Astrology is bullsh*t. NASA's scathing takedown perfectly explains why.

NASA has had enough of this astrology crap. 

Astronomers have spent years patiently trying to explain why zodiac signs are not science, and NASA finally seems fed up with the public's obsession with them. NASA just dropped the ultimate astrology smackdown in a Tumblr post that's since gone viral. 

This post comes in the wake of an earlier NASA story explaining that your zodiac sign, or the constellation lined up with the sun at the time you were born, is probably not the one you thought it was. People got pissed and accused NASA of changing the zodiac.

Not so. "We didn't change any zodiac signs, we just did the math," NASA explained on Tumblr.

Astrology vs. astronomy

First, NASA laid out the difference between astrology (wacky pseudoscience) and astronomy (real science).

Astronomy is the scientific study of everything in outer space. Astronomers and other scientists know that stars many light years away have no effect on the ordinary activities of humans on Earth. 

Then, NASA explained the actual science behind the zodiac. Astrology is rooted in the idea that your zodiac sign can actually influence your personality or future. But the zodiac is actually just constellations of stars beyond the sun that we can see from Earth as we orbit.

Roughly 3,000 years ago, the Babylonians picked 12 constellations and assigned one to each month of the year. Turns out, that early estimate doesn't hold up to modern astronomical observations.

Here's the math NASA used

Earth's axis has shifted since the concept of the zodiac was first invented, so the constellations don't correspond to the same time periods anymore.

"When the Babylonians first invented the 12 signs of zodiac, a birthday between about July 23 and August 22 meant being born under the constellation Leo," NASA wrote. "Now, 3,000 years later, the sky has shifted because Earth's axis (North Pole) doesn't point in quite the same direction."

What's more, the Babylonians completely ignored a 13th constellation, called Ophiuchus, in order to preserve their 12-month calendar. 

They also failed to realize the sun doesn't spend an equal amount of time lined up with each constellation, so each constellation doesn't fit neatly into a one-month period.

"The constellations are different sizes and shapes, so the sun spends different lengths of time lined up with each one," NASA explained. "The line from Earth through the sun points to Virgo for 45 days, but it points to Scorpius for only seven days." 

NASA out.

If you know anyone who's ever blamed their misfortune on Mercury being in retrograde, please direct their attention here.