Carl Sagan on 'Cosmos'
Over the past few years, there has been a growing number of people who believe the Earth is flat. A 2019 YouGov survey of more than 8,000 Americans found that as many as one in six are "not entirely certain the world is round."
Flat Earth Theory has, surprisingly, gained a lot of traction. A 2021 study published in the National Library of Medicine posited that the theory is buoyed by "the cognitive tendency to interpret, favor, and recall information in order to strengthen one's personal beliefs" or, in other words, confirmation bias. Though the "how" and "why" of Flat Earth Theory and its popularity is fascinating (and troubling, to be honest), the scientifically proven truth is that the Earth is round. It is a globe. It is spherical.
Of course, the knowledge that the Earth is round is not new. Ancient Greek philosophers across centuries studied and found evidence that the Earth is indeed round thousands of years ago. Way back in the 6th century BC, Pythagoras first proposed the Earth was round from observing the shape of the Moon. In the 5th century, Empedocles and Anaxagoras noticed evidence of the Earth's true shape by observing its curved shadow during lunar eclipses. In the 4th century, Aristotle argued the Earth was round after noting how ships disappear "hull-first" over the horizon line. In the 3rd century, Eratosthenes actually calculated the Earth's circumference using geometry and shadows with shocking accuracy.
We've got the whole (round) world in our hands. Image via Canva
Naysayers remain skeptical, and there's probably no changing their minds, but to this day, experts insist the Earth is round and back it up with cold, hard science. NASA posted this video just days ago. Watch:
- YouTubewww.youtube.com
Here's where Carl Sagan comes in.
Sagan hosted the original version of TV's Cosmos: A Personal Journey in 1980-81. According to PBS, Cosmos would become "one of the highest-rated programs in the history of public television" largely due to Sagan's ability for "reinterpreting intricate scientific jargon into elegant and memorable statements that the common person can easily conceptualize and appreciate." The show would be revived in 2014 with astrophysicist Neil deGrasse Tyson at the helm.
In the first episode of Cosmos, Sagan easily proved the Earth was a sphere using a piece of cardboard, some sticks, and the work of none other than the ancient Libyan-Greek scholar, Eratosthenes. Watch:
- YouTubewww.youtube.com
"How could it be, that at the same moment, a stick in Syene would cast no shadow and a stick in Alexandria, 800 km to the north, would cast a very definite shadow?" Sagan asked. "The only answer was that the surface of the Earth is curved," he concluded. "Not only that, but the greater the curvature, the bigger the difference in the length of the shadows."
Considering the distance between the two cities and the lengths of the shadows they produced, Eratosthenes was able to determine that the Earth had a seven-degree curve. He used that calculation to speculate the Earth was 25,000 miles in circumference.
These days, we know that the earth is 24,901 miles in circumference, which means Eratosthenes was less than 100 miles off. Didn't we say his accuracy was shocking? Not bad for over 2,000 years ago.
This article originally appeared five years ago.
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