The region around #MontesApenninus including #Eratosthenes & #Archimedes at 16:59UT 6th Feb '25. Taken from Oxfordshire, UK with a #WilliamOptics 70mm refractor, #Celestron 3x Barlow & #ASI120MC camera. Best 50% of 1,000 frames #LunarPhotography #LunarCraters #LunarMountains
Sun rising over #Plato, #MontesApenninus & #Eratosthenes, and #Clavius. The images were taken 2hrs 45mins apart on 6th Feb '25 from #Oxfordshire, UK with a 70mm refractor, 3x Barlow + #ASI120MC camera #LunarSunrise #CraterSunrise
#Eratosthenes says, on 11 June 1184 BC, Greeks sacked Troy by sneaking through the gates inside the Trojan Horse. Other sources say 24 April. Centuries later, French historical comic book heroes #Alix and #Enak find the wooden horse, along with a Trojan plot for revenge!
#Eratosthenes says on 11 June 1184 BC Greeks sacked #Troy by sneaking through the gates inside the #TrojanHorse. Other sources say it was 24 April 1184 BC. Trojan piñata horse cartoon by Liam Francis Walsh.
How Eratosthenes measured the earth: part 4 of 4.
The angle of the sun is the last hurdle Eratosthenes had to overcome with his data collection methods.
Here we review the popularly believed story -- measuring shadows of sticks -- before looking at a more likely and methodologically simpler alternative.
Concludes with a bibliography.
(Reading time: 15 minutes)
#ancientscience #eratosthenes #geography #ancientgreece
https://kiwihellenist.blogspot.com/2023/07/eratosthenes-4.html
How Eratosthenes measured the earth, part 3 of 4: distance.
How did Eratosthenes find out the distance from Syene to Meroë? What units did he use, and what do they mean in modern units?
(Reading time: 18 minutes)
#ancientscience #eratosthenes #geography #ancientgreece
http://kiwihellenist.blogspot.com/2023/06/eratosthenes-2b.html
The ongoing story of how Eratosthenes measured the earth, based on ancient evidence. Part 2b: distance.
How did Eratosthenes find out the distance from Syene to Meroë? What units did he use, and what do they mean in modern units? What's the difference between the 'metrological stadion' and the 'itinerary stadion'? (And how do they compare to the kilometre and the 'itinerary kilometre'?)
(Reading time: 18 minutes)
#ancientscience #eratosthenes #geography #ancientgreece
https://kiwihellenist.blogspot.com/2023/06/eratosthenes-2b.html
How Eratosthenes measured the earth: an account grounded in ancient evidence.
Part 2a explains the basic idea underlying the measurement, and begins to look at the hurdles involved in obtaining observational data.
Parts 2b and 2c will look at what we know about measuring overland distances, and 2nd century BCE instrumentation for observing the angle of the sun.
(Reading time: 16 minutes)
http://kiwihellenist.blogspot.com/2023/06/eratosthenes-2a.html
#ancientscience #eratosthenes #geography #astronomy #egypt #ancientgreece
#Eratosthenes says on 11 June 1184 BC Greeks sacked Troy by sneaking through the gates inside the Trojan Horse. Other sources say it was 24 April 1184 BC. #TrojanHorse art by #AngusMcBride.
How Eratosthenes measured the earth. Part 2a.
The ongoing story of Eratosthenes' measurement, grounded in ancient evidence.
Part 2a introduces the basic principle of the measurement; the technological hurdles involved; and how he solved the problem of simultaneous measurements.
(This was _not_ a problem to be solved with two sticks!)
(Reading time: 16 minutes)
#ancientscience #eratosthenes #geography #ancientgreece
https://kiwihellenist.blogspot.com/2023/06/eratosthenes-2a.html
Left: an ancient device for determining the azimuth of the sun at midday transit, described by Ptolemy.
First you use a gnomon aligned with the meridian to determine midday. You move the inner ring of the device until the shadow of ridge A falls on ridge B. Then you read the angle of the sun on the outer ring. Precision is to closer than 1 degree.
Right: a 2nd century BCE graffito from Meroe, Sudan, apparently depicting an astronomer using this instrument.
The length of the stadion, the ancient Greek distance unit, has had a lot of ink spilled over it.
Most of the confusion relates to conversion with Egyptian units, and selective citation. The schoinos was wilidly inconsistent. Eratosthenes' stadion works out to anywhere from 157.5 m to 262.5 m depending on how you calculate it.
When Pliny expresses Eratosthenes' stadia in terms of Roman miles, suddenly they're much more consistent with other reports.
Eratosthenes' wobbly Alexandria meridian.
In the mid-200s BCE Eratosthenes invented the device of lines of longitude and latitude. The Alexandria meridian held a central place in his account of the geography of the known world.
Key locations on the meridian: Olbia (Ukraine), Lysimacheia (Türkiye), Rhodes (Greece), Alexandria (Egypt), Syene (Egypt), Meroë (Sudan).
How Eratosthenes measured the earth. Part 1: the discovery of the earth's shape.
Before 400 BCE, everyone was a flat-earther. Afterwards, it gets hard to find people who weren't aware that the earth is round.
A look at early Greek thought on the shape of the cosmos, the earth's location, and the angle of the ecliptic, leading up to the first estimate of the earth's size in Aristotle.
(Reading time: 18 minutes)
https://kiwihellenist.blogspot.com/2023/04/eratosthenes-1.html
#ancientscience #eratosthenes #geography #ancientgreece
