Submitted by Slokkkk t3_11dm4k6 in explainlikeimfive
People used to have 365-day calendar's since thousand's of years ago. How did they know that it took 365 days for the earth to complete an orbit around the sun?
Comments
GermaneRiposte101 t1_ja9zipk wrote
And, for reasons to do with farming (planting crops/harvesting/etc) there was a very real need to learn this.
People were not stupid in olden times: they just had less knowledge.
whereisfatherjack t1_jaa0257 wrote
Less technology
thatthatguy t1_jab9pmu wrote
They knew what was relevant to them. More personal experience kind of knowledge than book larnin’. When your livelihood depends on finding edible plants and tracking animals to hunt you het pretty good at recognizing patterns in the weather and seasons. I might be able to say that there are just under 365.25 days in a solar year. A hunter gatherer will know that when the rains stop you have only a few days to move camp to where the herd likes to come through. But harvest as many of the funny blue berries as you can before you leave because they’ll be gone before you come back.
whereisfatherjack t1_jac04y3 wrote
They recorded and taught book-smarts verbally, through poems and songs
TucsonTacos t1_jaan0o8 wrote
Well both
Edit to say: My bow!
syds t1_jabcfub wrote
and my axe!
panjialang t1_jaboaqt wrote
Dude fuckin nice
Smallpaul t1_jabrm0f wrote
Both. They had neither the content of Wikipedia nor the technology to store it.
whereisfatherjack t1_jac01n1 wrote
They had a lot of the content and they stored it verbally, through songs and poems.
Smallpaul t1_jact4ov wrote
They had a tiny fraction of the content. They didn’t know what an atom was, not a galaxy, nor a continent, a complex number, etc.
They may have had wisdom about how to run their societies, live a good life and live in their local environment, but that is not the same as having vast global knowledge.
darklegion412 t1_jaaflwp wrote
>you'll quickly realize that it changes on a predictable ~365-day loop.
Quickly, being relative here.
RighteouslyNeutral t1_jabpbtz wrote
It wasn't even always that complicated, it is easy to observe the seasons. You always know what season it is because you know what the last season was. You are going to know winter is on its way just based on however many years you have observed it. It wouldn't be like people who didn't keep track of years wouldn't know to prepare for winter. Then you have things like the zodiac, where they simply observed where the sun was in relation to the stars behind it and drew significance with what that might have meant based on the season and significant climate or weather events and so on.
Successful_Box_1007 t1_jaayq46 wrote
Cool AF! Didn’t know that they were able to track and measure they solar altitude! How did they do this with their rudimentary tools?
redvillafranco t1_jab7ala wrote
You can just look at where on the horizon the sun rises/sets every day. On the first day of summer, the sun rises the furthest north in the northern hemisphere. So you just count the days until it rises that far in the north again.
Also, you can measure the highest point of the sun in the sky each day. If you have the same length stick or rock on the ground. On the first day of summer, at high noon, the shadow will be its shortest length of the whole year. So you can just count the days until the shadow is that short again.
Successful_Box_1007 t1_jab7kef wrote
And the ancients just assumed this meant that the earth had made a full rotation (or in their eyes, the sun had)? I mean why did they settle on that assumption? I am sure one could have made a dozen others.
yogert909 t1_jab8ny7 wrote
They didn’t necessarily care about the rotation of the earth. They cared about how long until they should plant their crops again.
redvillafranco t1_jab8rba wrote
They knew that a cycle of 365 days had passed. And this period of time was extremely consistent and repeatable. And they called that cycle a “year”. But they didn’t necessarily need to know what was causing the cycle.
AliMcGraw t1_jabaz04 wrote
There was a NOVA episode just a few weeks ago that demonstrated exactly how people could do this with very simple tools! (Like, stick in the ground simple.)
The records they were sharing and recreating were from the last 1,000 years, but it's not appreciably different from what Eratosthenes did, and what we assume older calendar-making societies did. And they demonstrated so beautifully exactly how it works, A+++ go watch the show and then plant your own stick in the ground to measure sun things!
PlanetLandon t1_jabiddd wrote
It doesn’t really take anything special. If you have eyes and something to write with you can keep track of where the sun rises every day.
Successful_Box_1007 t1_jabk5wa wrote
True but isn’ the variation super small all things being equal (including time of day you measure)? With their rudimentary tools it must have been tough.
TheSkiGeek t1_jabknby wrote
Yeah, but you only need to get close. It’s okay if you’re off by a day or two if all you’re using it for is to decide when to plant and harvest crops.
If you’re staying in one place for a while you can set up more permanent solutions. Structures like Stonehenge have notches and openings that line up with the sun position in different seasons, so you can tell exactly which day is the solstice or equinox (or whatever days are important to you).
Successful_Box_1007 t1_jabl4ew wrote
I see. Thanks!
p_m_a_t_t t1_jabkoi0 wrote
Just because a tool is 'rudimentary' doesn't mean it doesn't work!
Mr_Mojo_Risin_83 t1_jabucot wrote
remember, there was no telly or movies or anything at this time. this sort of knowledge would have been carried by everyone in the tribe. this is the sort of thing they could have devoted time to every single day.
P0L1Z1STENS0HN t1_jabzoq1 wrote
A_Meal_of_Pain t1_jackbxl wrote
And the tools necessary to make these measurements are very simple. Literally all you need is a stick in the ground and a few pebbles or something else to mark the longest shadow the stick casts each day.
fiatfighter t1_jaatflc wrote
Not very ELI5 my friend.
jet-setting t1_jabl0z5 wrote
Put stick in ground. Look at shadow.
Anarchaeologist t1_ja9j59e wrote
Pick a spot and watch the sun rise. Now put a post in the ground in between the spot you are standing and the point on the horizon the sun rose above.
Now stand on that spot day after day (some days will be too cloudy to see the sun, but keep it up and you'll see a trend.) At first, depending on the season and the hemisphere you're in, you'll see the point on the horizon the sun's rising above move in one direction. But one day it will reverse. Put a post between your standing spot and the farthest in that direction the sun rose above the horizon. This may take a few years to see because of cloudy days, but eventually you'll have it nailed down.
This extreme is called the solstice. There are two of them in a year, and they mark the start of summer or winter. They have either the shortest or longest period of daylight depending on the season.
Now watch for about 6 months more from your spot, and you'll find another extreme point on the other side of your first post. This is the other solstice. Put a post there.
You'll find that it takes 365 sunrises to make the complete cycle through both solstices.
Lower_Departure_8485 t1_ja9s7a6 wrote
There's a mound builder site near Saint Louis where they used that exact method. There is a central observation point then posts laid in circles around it. Some of the posts align perfectly with the solstices others with planting times.
Even without the sticks in the ground most people who spend a lot of time outdoors would notice the pattern of the sun shifting across the sky and daylight changes.
Nwcray t1_ja9xpcf wrote
Cahokia. It’s one hell of an interesting place. I used to go on elementary school field trips every year, so didn’t realize how special it was until I went back as an adult. But wow, it’s a cool place.
IrishFlukey t1_ja9gw77 wrote
They did not know Earth orbited the Sun, thinking it was the other way around. They could determine the pattern of the seasons, with very simple signs. Thousands of years ago people could do that. They even built things to take advantage of these patterns. Newgrange in Ireland is a megalithic tomb that has a small gap above the entrance that allows the Sun to shine right through and light up inside it on only the 21st of December, the shortest day of the year. There are many other examples.
intrinsicrice t1_ja9iyd9 wrote
How could they determine that the 21st of december is the shortest day? Luck?
Without any research, I guess that it can’t be more than a couple of minutes shorter compared to the 20 and 22 december?
DressCritical t1_ja9npti wrote
They didn't, not always. Many cultures celebrated, not the solstice, but the day when they could tell that the day was getting longer and thus someday summer would return again.
The solstice wasn't necessarily the shortest day of the year (though it is). To these people, it was the day when the Sun at noon was lowest in the sky. That it was definitely the shortest day seemed likely given what else they knew, but they often could not measure the length of the day.
Measuring the comparative height of the Sun in the sky, however, takes a stick, the ground, something that can mark the ground, and some patience.
KarmaticIrony t1_ja9ngu2 wrote
They didn't pick December 21st, they did the inverse in a way. The people who built it didn't use a calendar with December as a month if they had any sort of calendar at all.
What they did was use their knowledge of how daylight changes seasonally each year, which is something they could observe, to ensure that the sun would illuminate a chamber specifically during the Winter Solstice, which happens to be December 21st on our calendar.
IrishFlukey t1_ja9jfim wrote
Simple things like lengths of shadows. The same kinds of simple things that we can do now.
annomandaris t1_jaantsm wrote
put a stick in the ground, at noon on each day, measure the shadow, the higher the sun is in the sky, the closer to the stick the shadow will be. On the day the shadow is the farthest from the stick, that means the sun is the lowest in the sky, and that's the shortest day.
TheSkiGeek t1_jabkzg4 wrote
Hard to tell when it’s exactly noon.
More reliable to mark where on the horizon the sun sets/rises each day. When the movement of that point stops and reverses, that’s either the winter or summer solstice.
DarkAlman t1_ja9oljh wrote
Ancient peoples mapped the sky. Being able to track the movement of constellations across the sky, and the height the sun would reach were key markers of when to plant, when to harvest, when the rains would come, etc in times before watches and calendars.
Going back further cavemen would use the stars to know when animal herds would return and when spring was upon them etc.
Constellations were an easy way for them to remember groups of stars, and oral traditions were used to pass stories of said constellations and that knowledge to the next generation.
So long as you figure out that the Sun rises to different heights during the year, you can figure out that the Sun reaches it's height on the Solstice, then you can count the number of days till that happens again.
The reason there's 360 degrees in a circle is because the Babylonians used circles to track the sun year round and assumed (incorrectly) that there were 360 days in a year because it was a nice round number.
It took centuries for people to realize that calendars were faulty and corrected them by adding extra days.
annomandaris t1_jaapimo wrote
Long before calendars, farmers knew the lunar schedule of 13 months of 28 days which is 364 days, and they knew it was off so every few years you had to adjust it. This would have been relatively common knowledge around 10-20K years ago.
Babylonians knew 360 was off when they made their calendar, but they didn't care. 360 was just too perfect for dividing stuff. So they just had a 4-5 day holiday after the harvest that didn't go on a calendar. People got a vacation after all that work, and the rest of the year you could divide days in your head. everyone wins.
AliMcGraw t1_jabc0b8 wrote
Lunar months are actually about 29 1/2 days; most ancient lunar calendars that don't correct for the sun use 12 months and come out with 354 days ... which is why Ramadan moves back 11 days every year (purely lunar calendar).
Most ancient calendars do correct for the sun. :) They stick in bonus days in various ways -- whole bonus month every couple years, bonus week somewhere, etc.
jaa101 t1_jab6ayb wrote
> the lunar schedule of 13 months of 28 days which is 364 days
Except that synodic months actually last 30 days, not 28, and there are nearer 12 of them per year than 13.
cavalier78 t1_ja9qs1h wrote
It's easy to figure out the rough length of the year. You can count, and you know roughly when it gets cold, and roughly when it gets hot. You notice that the Moon goes through phases, about once every 30 days. And hey, after about 12 cycles of the Moon, it goes from hot to cold and then back to hot. So how did they figure out exactly 365 days?
Let's say you build a house. You can walk outside and look at your cool house, and you notice that the sun casts a shadow on the ground. The top of your roof makes a shadow that goes right there. You're an inquisitive kind of guy. So let's say that you kind of keep an eye on how far out that shadow goes into your yard. Some days when it's too hot to do anything, you can just watch the shadow move across the grass.
So then, being the inquisitive kind of guy that you are, you notice that depending on the time of year, the shadow reaches a different part of your yard. It doesn't always go out as far. So one day you go out when the shadow is at its maximum distance, and you go poke a stick in the ground. You mark the farthest point that the shadow reached that day. The next day, the shadow doesn't reach quite as far. Almost, but not exactly.
Keep in mind that if you're lucky, you might not even have to poke a stick in the ground. Maybe on the day of the year when the shadow is at its very longest, it just happens to touch the base of a tree, or your fence line, or your barn.
So anyway, you just start counting the days until it touches that stick again. On the longest shadow day of the year, you find that it's 365 days from when it touches that stick, to the next day the shadow touches the stick. And that repeats, basically every single year.
annomandaris t1_jaapsi0 wrote
Just by watching the moon you can come up with 13 months of 28 day cycles, and that's 364 days. that would be a good enough calendar for much of human history.
The_camperdave t1_jab8xmg wrote
> Just by watching the moon you can come up with 13 months of 28 day cycles, and that's 364 days.
Um... The lunar cycle is 29.3 days long.
amazingmikeyc t1_ja9iod6 wrote
It's the same every year. The seasons change, the day length changes... They just counted the number of days until the cycle started again. Then they remembered with their Minds.
jowie7979 t1_ja9j4de wrote
People in ancient times used observation of the moon's cycles and the sun's position to estimate the length of a year. However, it wasn't until the development of sophisticated astronomical observations that the length of a year could be determined accurately, leading to the Gregorian calendar with a year length of 365 days and a leap year of 366 days every four years.
furrykef t1_jab9rvo wrote
A year of 365 days plus a leap day every four years is actually the Julian calendar. The Gregorian calendar adds an extra rule: there is no leap day on years divisible by 100 unless it's also divisible by 400.
DressCritical t1_ja9o0yb wrote
You can measure the length of the year to within the correct number of days with a stick, the ground, a way to mark the ground, the ability to count, and patience. It does not take anything sophisticated.
incizion t1_ja9pff5 wrote
>and patience
you lost me
DressCritical t1_ja9thlm wrote
Patience is required for two things.
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You must check repeatedly during the shortest days of the year to find out on which one the shadow of the stick is the the longest at noon.
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You must keep track day after day for a year until the shortest day returns again. Until the shortest days return, however, all you need to do is to add a day to your tally.
icelandichorsey t1_ja9ph4l wrote
Except the time to do and the means to do it and have the patience and the scientific method which is not actually that old.
DressCritical t1_jaa8p1a wrote
Wanna bet?
Karahan Tepe, Turkey, the oldest known ancient site accurately aligned to the winter solstice is over 11,000 years old.
There is a site in Aberdeenshire, Scotland, with a lunar calendar that used the solstice to keep on track that is about 10,000 years old, though it is not nearly so sophisticated.
There are a number of sites in Great Britain, Mesopotamia, and at least one in Germany aligned with the solstice which are as old or older than the pyramids.
The ancient Egyptians tracked more than 4,000 astronomical events. There are a number of examples of ancient calendars and structures that were aligned with the solstice created by the Egyptians, such as the Sphinx.
Heard of Stonehenge? Tracked quite a bit more than the winter solstice. Not that old considering it appears to be 7,000 years younger than the oldest known example.
If going by technology rather than age, then in the New World, we have Machu Picchu, Chichen Itza, Chaco Canyon, and quite a few others.
Scientific method? Not required. Not even close. Not even Neolithic. Mesolithic. Some of these structures were built prior to the most recent period of the Stone Age.
icelandichorsey t1_jabmyvt wrote
Fair enough, thanks
Your original comment sounded like taking our current world (or even the world of the last 500 years) for granted. A world where enough people have the time to sit around and measure things like this and make accurate enough conclusions and then also be able to influence the hierarchy enough to make it into a "calendar".
Also they would have had to stay in one place rather than migrate long enough, again, we're talking this for granted. That's no small thing although I didn't consider organised religion who of course tick all of these boxes and have been around for thousands of years.
Anyway, your subsequent response clarified that you weren't thinking like this. Thanks
annomandaris t1_jaarnci wrote
lol, you don't need the scientific method to count 13 lunar months, 28 days, 364 days in a year. and then after a few years you would realize that your days are off a little. After a few resets, it wouldn't be hard to realize that 1 day every 4 years keeps it on track.
This would have been known and kept track of so long ago, 50K? maybe 100K years ago. They didn't have writing tools but they had pretty sophisticated markings on sticks and stuff.
AliMcGraw t1_jabbit3 wrote
Also deadass giveaway that someone is a man who doesn't know much about women and generally lacks curiosity about the world when it doesn't occur to them that a lunar cycle would be of INTENSE INTEREST and OBVIOUS USE to the 50% of humans who menstruate on roughly a lunar cycle.
"Well, I don't need to know the lunar cycle, so I don't see why ANYONE would," u/icelandichorsey harrumpfs to himself, before explaining to the woman unfortunate enough to sit next to him on public transit how science works, actually.
im_the_real_dad t1_jaciaaf wrote
So you're saying that the lunar cycle appears to be 23 days long to some women and it appears to be 33 days long to other women and to still other women the moon goes through the lunar cycle in some number of days in between?
icelandichorsey t1_jabmwj2 wrote
I'm sorry, what the actual fuck? How did you get there from my 2 lines about the scientific method? You know literally nothing abjht me. Projecting much?
Erablian t1_jabcrc5 wrote
The synodic month averages 29.53 days, quite a bit different from your 28-day month. After 13 of those, your calendar would be 9.6 days out of sync with the actual phase of the moon.
13 synodic months is about 384 days, not 364.
annomandaris t1_jaar5mo wrote
>However, it wasn't until the development of sophisticated astronomical observations that the length of a year could be determined accurately, leading to the Gregorian calendar with a year length of 365 days and a leap year of 366 days every four years
people in the Stone age would have had a lunar calendar which was 13 months of 28 days, totaling 364, and they would have realized it was offset every few years and adjusted it accordingly.
This would have been known a LONG, LONG time ago, long before writing, maybe as much as 100,000 years ago
I mean Stonehenge was made around 5000 years ago near the end of the stone age, and that was a masterpiece showing knowledge of leap days and such, and this was before any of the more advanced techniques of the bronze age like water clocks, hour glasses, and more precise sundials that showed up around 3500BC.
foolishle t1_jabqt1g wrote
The lunar month is a little over 29 days so a 13 month count is going to get out of sync with the moon phase super fast.
icelandichorsey t1_ja9pcdq wrote
Before the calendar we use today people had a calendar that had. Months in line with the moon. They noticed that things repeated themselves roughly after 12 of them, so you had years with 12 months and sometimes 13. The Jewish calendar still has this.
Also isn't this fairly easy to look up on wiki?
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hocuspocus9538 t1_jaa487d wrote
I always assumed that they didn’t because they didnt think the earth orbited the sun. But the length of time of each season was predictable and so maybe that’s how time was tracked especially for people who could read and weren’t taught how to use a calendar.
annomandaris t1_jaas757 wrote
Humans had a lunar calendar of 13 months, 28 days, that would have been known soon after modern humans showed up, maybe 80-100K years ago. You need to know if you have 1 month, or 10 before the next snow comes.
That would have nothing to do with orbital mechanics or anything, even if you think apollo is riding thru the sky on his chariot, he's doing it in a predictable pattern, and recognizing patterns is basically a super power for humans, it wouldnt take long for them to keep track of it.
ZacQuicksilver t1_jaabhtu wrote
It's worth noting here that the modern 365-day calendar is somewhat recent.
Many older cultures - notably, both the Jews and Chinese, who retain their older calendars - were what are called "Lunisolar" calendars. In these calendars, you have a set cycle of months, and introduce a leap month into the calendar if a specific month would happen before some yearly event. While I can't find that for the Chinese Calendar right now, the Hebrew calendar is normally 354 days, but adds a 13th leap month if the new year would start before the Spring Equinox.
Other people have already described how these people determined the solstices; and the equinoxes are pretty easy to figure out as well (halfway between the solstices - both in terms of time; and in terms of where the sun rises/sets).
merlin401 t1_jab2dly wrote
Yeah very surprised at all the top comments explaining how the ancients had it all figured out! Even at the end of the Roman Republic they had the seasons and the calendars all out of synch until the Julian Calender figured out how to have it work out with leap years and such. And of course even that wasn’t quite right… getting a working calendar was absolutely not a trivial task (and figuring out why it worked wasn’t trivial either!)
ZacQuicksilver t1_jab6myo wrote
Except that while it's very hard to get it exactly right, it's really easy to get close.
Getting to 360ish days is relatively trivial - as best as we can tell, a 12-month, 360 (+- 10) day year was developed independently in at least India, China, Mesopotamia, and Mesoamerica - and that's a minimum: there's reason to believe that northern Europe, Mediterranean Europe and/or North Africa, Southeast Asia/Polynesia, South America, North America, and southern Africa also independently developed calendars that were not far off from 360 days. From a 360-day calendar, all you have to do is throw in a few non-year Holy Days before New Year (which, for many calendars, happens at one of the four main days - the solstices and equinoxes) until it's the right time, and move on. Alternatively, if your calendar is lunisolar, you add a month if New Year is too early.
Yes, getting things exact is really hard - even the Julian Calendar is off by a little bit, and technically the Gregorian Calendar is off by a little bit (it's off by .0003 days per year - or about one day in 3000 years). But I think you're selling human intelligence short saying it's not trivial to get a working calendar - as long as you understand the calendar isn't perfect, being a few days off isn't a problem. And both ancient calendars still in use (Chinese, Hebrew) understood that, and had rules to make sure that the calendar was not off by more than one month - and it's safe to assume they weren't the only ones like that.
Budson420 t1_jaac4km wrote
Just like the kid in the little Caesar’s commercial, they looked to the stars for the answers
Harbinger2001 t1_jab22h7 wrote
Astronomy is very ancient. Certainly older than civilization itself. They didn’t know anything about the Earth orbiting the sun, but they did notice a cycle of the sun tracing a lower to higher path in the sky over the course of a year. It is trivial to set up a line of stones to mark when the sun rises at its lowest and highest points and that gives a way to detect the winter and summer solstices.
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specialsymbol t1_jabglf3 wrote
They would poke a stick in the ground and trace the shadow at noon. When the shadow reaches a point that was already marked a year has passed.
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oudeicrat t1_jabjdmv wrote
in addition to all the great comments here about the solar latitude I'd add that it doesn't take that much technology and knowledge to count each day/night cycle and realise the seasons and the star constellations (especially the zodiac) come back and repeat after you counted roughly 365
Doraellen t1_jabqis3 wrote
If you live in the same place for one entire year, you will notice that the sun rises and sets in a slightly different place each day, eventually returning to about the same place it started. I notice this in my own house, because the window from which I can best see the sunset changes through the year! Agriculture, which allowed people to stay in one spot for extended periods of time, made it easier for humans to notice these changes relative to their fixed surroundings.
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Translated_Simple t1_jabse34 wrote
They would have used the world around them not, Use the light on a sun dial for time, Use Harvest of certain Vegetables/Fruits for season And lastly calculate all these things with their fingers and would have wound up with 2 seasons and 2 phases between them.
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Hawkishhoncho t1_jacd1d3 wrote
If you just have a post, and mark how long it’s shadow is at noon every day(aka when it’s shortest each day) and you’re any distance at all from the equator, you’ll get a 365 day cycle of that length getting longer and shorter. Or you have a water clock made of a barrel with a leak, and time how long the days are, that’ll also give you that 365 day cycle, of days getting longer until they hit a maximum, then shorter until they hit a minimum, then longer until they hit that same maximum.
QueenofLeftovers t1_jacdfi9 wrote
I would also like to add while 365 days is a super accurate number to measure, 13 full moons (or 28-day months) wouldn't be a wild stretch for smallfolk woth no education to recognise a certain season has come around again with some reliability
wilbur111 t1_jadoil9 wrote
You take the longest day of the year (the summer solstice) and then count the days until the next longest day. You then find it's consistently 365 days.
If you live in a cloudy place, this might seem difficult and inaccurate. If you lived in Egypt, you'd have lots of cloudless days to base it on.
Ohwja t1_ja9fzvc wrote
They didn't. They just got up when the sun came out, and stop work when its too dark.
In winter there wasn't anything on the land, still they did other jobs.
Emyrssentry t1_ja9i0et wrote
That's patently false. The Egyptians were able to create a 365 day cycle completely independently from any winter/summer cycle. A 360 day year, with 5 extra days added between the years.
speculatrix t1_ja9j42v wrote
AIUI, It offended the Babylonians that there wasn't an exact 360 day year, as they used base 12
Ansuz07 t1_ja9fxsq wrote
Solar altitude: the angle of the sun relative to the Earth's horizon, measured in degrees. This changes over the course of the year, with altitude at its highest in the summer and lowest in the winter.
Once you are capable of measuring solar altitude (which isn't that difficult) you can track it every day. If you do that, you'll quickly realize that it changes on a predictable ~365-day loop.