We all get it. You’re a Capricorn or a Taurus or a Sagittarius or a(n) [any other zodiac constellation]. You’ve read all of your horoscopes, and they fit your personality soooo well. “This is so me,” you might yell to your friends, completely disregarding the fact that they don’t care which vague internet prediction you identify with. Aside from the many (and I mean, many) reasons that your horoscope is meaningless, the zodiac sign that you think is associated with your birthday is probably wrong. Read on to find the correct sign to freak out about as I debunk this and 2 other misconceptions people have about the night-sky.
- Your Zodiac Sign is wrong:
Depending on if you like to skip reading the title of blog posts, this fact may surprise you.
For those readers who don’t know, your zodiac sign is supposed to correspond to the constellation that the sun appears in on the day you were born. (This is also why some people call them “sun signs.”) And if you were born on May 12th, your zodiac sign would be the constellation Taurus–about 3,000 years ago.
The constellations shift positions in the night-sky throughout the year as our perceptions change with our orbit around the sun. Because our position around the sun changes, our perceptions of which star system is closest to the sun changes, making it appear as if the constellations are moving from month to month. So this is why we have different zodiac signs to start with. But why was your sign right 3,000 years ago but wrong today?
To get to the actual scientific reason your horoscope just got a little bit more meaningless we have to imagine the Earth’s behavior as it rotates around on its 23.5 degree tilted axis. Just like a spinning top, the Earth precesses as it rotates on its axis. Precession is caused by gravity’s effect on a tilted rotating object, causing it to wobble. Gravity from the sun and the moon tries to pull the Earth away from its tilt and into the ecliptic plane, which is basically just a straight line from the Sun to the Earth. (The ecliptic plane is actually what the Earth is tilted away from.) These gravitational tugs from the Sun and the Moon would work and straighten Earth’s tilt, but the law of conservation of angular momentum keeps it rotating along the same axis. Now that we have the science out of the way, let’s get back to what really matters.
A diagram showing the Earth’s precession next to the top. It also shows why the North star (Polaris) won’t be the North star forever.
The Earth’s precession is much, much slower than the rate at which it spins, taking about 26,000 years to complete one full rotation. Because the Earth’s perception changes as it precesses, the constellations that the sun appears in also change, similar to the ways in which they change throughout the year, but during a much larger timescale. The Earth’s precession combined with the fact that the Zodiac Astrological signs were devised around 3,000 years ago means that your sign is off by about a month. (Because we are about 1/13th of the way through the precession cycle).
Here is a list (taken from LiveScience.com) of all the zodiac signs with the correct dates (and a brand new sign!). Follow this link to read more on the Earth’s precession and its effect on our night-time view.
Capricorn – Jan 20 to Feb 16
Aquarius – Feb 16 to Mar 11
Pisces – Mar 11 to Apr 18
Aries – Apr 18 to May 13
Taurus – May 13 to Jun 21
Gemini – Jun 21 to Jul 20
Cancer – Jul 20 to Aug 10
Leo – Aug 10 to Sep 16
Virgo – Sep 16 to Oct 30
Libra – Oct 30 to Nov 23
Scorpius – Nov 23 to Nov 29
Ophiuchus – Nov 29 to Dec 17
Sagittarius – Dec 17 to Jan 20
2. The Reason for the Seasons:
While we’re discussing the tilt of the Earth’s axis, I want to briefly point out another common misconception that many people who snoozed through 4th grade science class have about the seasons. A lot of people think that the seasons are caused by variations in Earth’s distance from the Sun. It makes sense right? The Sun is a big ball of fire (also false, but that’s an entirely different post!), so the farther you get away, the colder you get, and vice versa. While it is true that distance from the Sun affects temperature (why you’ll need some serious sunscreen to visit Mercury and a winter jacket to visit Pluto), the Earth’s distance to the sun is almost circular. And any variation is so small when compared to the overall distance to the Sun that we don’t feel any changes here on Earth.
So if it’s not distance what does cause you to need a jacket in December? If you were paying attention to context clues, you can probably guess: the Earth’s tilt. Because the Earth is tilted on its axis, there variations in the amount of sunlight that each hemisphere receives depending on our position along the orbit. For the same reason that a flashlight shining perpendicular to a wall will appear brighter than if it was shone on an angled surface, the tilt of the Earth affects the strength of sunlight.
The diagram below shows this effect on the Northern hemisphere.
When a hemisphere is tilted towards the sun, that hemisphere experiences summer. When it is tilted away from the sun, it will experience winter. This is why the two hemispheres experience opposite seasons from each other, because one hemisphere is always tilted toward the Earth while the other is tilted away. We experience Fall and Spring when the Earth is in such a position that neither hemisphere is tilted toward or away from the Sun.
3. Is the Sun is directly overhead at high noon?
You hear this one all the time. Anytime someone is asked, when is the sky directly overhead in the sky, they answer with, “at noon.” But this a common misconception. The sun does reach its highest altitude at high noon, when it crosses the meridian (but even this is rarely directly at 12:00). Unless you live around the Equator (between 23.5 degrees South and 23.5 degrees North) the sun is never directly overhead.
Have you ever fallen victim to any of these common misconceptions? Want to tell me why horoscopes matter? What other misconceptions have you noticed that people have about space? Leave a comment below.
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