Recently, I was having a beer with some friends and the topic of birthdays arose. Somewhat inevitably, the subject of “birth signs” came up. I was born in October, so (apparently) I was born “in” Libra, and (apparently) that says something profound about me. I beg to differ, but (apparently) that’s a Libran trait as well, so I’ll lay out my case here for your consideration.

Our conversation was very much in jest, and light hearted, but it got me thinking about horrorscopes – hmmm, I’m sure I’ve spelt that correctly, but spellcheck doesn’t seem to agree 🙂

Like most good counterfeits, there’s a grain of truth in the base concept behind horrorscopes, and that is that the heavens can be used to track important events. Before the advent of calendars, knowing when to sow seed or when to conduct the harvest was important, and the position of certain stars at at certain times of year became a helpful guide in this regard. But horrorscopes are no more credible than chinese fortune cookies.

For something that has no basis in reality, the whole topic of horoscopes (sp) is hideously complex and convoluted. For the purpose of this blog post, I’m going to go with the simplest version most people are familiar with culturally, that of horoscopes being based loosely on when someone was born.

Zodiac symbols making up constellations outline the earth and create the Zodiac. As they revolve around the earth, the signs become event markers – Daily Horoscopes

The Zodiac does not “revolve around the earth,” rather Earth spins on its axis each day as it revolves around the Sun each year. This statement is five hundred years out of date.

One of the many technical problems with astrology is the notion of constellations of the Zodiac being important around sunrise. Somewhat ironically, this means these stars are furtherest away.

If the constellations of the Zodiac held any influence over our lives, their influence would be less at that time of year, not greater. If anything, they should exert their greatest influence when they appear directly overhead at midnight, as that’s when they’re closest.

But the distances involved are so extreme compared to Earth’s orbit of the sun that our orbit never equates to more than a fraction of the overall distance. Alpha Centauri, as an example, is the closest star outside our solar system. At 25 trillion miles, our orbit around the sun equates to 0.000006% of the distance to Alpha Centauri. If there was any celestial influence over our earthly lives from these stars it would be static and unchanging regardless of where the constellation appeared.

Astrologers use the Zodiac to learn about people’s futures and how they react to life. For them, the Zodiac is the roadmap of people’s lives – Daily Horoscopes

Such a modest claim for a concept that is as thin as tissue paper. It will come as no surprise to learn there’s no scientific basis to astrology.

The scientific method is simple. There’s nothing mysterious or mystical about science. Does an idea live up to its claim when scrutinized in detail? In essence, that’s all science is.

The premise that celestial events influence earthly events has been shown to be false.

Astrology fails to recognize that the stars we see appear as though they are all the same distance from us, but this is a line of sight illusion.

Stand on a street and look at the telephone poles stretching into the distance. Those further away appear much closer that those you see next to you even though they’re all evenly spaced. In the same way, two stars may appear close together in a particular constellation but can be separated by a greater depth of distance than two stars that appear to be spread apart in different constellations.

In this image, stars from several Zodiac constellations are clustered relatively close to our sun, while the vast majority of the hundreds of stars making up these constellations (as seen from our perspective on Earth) are thousands of light years away.

solar-centric perspective destroys the illusion of the Zodiac.

Ah… but it gets worse… You’re probably familiar with these dates

Zodiac Sign Dates
Aries The Ram March 21 to April 20.
Taurus The Bull April 21 to May 20.
Gemini The Twins May 21 to June 20.
Cancer The Crab June 21 to July 21.
Leo The Lion July 22 to August 22.
Virgo The Virgin August 23 to September 22.
Libra The Scales September 23 to October 22.
Scorpio The Scorpion October 23 to November 21.
Sagittarius The Archer November 22 to December 21.
Capricorn The Fish-Tailed Goat December 22 to January 20.
Aquarius The Water Bearer January 21 to February 19.
Pisces The Fish February 20 to March 20.

The problem is… they’re all wrong.

The Zodiac was drawn up around two thousand years ago, when these dates coincided with the correct location of these constellations in the sky. Since then, the precession of Earth, its slow “wobble” through space, has caused these dates to shift.

If you’ve never heard of precession it might seem a little obscure, but Earth slowly precesses like a child’s spinning top. Although the top is spinning rapidly, its axis slowly points in a different direction over time.

Over a period of almost 26,000 years, Earth slowly points at a different point in outer space. Polaris hasn’t always been the pole star and won’t remain the pole star. The celestial north pole will drift as far as Vega due to precession.

Over the past two millennia, the slow precession of the equinoxes has caused the dates assigned to horoscopes to shift by roughly half a month.

Constellation Original Date Actual Date
Aries March 21 – April 20 April 15 – May 15
Taurus April 21 – May 20 May 16 – June 15
Gemini May 21 – June 20 June 16 – July 15
Cancer June 21 – July 21 July 16 – August 15
Leo July 22 – August 22 August 16 – September 15
Virgo August 23 – September 22 September 16 – October 15
Libra September 23 – October 22 October 16 – November 15
Scorpius October 23 – November 21 November 16 – December 15
Sagittarius November 22 – December 21 December 16 – January 14
Capricorn December 22 – January 20 January 15 – February 14
Aquarius January 21 – February 19 February 15 – March 14
Pisces February 20 – March 20 March 15 – April 14

And that’s a rather long-winded way of pointing out that rather than being born “in Libra” I was actually born in Virgo… so what does that tell you about me? Hah!

23 thoughts on “Horrorscopes

  1. …well…i agree with some of your statements…but ive found that, surprisingly, some of the traits the zodiac signs mention, are indeed true…eg. librans are well known to be bad decision makers….too-ing and fro-ing before making decisions…just like a scale bobbibg left or right…how do you account for that?

    • You’ll find that same poor decision making spread throughout all the other “signs” as well. In fact, there was a study done that highlighted precisely this. Researchers in London tracked 2000 people all born within minutes of each other, following them for decades to see if they shared the same astrological traits. They didn’t. If astrology works as claimed then it should be something we can measure, but it doesn’t. And, if it works, the big question is how can it work if roughly half of the people alive have been assigned the wrong star sign, just as I was, lol.

      Thanks for the reblog 🙂

  2. I’ve never been able to pay attention to the nonsense of horoscopes, tea leaves reading and other such things.

    I find it hilarious to believe that one’s life is dictated by an imaginary correlation between stars on the visible sky that are not even related to each other, and are in fact tens of light-years distant from one another. Not to mention that the “constellation” we see in the sky on the day of our birth is made of light that originated from those stars thousands of years ago, when not a single of our direct ancestors even existed. Hard to imagine that radiation from distant stars influences the life of some poor bloke who happens to pop into existence when that light hits Earth one fine morning.

    • Ha… yeah, the time lag and line-of-sight issues kill the whole concept. It’s a good example of how science makes previously common beliefs obsolete… I don’t know how anyone ever saw a bull, a scorpion and a set of scales in the sky. I certainly don’t.

  3. The best proof that horoscopes are false is that Capricorns are suppossed to be handsome, sexy and incredibly smart. Now, according to the new charts I am supposed to be Saggitarius and I am still handsome, sexy and incredibly smart…. (;-)

  4. OK! You’ve officially blown my mind. There are certain traits that I feel fit within the astrological sign in which I thought I was born, but I don’t entirely fit the mold. Now, I know why. I love to read my horoscope, but I’ve usually forgotten what it was before I put the paper down. 🙂

  5. Reblogged this on Luis Batista "Amichi" and commented:
    My birthday is celebrated on July 11 since I was born on that month, but because I was registered one month later, on August 11, officially my anniversary is also celebrated on that month. So, I never know which zodiac sign to follow, and I get confused.
    This is to support your idea that there ’s no scientific basis to astrology. We need to be more rational.

  6. I’ll give astrologers a pass on their method of selecting which sign someone is “born under.” Sure, the stars in the sign in which the sun currently resides are farthest away, but it’s just a convention. A magnetic compass could be configured to point in any direction, but we use North because it’s convenient. Using the sun as a “needle” or clock hand among the stars is convenient, even if it indicates the stars that have the least amount of influence on us.

    I once read about a study done on astrology believers. If someone successfully guesses the color of a playing card (red or black) 50% of the time, astrology believers are more likely to conclude that such a high percentage of accurate guessing can’t be coincidental, and some form of telepathy (or something) must be at play. (Of course, we all know that 50% is the expected outcome from mere guessing.) In conversations I’ve had with astrology believers, they frequently punctuate their discussion with, “I KNEW IT!” whenever they encounter something — anything — that reinforces their beliefs, no matter how coincidental.

    As a consequence of this manner of thinking, there is a movement among some astrology believers to change the name of the sign of Cancer to something else, since fully one out of twelve cancer patients are born under the sign of Cancer, which can’t be mere coincidence, they are convinced. How does mere nomenclature influence the distribution of cancer diagnoses among the signs of the Zodiac? Who cares? Renaming the sign makes the problem go away, case closed. By renaming the Cancer sign to something else, the correlation doesn’t apply, so there’s no reinforcement making the coincidental stand out. It’s a mind trick that relies on suppressing the mere appearance of correlation without actually affecting anything that makes a difference.

    However, the plan might backfire due to their shortsighted choice for Cancer’s new name. What is the new name they’ve selected for Cancer? They’ve selected FLESH EATING BACTERIA.

    I know, right?

    • Ha… I just love the way the dates associated with astrology have slowly drifted over thousands of years and nobody noticed because it didn’t make any difference. lol. Imagine if the strength of gravity had slowly changed and no one noticed!

      • And this is a lost opportunity for astrologers. It’s the calendar — not astrology — that has drifted. Astrology is (or at least, arguably should be) sidereal, while our tropical calendar is anything but. If the stars have any influence over us at all, wouldn’t it be on a sidereal basis, and not on the basis of our arbitrary decision to keep equinoxes and solstices from drifting through the calendar?

        Astrologers had the opportunity to maintain sidereal integrity, but instead continued to base their zodiac on the shifting tropical calendar. Too bad. Sidereal consistency could have been the only claim to consistency astrology might have had, and they threw it away.

  7. Pingback: Android Astronomer » On Coincidence and Belief

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