History of Astronomy Part 2: Early Measurements of the Earth

After many centuries of pure observation, it finally became time for mankind to start doing some science to figure out the dimensions of the Earth and other nearby objects. What were these early experiments? What did they tell us? Let's take a look!

Check out "Is This Wi-Fi Organic?", my book on disarming pseudoscience!

[cgaccount]

It's kinda amazing these ancient people made accurate estimates. And amazing the history of these predictions wasn't lost. It's sad to think how many brilliant ideas were likely lost over time

[fallendown]

Even the ancient humans were capable of doing advanced science without having the option to go southern hemisphare nor the poles nor the Earth orbit. Humans are dang clever eh?

[carlatteniese]

Prof. Dave – — dude! Your explanation of Eratosthenes calculation is the best I have found so far – meaning that it is the simplest and easiest understand, almost instantaneously. If the school you work at has not awarded you by now you need to work at a different school.

[Naanthaan_Rishi]

Sir, you are ours best teacher ever seen!!

[michaelpisciarino]

Science: Observations, Explanations, Predictions, *Math*

Civilization:
Greece: Pythagoras, Aristotle,

Eratosthenes used a well, an obelisk. the sun, shadow angles, and proportions

7 degrees of the vertical
7 degrees/360 = 1/50 of the Earth's Circumference
1/50= 5, 000 Stadia/x, x being the Earth's Circumference

3:39 Other Objects
*Aristarchus*
Moons Diameter is about 1/3 of Earth's, this was off

[Essentialsend]

thank you for the great vid. One small detail: the obelisk is dark where it is hit by the sun and illuminated there the shadow should be ;-)

[binatamandal]

Brahmagupta also gave the diameter of earth.

[nikhilkapoor]

Hey Professor Dave! How did Eratosthenes manage to take simultaneous observations of the obelisk and the well given that they are far apart and that they didn't have clocks then? Were these places on the same longitude?

[theotherguy]

old video, but i'm confused at 2:50 if they were trying to measure the size of the earth how did they know how long the lines should be to be at the center of the earth? because at best they could guess how depth to the core and that would severely affect the angle

[blackmewtwo]

It’s amazing that they didn’t realize the earth was round but realized the sun and stars are I would’ve connected the dots

[Selenium]

Everyone should have a look his content

[davelambert]

Wrong. But then again, these ball theorists can’t explain no curvature at 150k feet from weather balloons.
So either, earth is flat, or much larger then they think.

[naveenkumarrv]

professor please provide the lyrics of your video intro theme song in video english caption subtitles. it's awesome

[ZoomStranger]

Many thanks Professor Dave, refreshingly informative and helpfully neutral in those rosy days before you became frustrated by the flat earth movement.

[ILikeStyx]

This is the video flat-earthers never watched :P

[andrew]

The inscription below the supposed statue of Aristarchus says “Antisthenes.” Just FYI.

[delmaticic]

Helpful lecture! But thee bust at 4:37 says "Antisthenes" not Aristarchus.

[abinr]

Thank you professor Dave I am From India... Completed mechanical Engineering this year... Do you know... Indian Educational system is too Bad... Somebody get good knowledge.. in case of CBSE students... Poor students not get same amount of knowledge...one day i will change ... I want learn more... So keep updating videos

[PunmasterSTP]

Sorry I don't quite buy it. How do spheres just exist in nature? I don't see them anywhere. But lots of things around me are flat, like my computer screen. So why wouldn't the Earth and other planets (like the moon) be flat as well?










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