Carl Sagan explains Eratosthenes' calculation about round Earth #space #sciencefacts

Greek Mathematician Eratosthenes calculation

[chaz]

This short is criminally short.

Eratosthenes went a step further and measured the shadow at Alexandria, then hired a courier to precisely measure the distance between Alexandria and Souan. Using those two pieces of information: he was able to perform a calculation to determine the approximate size of the earth.

He was between 2.4 and 0.8% off.

He was known among his colleagues as Πένταθλος, or an "All Rounder". A true polymath.

[prof_jesus]

Carl Sagan was absolutely superb. He had this amazing talent of educating others without sounding condescending or demeaning towards those who do not know. He did so precariously and with tact. He was polite and was never prone to lash out impatiently.

[Bozolips]

I love Carl Sagan's life lessons, he was truly a fantastic teacher

[fatpoorvagrant]

It's amazing that ancient civilizations were smarter than modern day flat-earth YouTubers.

[chernobyl]

I'm telling you, the world needs way more Carl Sagans around.

[jayknuffke]

Flat earthers: "I replace your proof and logic with my own fantasy."

[FuneFox]

"Math is useless!"

10 years later: "The earth is flat!"

[Polycarpio]

The guy shouting from obelisk to obelisk is the real MVP

[andy.hello.]

If we are arguing this in 2023 we are fucked.

[timmckeown]

Eratosthenes also calculated the circumference of the earth almost precisely by calculating the distance between those two cities and extrapolating from there. Brilliant.

[samuelcapritta]

I love the way he talks and gives credit to the ancient science!

[keithfernandez]

I grew up with Carl ...I miss his Knowledge and Teachings !!

[TheGreatSeraphim]

They didn't just figure out the earth was curved they almost perfectly calculated its circumference with this information.

[patcomerford]

Carl Sagan was one of the greatest teachers we have been blessed with. Thank you for this upload.

[lorenzop]

For anyone wondering how they knew it was the same time, well, sundials were a thing
if you move only in latitude but keep about the same longitude the sundial will indicate about the same time (same principle of time zones)
so they just took a measure of the shadow at the same indicated time.

[johnnyguinn]

Try explaining this to the flat earthers.

[markgigiel]

Hey Carl, we need ya back. We have regressed since you left.

[vijaynair]

Carl explained things so calmly and simply.
Not like Neil DeGrasse Tyson who constantly cuts people off and pauses for dramatic effect.

[nalvarado]

I think the most confusing part left out is how they communicated this information instantly to each other. The answer is they didn't. On the summer solstice the sun was directly overhead in one town and a stick cast no shadow. At noon in the other town (that is the other town's noon) a stick did cast a shadow. That information can be relayed at their leisure.

[jamesalexander]

His tools were basic at the time but Carl Sagan taught millions of us the science of space in the simplest way even a 5 year old could understand. His calm approach was hypnotizing It's why Dr. Sagan is sorely missed.