45 years ago, Carl Sagan debunked astrology in 2 minutes using twins and a newspaper
“Astrology suggests a dangerous fatalism.”

Carl Sagan on astrology.
Astrology is the pseudoscientific study of the patterns in the stars and their alleged influence over individuals and history. It has existed as long as humans first gazed into the night sky, and it continues to fascinate people to this day. Currently, it's experiencing a renaissance with younger people after becoming a popular topic on social media.
“There’s some indication that cave art shows this idea that animals and things can be imbued with some kind of spirit form that then has an influence on you, and if you appease that spirit form, then you will have a successful hunt. That was taken over by the idea of divination, where you can actually look at things in nature and study them carefully, such as tea-leaf reading,” astronomer Sten Odenwald told Time.
An astrological chart and divination dice.via Canva/Photos
Even though humanity’s understanding of the cosmos has made astrology appear rather crude and outdated, some people still swear by the power of Mercury in retrograde or the return of Saturn to determine the course of their lives. A recent YouGov poll found that 27% of Americans, including 37% of those under 30, believe that the position of the stars and planets influences their lives.
Although there’s something magical about having one's fate intertwined with the movement of celestial objects, it’s not a very logical way to go through life. In fact, Carl Sagan quickly disproved astrology in a 1980 episode of Cosmos: A Personal Journey. Sagan, the “Showman of Science,” is one of the world's greatest science communicators. At the time, Cosmos was seen by over 500 million people, making it the most-watched show in public television history.
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Carl Sagan believed that astrology is dangerous.
“[Astrology] seems to lend a cosmic significance to the routine of our daily lives. It pretends to satisfy our longing to feel personally connected with the universe. Astrology suggests a dangerous fatalism. If our lives are controlled by a set of traffic signals in the sky. Why try to change anything?” Sagan asked.
How to disprove astrology
Sagan used two simple methods to disprove astrology. The first was by looking at competing astrological forecasts in two newspapers, the New York Post and the New York Daily News. The Post's forecast for Libra said that “compromise will help ease tension.” However, the forecast for Libra in the Daily News suggests the opposite: “Demand more of yourself.”
“It's interesting that these predictions are not predictions, they tell you what to do, they don't say what's going to happen,” Sagan said. “They're consciously designed to be so vague that it could apply to anybody, and they disagree with each other.”
Sagan shot more holes into astrology by noting that if he had a twin, born on the same day, nearly at the same time, with the exact same astrological sign, they could have very different destinies. In the case of twins, one may die at a very young age from a horseback accident, while another may live a long and prosperous life. Therefore, the astrological forecast would have to be incorrect for one of them. "If astrology were valid, how could we have such profoundly different fates?" Sagan asks.
Carl Sagan with NASA technology.via NASA/Wikimedia Commons
Ultimately, Sagan believes that looking towards the planets to find out where our lives are headed is a shallow way of connecting with the universe when our real connection goes right to the core of our being. “The desire to be connected with the cosmos reflects a profound reality, for we are connected not in the trivial ways that the pseudoscience of astrology promises but in the deep ways,” Sagan said. But what is this deeper connection Sagan is alluding to? He has shown that humans are made of the most incredible substance in the cosmos: starstuff.
“The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in our apple pies were made in the interiors of collapsing stars. We are made of starstuff,” Sagan famously said.