Tom Hanks’ character in Cast Away kept track of the motion of the sun on a cave wall. This is known as an analemma. It makes a kind of a figure-8 shape (the exact dimensions depend mostly on latitude) and the solstices are the ends of each loop.
Yes but the movie completely skipped over the amazing luck that he just happened to find a cave with a small hole in a very thin wall which projected a tiny shaft of light which would illuminate the wall right next to his bed, at noon each day. And clearly Chuck had more knowledge than the average ancient time keeper. Consider the scene where he used geometry to calculate the size of the search area he was in (in square miles) and then recalled his encyclopedic knowledge of the sizes of various US states (in square miles) in order to conclude “That’s twice the size of Texas”. Come to think of it, why didn’t he just say “That’s the size of Alaska”? But I digress.
It’s a helluva lot easier to watch shadows on the ground than it is to construct Stonehenge or search for a naturally occurring camera obscura. A good old sun dial is the obvious answer. If you want accuracy, just make the thing bigger. http://ccphysics.us/henriques/a105l/Sundial.htm
You don’t need a huge set of stones to mark astronomical time.
Many Native American groups used medicine wheels to mark the heliacal rising of stars. Just a center cairn and some ordinary stones on axes point to interesting points on the horizons. The same system would work for sunrise/sunset points but may not be as accurate. (Stars are small, the Sun is big.) The
Note that until modern times, people lived with errors. E.g., the beginning of the lunar month is important to some religions. But spotting the actual new Moon is hard sometimes. Some groups have switched to a theoretical new Moon (which may not match the actual new Moon) but some haven’t and the start of a month is “flexible”.
So, the timing of a yearly event could be viewed as “close enough” to most people.
I started a thread with a very similar question a while back. You might be interested in some of the relies there:
You don’t need anything more than your eye, arm, and hand for some of the simpler ones.
Make a fist. Stick your arm out to your side. Look at it in comparison to the sky. The fist is approximately 15 degrees, or 1 hour of sun movement on its track. Count how many fist-widths it is from the current sun position to where the sun is going to set (you do know that, don’t you? The ancients did, and some of us moderns still do). There’s your sunset time in ‘hours from now’. Anytime from mid-afternoon on, it’s good to 15 (time) minutes or better. I do that all the time when I’m out fishing in my canoe and want to know how long I have to paddle back to where I parked my car so I can still have enough light to reload and secure the boat.
It also works (although not quite as well) to tell you where the Moon will be, tomorrow, relative to the stars behind it. Tomorrow, at this time, it will be 2/3 of your fist east of where it is tonight.
Those dead, old cultures weren’t stupid. They saw these things and worked them out as easily as I did. They’re bloody obvious if all you do is look at the sky because there’s no TV or WoW. And care enough to pay attention. Their lives depended, much more than ours, on noticing that shit.
Not really. For example, the evolution of the Roman calendar (from 10 months to 12 and finally adding leap days every four year) took several hundred years and a slew of reforms in the 1st century BC. Calendars were adjusted as people learned more precise ways to measure time.
There’s got to be more to it than that. it didn’t take very long to figure out that a year was around 12x29.5 and then some, not 10x29.5 (or 10x 30 or 31) days. I assume the very first things ancient people noted were how many months in a year (roughly) and that the moons and years were not in sync.
The numbering systems were simply not formalized until later, because generally there was no need… Amateur astronomers of the day (or the priests, etc.) could say by the star positions when solstice or Passover or Yule or whatever occurred. They didn’t need to consult a calendar chipped into the wall and say “is it the Ides of March yet?”
IIRC the Romans were fairly lax until Caesar, they would just toss in the odd correction days when the calendar got out of sync. This was all well and good for a small city state. I assume by the time the empire was pushing the limits of communication, some more formal way of synchronizing the calendar was called for, instead of having an email scroll sent to every legion outpost “please add IV days to December this year”.
The correction days were outside months; originally, the months were all 30 days.
The Roman calendar is an excellent example of who little interest many ancient people had in exact timing. The later winter months weren’t worth bothering with all that much. The length of the “official” year was fooled with to lengthen/shorten a consul’s term in office. Etc.
(People still noted the spring equinox regardless of the official calendar for agricultural reasons.)
It wasn’t like they didn’t know how many days there were in a year, it just didn’t matter a lot to them. It’s like people not caring if it was 8:01am or 8:02am until quite recently.
Exactly.it was important once you were trying to run a state several hundred miles across.
More like a couple thousands, but who’s counting.
I thought one can also determine local noon by a vertical pole and rocks or something to mark the length of the shadow. The shortest shadow is noon.
You can do that, but it’s usually not the most reliable method. It’s usually easier to find the shadow at sunup and sundown and bisect that angle.
yes, I was trying to remember how big it was in Julius’ day, but the bigger it got, the more important that things were precise. Once you got to monthly leases or annual leases, interest payments, when taxes were due, etc. - it was not acceptable to be tossing in a few days here and there or have the occasional week that wasn’t part of a month etc. (Or have the government close off one year and start a new one just to mess up some politics)
I remembered that Julius was after the Punic Wars, wrote a book about his relationship with some dudes whose descendants would later build Versailles and had some chick go visit him in a rug (apparently they hadn’t invented buses yet). Check out the distance from, say, Alexandria to Lisbon.