Eratosthenes is damn genius. But lets get a moment of silence and respect to the man he hired to walk 800 km.

I legit get chills when Sagan says "that's the right answer". It's such a simple feat but what a thing to work out so long ago with the most basic of tools.

Single handedly brought Astronomy/Astrophysics to the laymen. His ability to explain things in laymen's terms was amazing.

The funny thing is that Eratosthenes did this with his eyes and a couple of sticks, but on present days when we're launching rockets into space and flying around the world, flat earthers still can't figure out

I could listen to Carl Sagan talk about paint drying.

After all these years with no fancy graphics or animation, Carl still explains it the best using simple props

If every school in the world had a science teacher like Carl Sagan, the human race would have explored the whole solar system by now, and we would be reaching for the galaxies. We will never make up for his loss.

Nobody presents Cosmos like Carl Sagan. He was amazing.

I wish todays documentaries had subtle sound design and smart writing like these old ones.

Although as a teenager I didn't like documentaries, as I found them boring, I was fascinated by Carl Sagan. This man made me understand that all the things that my teachers were teaching me in different subjects were connected , that everything had to do with everything. And that was when learning became meaningful.

A guy 2200 years ago hears a story about the shadow of a pillar, thinks for a little while on the implications, devises an experiment to confirm those implications, and successfully carries out that experiment. Now, 2200 years later, there are people handed all this information on a silver platter, and at literally 100+ times the precision and evidence, and somehow still fall far short.

I remember my Earth Science teacher telling my classmates and I about Erastothenes back when I was in the ninth grade. This was in 1978. More than anything else, this lesson stayed with me through the years. Mr. Prewitt, thank you sir.

This guy blew my mind when I was a kid and became one of my heroes! Too bad he is no longer with us.

Cosmos, one of the best series ever on television. I’m afraid it would never happen again.

My dad watched this as a teenager in 1980 and I watched it a teenager in the 2010's. I was completely captivated. Sagan’s storytelling, the ideas is explored, and the beautiful music from Vangelis come together perfectly to make a true masterpiece. Carl Sagan has been my hero ever since and I enjoy coming back to rewatch the series from time to time. It just goes to show that you don't need a big budget and fancy graphics to create a truly captivating series.

Carl has the most mesmerizing voice I have ever heard.

"His only tools were sticks, eyes, feet, and brains."

One of the best programs ever. Imo…RIP, Carl Sagan…

Watching this in 2020 , man I miss Carl Sagan. This is the kind of thing that made me persue my education.

Keeping an accurate pace count over a vast distance in a more or less featureless desert, is quite an achievement in its own right. I have a lot of experience in land navigation from my time in the Army, and even with a compass, protractor, and pace beads, keeping an accurate pace count whilst navigating is not an easy task. Kudos to that unsung man!

I've watched this many times over the past years. 6:00 "That's the right answer" always gets me. This is what I turn to, whenever feel I need to regain my hope for humanity. It's very bitter sweet to know, that even though all the world is crazy, there is still hope for vindication far beyond my lifetime.

I remember watching this as a kid. I can can think of no other show in my childhood that had such a profound impact on me. I recorded it (on Betamax) and watched it over and over again.

The name of this man was so important to me since I was a little girl...I still get ''goosebumps'' about this.

Carl Sagan is the Santa Claus of Science, turning knowledge into an enjoyably precious gift for all.

I think the guy who paced out 800km straight as possible deserves the credit for the accuracy.

Praise be Saint Carl!

Carl Sagan once predicted on a talk show that in the future our attention would be taken by 8 to 10 second soundbites.. he was way ahead of his time.

Eratosthenes was a genius by far but let's pay some respect to that dude that wrote that scroll in the first place!!

This is a very appropriate segment in terms of speaking to the main reason that Carl Sagan created this series. In spite of vast technological advance, he always, always was a proponent of the capacity and capability of the human intellect. He spoke several times during the series referencing Alexandria, the intellectual powerhouse that it was, and the focal point of that ancient city being the wealth of knowledge contained in its great library. Carl recognized the fundamental and absolute importance and necessity of human intellect, and the collection and collaboration of its constituents. He also recognized the implications of its demise. Here, he is so happy to relate and relish in one of mankind’s finer moments. Carl Sagan’s incite into the human condition and intellect are unmatched. He was a treasure to us all.

A guy 2200 years ago figured this out with almost nothing and yet in the age of information and technology we still have people that think it's flat 🙄. No, I've never seen it with my own eyes, beyond just equations and satellite photos, but I trust the scientific community with this one.

Sagan: Eratosthenes only tools were sticks, eyes, feet, and brains. Flat Earthers: Damn, three out of four.

This is clearly one of the most brilliant moments ever shared with the public. Sagan's natural television presence made the heady topic of science easier to understand. In re-visiting this from my childhood, I am reminded of why I entered teaching. Watching Sagan share history like a story (such as his tale about Eratosthenes employing someone to pace out steps) makes it more appealing to youth, and inspires me to teach history in the same manner.

How about some love for the poor bastard who walked that straight line? What was his name, how much did he get paid?

Eratosthenes estimated the distance from Alexandria to Syene as 5,000 stadia, or about 500 miles (800 kilometers). He made this estimation from the time it took walkers, who were trained to measure distances by taking regular strides, to trek between the cities. -Khan Academy

Carl Sagan was/is so easy to listen to and hence interesting. He was a great educator.

Always enjoyed this tidbit of history. That is to say, tidbit, yes, but a one of monumental proportions! Loved Sagan in this era, never missed his shows or guest-appearances. He was right for his times, striking a chord with the public more than any other astrophysicist before or since. I mourned this "Star of the Stars" upon his passing & have never forgotten him.

Just love this! I remember watching Cosmos back in 1980--in my mid-teens then. Absolutely glued to it--the content, Sagan's presentational style, including the fiction of him being a cosmic traveler, the soundtrack (esp. Vangelis). A masterpiece of a series.

I enjoyed watching Carl Sagan in the Johnny Carson show, such a brilliant man. Also loved how Beethoven's 7th opens up this story.

the opening is so good. it always lightens my mood rewatching it.

God Bless Carl Sagan (and Bill Nye, the Science Guy!). Because of great men like Carl I have a son who is a Mechanical Engineer and a daughter who is an Elementary School Teacher. I enjoyed watching all these shows back in the 1980's when my kids were small. Literally Millions of kids eyes were opened to Science by Carl Sagan. From the smallest child to the old folks in the house we sat absorbed with interest and curiosity when Sagan spoke to us through the TV...

Having seen this episode when it was originally broadcast I asked myself "why didn't any of my teachers through elementary and high school ever tell this story?". That would have made science and/or history more real.

I remember Carl Sagan very well from when I was a youngster, he certainly helped to fire up my interest in astronomy, and his television series, Cosmos, was not only fascinating, beautiful, and educational, but groundbreaking. He was one of our greatest science communicators, speaking very wisely too, and he is sorely missed in these very uncertain times.

I love this series….Before Carl Sagan, the only real exposure to the cosmos came from occasional family trips to the Griffith Park Observatory when I was a child. Those trips created a fascination and thirst for more knowledge. I read encyclopedias, but the television series Cosmos really opened things up for me. Carl Sagan brought the Cosmos to myself and so many others, just ordinary people. I’m forever grateful.

I feel like this is the inspiration for Hugo Weaving's delivery as Agent Smith. The delivery is dead on.

I have read Cosmos 4 times over 30 years and just devour it every time. Dr. Sagan, just as Eratosthenes gave the world gifts of such incredible value. Humans will one day live for centuries, but how I wish that ability would have been available for people like these two.

I have to say Carl Sagan.............such great communicator and one of the greatest educators........

This man helped create the next generation of scientists. One of my other favourites Brian Cox always cited him as a great inspiration 😊

Eratosthenes - Chief Librarian of the greatest libraries in ancient times that contained knowledge now since lost to us. Yet -- I had never heard of him. What a shame. He should be just as well know as Socrates, Plato and other such giants of the ancient world.

I was never into science, but I never missed an episode of Cosmos. Carl Sagan was amazing in this series.

This must be one of televisions greatest moments.

This is classic Carl Sagan. I remember showing this to my Science students decades ago.

Me too. He was incredibly articulate and eloquent. I love every sentence!

He *gasp* PAID a man to pace and measure the distance between the two cities?! Nowadays you just get some poor grad student to do work like that lol

Astounding story and retelling, but what I'm most impressed by is Sagan's voice and accent. Does anyone speak like this anymore? The drawn out language, the phrasing ... it's from some place and time lost to us now except in recordings like this from the past.

I miss Carl Sagan , one of a kind 🇬🇧

This is the coolest thing ever

How sad would Sagan and Eratosthenes be to learn that nowadays flat earthers exist

At 1:05, this honorable champion is demonstrating, ~2300 years later, why you shouldn't burden yourself with the petty judgments of others. Sound logic stands the test of time.

I need that Carl Sagan drip. My boy fresh as hell

Totally love with this man he filled my mind with such Wonder. My mom got me a record of the soundtrack that I used to play as I drifted off to sleep such a wonderous world

Carl kept me impired as a child in 70s. I listened to all of his episodes

I so dearly wish we could get a modern remastering of this series, and maybe a home media release. I'd buy the hell out of it.

Carl Sagan changed my life. In the 1980’s, I watched Cosmos spellbound.

I watch this video a lot from time to time. It is, in my mind, the greatest story ever told.

Eratosthenes provided a highly accurate diameter of the Earth in 300 BC and then 1700 or so years later Christopher Columbus got it wrong by a gigantic amount thereby mistaking the islands of the Caribbean for India. Eratosthenes was an genius. Columbus was a buffoon.

It's time to watch Carl's "Cosmos" again.

These educational miniseries from 40, 50, 60+ years ago seem so much more effective to me than current ones. Cosmos with Carl Sagan, Civilisation with Kenneth Clark, Connections with James Burke. I have a college degree and each one of them has still taught me so many fascinating things in an easy to understand manner.

how beautifully explained. we need more Sagans!

One of the cool parts about living in a tropical region is seeing a Lahaina noon (time of no shadows). which by definition only happens in tropical regions. Therefore, we live on a round earth.

Mind blowing moment of realisation! Erasthothenes' sheer brilliance.

My favorite bit from Cosmos. This one part alone made me discover Science when I watched this in my teens

I saw this show when I was a little kid, and I still remember this segment vividly. This one and the one on Champollion and his decipherment of the hieroglyphics.

Great explanation of profesor Sagan.... and musical background magnificent Beethoven 7th symphony

THE only video you need to watch. This man was and is a legend! #cosmos

Our schools really desperately need to be teaching the history of science and technology. I'm so thankful I got brought up on programming like this that instilled in me the truth that our understanding of the world changes with each new day we spend on it!

My mum let me stay up really late to watch Cosmos, absolutely loved it 😍

Carl Sagan ... RIP !

The Greeks already knew the earth was probably round. Pythagoras had noticed that ships disappear over the horizon bottom first. I believe the Chinese did the same experiment but assumed the earth was flat but the sun was much closer. I believe they worked out that the sun was 3000 miles away and had a diameter of 28 miles or something like that. Flat Earthers use these measurements today. It was still amazing though that he came up with a pretty good estimate of the size of the planet way back then,

I watched this with the best of intentions every week at 10pm to finish the entire programme. I never ever got any further than 15 minutes in before nodding off with carls melodic voice and the ambient music.

I grow up in Argentina seeing Carl program's called Cosmos every week on TV.... This man is a Science Collosus...

Carl Sagan - Proves the Earth is round

meanwhile in the era of sattelites and rockets and internet...some people think the earth is flat, let that sink in on how much we regressed.

Carl Sagan is one of the people that if he lived 200 more years he would still be offering to mankind. Thank you for opening our eyes Carl Sagan.

Carl Sagan was one of the greatest men humanity will ever know.

Shout out to the person who was paid to measure a large distance and actually did their job.

“Here’s a bottle of water, a Cliff bar and some sunscreen. Get walking pace-boy” - Eratosthenes

Just started watching Carl Sagan. I heard of him a long time ago , if I knew he w as so interesting to listen to I would have been watching sooner. Good stuff.

2200 years ago, Eratosthenes proved earth's curvature but today people still believe that earth is flat

Flat Earthers: *"I'm going to pretend I didnt see that"*

Can you imagine *PACING* 800 km to a high degree of accuracy? That shit must have taken years!

I loved Cosmos so much. Dr.Sagan was totally fascinating.

This guy is great. Gotta love Sagan.

Back when you couldn't waste film and you couldn't make a mistake.

I found the Cosmos series in late 2019. Wonderful series with a great atmosphere and content.

6:13 "That's the right answer." Love it.

What a polite way to tell flat-earthers to catch their breath in the shadows and may be - if they can - learn something

Sagan glossed over a point that is intriguing and important. Eratosthenes recognized that the difference in the length of shadows cast, at a simultaneous moment, in Alexandria and Syene (Aswan) meant that the Earth’s surface was curved, not flat. But he knew that the differences in shadows cast at noon in different places •had• to mean that the Earth’s surface was curved, •because• the light source casting the shadows, the sun, was so immensely far from earth that its distance was, for purposes of these measurements, infinite. Put another way, the difference between the shadows in Alexandria and Syene •could• have been present on a flat Earth, if the sun were only some 4,000 miles away. And if you think about it, it wouldn’t be immediately obvious to a person in Classical Antiquity - who, like most humans through our species’ existence, knows of the world (and all existence) only what he observes immediately around him - that the sun is •not• just something like 4,000 miles away. Figuring out that the sun must be much, much farther away takes a rigorous, sustained contemplation of disparate pieces of evidence, a disciplined analysis of the (not immediately obvious) ways in which those strands of evidence must be related. I think Sagan omitted that piece of the puzzle to keep the narrative as simple as possible. But it is an interesting element of Eratosthenes’ work, and his grasp that the sun is so far from Earth was both an essential part of his work, and much to his credit.

LOL. Love the 'thumbnail' on this. You have given his body the configuration of an Alien Grey!

I watched this episode "live" in 7th grade science class on October 1st, 1980, when Cosmos was first released. After all these years, I still get chills at 5:00 into the video, which is the moment when Carl says, "...the surface of the Earth is curved". The best moment of the series, in my opinion.

I send this video to flat earthers regularly and I love it