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There has been a disturbance in the astrological forces.

What you think you know about the zodiac may be a lie. The sign you think you were born under is different, to hear astrology wonks tell it. The dates for the western zodiac calendar have compressed and shifted later by a few weeks: If you were a Virgo born before mid-September, so the story goes, you are a Leo (now Aug. 10 to Sept. 16). Congratulations!

There is a thirteenth sign, too — Ophiuchus. People born between Nov. 29 and Dec. 17 are Ophiuchuses. (Your new talents include architecture and snake-bearing.) With all of the chaos in the heavens, one might think that a retrograde Mercury is to blame.

But there is no rogue planet at fault. Just an informative blog post aimed at children.

In January, NASA wrote a brief history of how the western zodiac came to be. The zodiac is grounded in history more than science. In short, the Babylonians created the zodiac as we know it about 3,000 years ago. Imagine a laser beam that shoots from Earth, through the noon sun and into constellations of stars beyond. (These constellations are patterns that the Babylonians decided looked like animals or people.) The dates of the zodiac calendar follow this laser line as it sweeps from constellation to neighboring constellation, a bit like the hand of a clock.

The calendar did not translate to the stars perfectly. The ancient astrologers only had 12 months to work with, but the sun passed through 13 large Babylonian constellations. So they deleted one. Although the city of Babylon collapsed under the weight of being conquered repeatedly, this lean, Ophiuchus-less zodiac endured.

Its imperfections did, too. The ancient Babylonians knew enough to track the sun’s path through the sky, but they were unaware that their reference point on Earth was unstable. Unlike a globe, the planet does not spin perfectly about its axis — there is no stake through molten core pinning the north pole in place.

In fact, Earth’s north pole has progressed eastward since 2000, at a rate of about 7 inches a year. By geologic standards it is a dramatic lean. Recent scientific studies indicate that climate change is rearranging the planet’s watery bulk, pulling Earth to the side. NASA’s Jet Propulsion Laboratory recently implicated droughts in Eurasia, in India and around the Caspian Sea. But much of the change is due to lost ice. “Greenland is the lion’s share of the mass loss,” University of Texas at Austin researcher John Ries told Scientific American in April. “That’s what’s causing the pole to change its nature.”

And because Babylonian astrology depends on the location of Earth, sun and star constellations, NASA pointed out the clock hand of the zodiac has been wound back. “Now Mimi’s August 4 birthday would mean she was born ‘under the sign’ of Cancer (one constellation ‘earlier’), not Leo,” NASA wrote in January.

In mid-September, Cosmopolitan UK ran with the story. Reactions varied. Zodiac tattoo bearers lamented their now-obsolete tats. Ophiuchus was deemed unpronounceable. Others chose to ignore the changes and stick to the 12 signs they are used to.

Nor is this the first time Ophiuchus and a shifting axis have thrown the zodiac into limbo. In 2011, the Minnesota Star Tribune reported on the wobble’s astrological impact and the not-so-lost sign. (The Washington Post wondered whether Taylor Swift was best served as a Scorpio, Ophiuchus or Sagittarius, deciding she could be all of them.)

This time around, NASA took to its Tumblr account to clarify that it did not set out to blow up anyone’s astrological calendar.

“Here at NASA, we study astronomy, not astrology,” the space agency wrote in a statement Tuesday. “We didn’t change any zodiac signs, we just did the math.”

NASA’s ultimate counterargument is that the zodiac calendar is a fantasy on par with a fortune cookie. Fun and a little funky, perhaps, but in no way life-changing.

There is a brief but convincing history of scientists investigating, and failing to prove, astrological claims. In a double-blind experiment published in 1985 in the journal Nature, Shawn Carlson, a researcher at the University of California at Berkeley tasked 28 astrologers with matching tests. Volunteers filled out a personality survey and provided their birth information. Carlson, after removing the volunteers’ identities, had astrologers match the surveys with a corresponding astrological birth chart.

The results indicated the astrologers fared no better than chance. “We are now in a position to argue a surprisingly strong case against natal astrology as practiced by reputable astrologers,” Carlson concluded.

Distant constellations, or even planets in our solar system, do not emit any known forces that could have a dramatic and personal effect on our lives, pointed out astronomer and science writer Phil Plait. If gravity ruled astrology, the moon would far overpower any other heavenly body, he noted. Likewise, if electromagnetic forces were the culprit, everything but the awesome power of the sun could be discounted. Nothing else in the heavens really comes close.

And if you are worried about the next time Mercury is in retrograde, breathe easy. The planet seems to change direction — traveling east to west rather than west to east — as matter of perspective on Earth, not orbital pinball. (It’s akin to the way a car appears to move backward from a fast train, even if car and train are moving in the same direction.) Contrary to pop astrology, Mercury has no bearing on your electronics.

The altered zodiac calendar, via Cosmopolitan UK:

Capricorn: Jan. 20 to Feb. 16
Aquarius: Feb. 16 to March 11
Pisces: March 11 to April 18
Aries: April 18 to May 13
Taurus: May 13 to June 21
Gemini: June 21 to July 20
Cancer: July 20 to Aug. 10
Leo: Aug. 10 to Sept. 16
Virgo: Sept. 16 to Oct. 30
Libra: Oct. 30 to Nov. 23
Scorpio: Nov. 23 to Nov. 29
Ophiuchus: Nov. 29 to Dec. 17
Sagittarius: Dec. 17 to Jan. 20