If they knew the earth rotated, then they could assume that noon happened at different times at different locations. But did they have a way to prove this without being able to travel or communicate fast enough to observe the effects?
In: Mathematics
Up until the late 19th century, all time was local. The idea that it could be a different time 100 or 1,000 miles away had almost nothing to do with the day to day lives of anyone. It was only the arrival of relatively high-speed, long-distance travel that had to be coordinated that led to the development of the concept of time zones.
I don’t know if anyone would be able to pull up a document of ancient Greeks discussing time zones.
But they all knew that noon determined your latitude and that longitude depending on WHEN noon happened but they had no accurate clocks to measure the difference as they moved distances.
I guess you are thinking that time zones can only be proven with an experiment but they did not have any technology to measure time effectively.
They tried around 300 BC to key it to a lunar eclipse, to measure the distances, but the clocks accuracy wouldn’t last long enough.
But the concept of time zones (the sun is at different points in the sky when you are at different points on the globe) is a trivial one that comes from the precepts that the earth is a globe and rotates.
So I would say they implicitly knew of them. But it didn’t matter that much? no instantaneous communication would be possible. And even fast movement and communication wouldn’t be affected by different time zones in a noticeable way.
Ancient people? Probably not. In order to measure it, you’d need a clock in order to do so, and the first mechanical clock wouldn’t be invented until the 13th century.
However, the Earth was shown to be round by Eratosthenes around 200 BC because he heard about the Sun casting perfectly vertical shadows on a specific day of the year. On the same day, Eratosthenes in Syene (now called Aswan) measured the angle of a shadow, and got a shadow at a 7° angle. He then measured the distance between Alexandria and Syene, and determined that would be 7° of the circumference of the Earth, and then calculated the whole circumference.
It is reasonable that someone could make that conclusion that something similar happens when you travel East to West, rather than North to South, but again, you couldn’t calculate thay change without transporting the mechanical clock a very long distance.
They were likely aware of the concept but would not have been able to prove it definitively. That’s where the true rub of the question is. As a similar point, it was KNOWN the Earth was round well before the age of exploration, but it was not PROVEN until Magellan’s fleet circumnavigated the globe.
Not exactly. Time zones as we know them today are more or less an invention of the railroads. The ancients understood that noon could happen in different places at different times, according to longitude. But when it simply wasn’t possible to travel any faster than 20mph or so, it didn’t really matter. People just didn’t feel a need to keep time to that degree of precision, except in some very niche cases (like when Eratosthenes calculated the circumference of the Earth).
Ancient people had an inkling about time differences, but “time zones” as we know them? That’s a bit of a stretch.
The concept of the Earth rotating wasn’t widely accepted until much later, so the idea of synchronized time zones wasn’t really on their radar. However, they weren’t completely oblivious to the fact that the sun’s position changed depending on location.
Travelers and traders noticed that the sun’s position varied as they moved east or west. Sundials in different places showed different times. But this was more of an “huh, interesting” observation rather than a codified system.
Eratosthenes, a Greek mathematician, came close when he calculated the Earth’s circumference by measuring shadows in different cities during the summer solstice. But he wasn’t thinking about time zones specifically.
Proving it definitively? That was beyond their technological capabilities. You’d need near-instantaneous communication across vast distances to demonstrate it conclusively.
It wasn’t until the advent of long-distance, rapid communication (think telegraphs in the 19th century) that we could actually prove and implement the concept of standardized time zones.
So, did they know? Sort of. Could they prove it? Not really. They had observations that hinted at it, but lacked the means to confirm or standardize it in any meaningful way.
Around 200 BC(E), Eratosthanes discovered that the Earth was round and measured its circumference after learning that the sun gave different angles to shadows in different places at the same times on the same days.
He, and anyone with his dataset and even a modest proportion of his skillset, could definitely figure out that the Sun is over a different place in the sky depending where you are on Earth at the same time, so they could figure out that when it is midnight here it must mean that it is noon on the other side of the world.
From WikiPedia page on Eratosthanes:
>In his three-volume work Geography (Greek: Geographika), [ERATOSTHANES] described and mapped his entire known world, even dividing the Earth into five climate zones: two freezing zones around the poles, two temperate zones, and a zone encompassing the equator and the tropics.
>This book is the first recorded instance of many terms still in use today, including the name of the discipline geography.
>He placed grids of overlapping lines over the surface of the Earth.
>He used parallels and meridians to link together every place in the world.
>It was now possible to estimate one’s distance from remote locations with this network over the surface of the Earth.
There is no need to physically prove it because of the reason you gave. They didn’t ” assume that noon happened at different times at different locations.” they knew that noon happened at different times. Of course by ‘ancient people’ it would only be a select few I would imagine. As in Greeks, Romans, Chinese, not sure who else. An interesting question though would be COULD they physically prove it?
For most of history, the local time is what the sundial said. There wasn’t much of a need for standard times because news took days to travel long distances. Nothing that went between towns was being measured to the hour or minute. It changed when trains were able to cover long distances in a few hours to a day. Standard times were established to help manage traffic on the tracks.
The understood the earth was round and that different points had different amounts of light
So I’d guess they understand that if it’s noon for them it isn’t noon for everyone but they wouldn’t call it a timezone, they generally just used general term times of dusk dawn noon for most things so time would be more a gradual shift then a hard hour zone
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