the gradual shift in the orientation of Earth’s axis of rotation in a cycle of approximately 25,772 years.”

Wikipedia

Over time, the equinox points and the zodiac have been travelling westward along the ecliptic with respect to the fixed stars. This means that we do not have a ‘fixed’ north star as the celestial poles appear to move in circles against the backdrop of fixed stars, completing one circuit in approximately 26,000 years.

“The apparent position of the Sun relative to the backdrop of the stars at some seasonally fixed time slowly regresses a full 360° through all twelve traditional constellations of the zodiac, at the rate of about 50.3 seconds of arc per year, or 1 degree every 71.6 years.

At present, the rate of precession corresponds to a period of 25,772 years, but the rate itself varies somewhat with time…so one cannot say that in exactly 25,772 years the earth’s axis will be back to where it is now.”

Wikipedia

So Which System Is Correct?

There are many big debates over the superiority of each system – I am not trying to resolve that conflict. In the same way we can look at the different house systems and how they work when interpreting the natal chart, both zodiacs are worth investigating to satisfy your own curiosity.

The main difference is that the sidereal zodiac uses the constellations and the tropical zodiac uses the zodiac signs.

However, it is worth acknowledging this statement (which was initially written about the different house systems) when embarking on your journey of zodiacal discovery:

“There is no definitive way to read a chart. With a good vocabulary and technique, all roads can lead to Rome.”

Frank C Clifford


➡️ Read Five Classic Reactions When I Tell People I’m An Astrologer

➡️ Read The Best Astrology Books for Beginners in 2020

➡️ Learn Astrology with The Stellium Astrology Podcast