How The Ancient Greeks Knew That The Earth Was Round
Sponsored link:
Not only did the Ancient Greeks know that the Earth was round - they even figured out the circumference of the Earth to high precision over 2,200 years ago.
Sponsored link:
Astronoimer Carl Sagan explains how they did it, just using two sticks.
Eratosthenes of Cyrene (276 BC – 194 BC) was a Greek mathematician, geographer, poet, astronomer, and music theorist.
He was a man of learning and the chief librarian at the Library of Alexandria.
Eratosthenes calculated the circumference of the Earth without leaving Egypt. Eratosthenes knew that at local noon on the summer solstice in the Ancient Egyptian city of Syene (now Aswan) on the Tropic of Cancer, the Sun would appear at the zenith, directly overhead. He knew this because he had been told that the shadow of someone looking down a deep well in Syene would block the reflection of the Sun at noon off the water at the bottom of the well. Using a sundial, he measured the Sun's angle of elevation at noon on the solstice in Alexandria, and found it to be 1/50th of a circle (7°12') south of the zenith. He may have used a compass to measure the angle of the shadow cast by the Sun. Assuming that the Earth was spherical (360°), and that Alexandria was due north of Syene, he concluded that the meridian (longitudinal) arc distance from Alexandria to Syene must therefore be 1/50th of a circle's circumference. Wiki
But how did he know the sun was so far away that its rays were parallel? Here is how the ancient Greeks figured out the distances to the Sun and Moon: Wiki
Eratosthenes calculated the circumference of the Earth without leaving Egypt. Eratosthenes knew that at local noon on the summer solstice in the Ancient Egyptian city of Syene (now Aswan) on the Tropic of Cancer, the Sun would appear at the zenith, directly overhead. He knew this because he had been told that the shadow of someone looking down a deep well in Syene would block the reflection of the Sun at noon off the water at the bottom of the well. Using a sundial, he measured the Sun's angle of elevation at noon on the solstice in Alexandria, and found it to be 1/50th of a circle (7°12') south of the zenith. He may have used a compass to measure the angle of the shadow cast by the Sun. Assuming that the Earth was spherical (360°), and that Alexandria was due north of Syene, he concluded that the meridian (longitudinal) arc distance from Alexandria to Syene must therefore be 1/50th of a circle's circumference. Wiki
But how did he know the sun was so far away that its rays were parallel? Here is how the ancient Greeks figured out the distances to the Sun and Moon: Wiki
Flixxy editors search the internet daily, to find the very best videos for you:
SELECTION: From over 3 million videos uploaded to YouTube daily, we select only a few videos to be added to the site daily.
PG RATING: Flixxy videos and comments are all PG rated. They are "Safe For All Ages" and "Safe For Work". Our content is uplifting.
SELECTED START AND END POINTS: Many of Flixxy’s videos start late or end early. We skip lengthy introductions and get to the point.
CONCISE CAPTION AND DESCRIPTION: We don't use "click-bait." Your time is valuable, so we distill the information down to what you want to know.
FREE DAILY NEWSLETTER: Get the latest videos delivered to your inbox by subscribing to the FREE "Video of the Day" newsletter.
FREE DAILY NEWSLETTER: Get the latest videos delivered to your inbox by subscribing to the FREE "Video of the Day" newsletter.
Sponsored link: