so exactly how did those ancient astronomers measure with any great accuracy the 'position' of the sun at sunrise on the vernal equinox?
it cant have been easy!
Member
so exactly how did those ancient astronomers measure with any great accuracy the 'position' of the sun at sunrise on the vernal equinox?
it cant have been easy!
Order of Kilopi
With the relatively crude instruments and timekeeping of ancient times, they would have averaged the results of numerous measurements over many years. The uncertainties would average out.Originally Posted by patrick hardcore
Member
it would have to be more accurate than that to measure 1º every 70 yrs
or did they measure shifting rising positions of the stars and the vernal equinox is just used as a reference point?
Member
im really wondering exactly what the crude instruments and techniques they may have used were
Order of Kilopi
Wish I could help more but I don't have a clue.
Start here, and see where that leads you. Babylonian astronomy.
Order of Kilopi
It's not a sticky problem. Oh, wait... It is.
They'd need sticks to cast shadows and sticks to mark extremes and sticks to record notches and pairs of sticks to align to the sun at the horizon. It's halfway between winter and summer solstice. Why would that be difficult?
Established Member
Persians have celebrated Spring Equinox for literally thousands of years. Not to undermine the ancients' astronomy, but the equinoxes are the easiest thing to figure. No super sensitive observations are required. They are the only 2 days per year where the length of the day and night are the most equal. the position of the high noon is very stable close to the equinoxes.
Solstices are not too hard to figure either.
Aristotle calculated the circumference of the Earth with 98% accuracy. Now there is something many couldn't do even today. Remember there were no Wikipedias to look things up.
Order of Kilopi
The ancients had something which we don't have anymore, something very valuable, something we tend to forget and neglect to include in our reflection on the past. It was at their disposal and they used it to suit their needs: time.
The ancients had no need to extrapolate on partial data. They just waited, observed, measured; over years, decades, generations, centuries. Rinse, repeat.
This was no hobby for them. Celestial phenomena, so they believed, directly affected their very existence and understanding the skys was essential to their welfare. They took it all very seriously and knew that they had to be as precise as possible: being sloppy and doing the wrong thing at the wrong time could get a deity mad at them, causing a bum crop, drought, animal disease, whatever.
When their lives depend on it, humans can be extremely ingenious in coming up with methods to get things done.
Member
no sorry i didnt explain myself obviously
how did they measure precession of the equinoxes
it seems (as it is called the "precession of the equinoxes"
they were actually measuring that the equinox or sun position at the time of the equinox
as in a very accurate position of where the sun was in fromnt of the constellation
well if the sun is around then its too light to see what stars the sun is in front of
so they must have some special tecnique to wok out what star was there
i have heard they used something that worked out the difference between the point the stars revolve around (for us the pole star now - for them something different)
and the point the sun moves around (that spot in draco which has prob got an official name but is like the north solar pole if you get my drift)
any guesses how they did it - they noticed a 1º shift over 70 yrs - that was like 3 generations back then!
Order of Kilopi
Yup, and if it took them 60 generations to notice the cycle, then it took them 60 generations.
Their observations went on over thousands of years with the accumulated knowledge being passed down through the generations.
As I said above, they had time, and in a way that we no longer have it or understand it. What's three generations? Nothing. What's 60 generations? Not much.
As archaeology has shown, Anatolian linear pottery went totally unchanged for over ten thousand years, so what's a generation or two, or three, or ...
Order of Kilopi
You're projecting our way of life onto them. kleindoofy explained it well:
From Precession of the equinoxes/History in wiki:
EDIT: Oops! kleindoofy beat me to it.Hipparchus gave an account of his discovery in On the Displacement of the Solsticial and Equinoctial Points (described in Almagest III.1 and VII.2). He measured the ecliptic longitude of the star Spica during lunar eclipses and found that it was about 6° west of the autumnal equinox. By comparing his own measurements with those of Timocharis of Alexandria (a contemporary of Euclid who worked with Aristillus early in the 3rd century BC), he found that Spica's longitude had decreased by about 2° in about 150 years.
Last edited by PraedSt; 2008-Nov-27 at 09:49 PM. Reason: Spelling
Established Member
*- In order to observe equinox precession you will need to observe the moment of equinoxes
*- Equinox is the moment when the sun shines vertically over the equator. This happens only twice a year.
*- In order to observe the equinox you need:
**- A way of measuring the angle of the sun relative to horizon
**- To know your latitude (i.e. your locale's angle from the equator)
**- The local time (i.e. the angle of your meridian relative to the one along the sun)
These are all the information you need to figure out the angle of the incidence of the sun relative to the equator. The calculations are complex but trigonometry was invented millenniums ago.
*- Theoretically observance of just two spring equinox is sufficient to determine the duration of a year and thus being able to predict the future moments of equinoxes with good accuracy. Every year the spring equinox occurs just-under-6-hours after the last one so if you observe one in the morning, in two years you would observe one at night at the same locale.
*- Also by measuring 12 hours from the moment of daytime equinox you would know the opposite celestial direction
Established Member
Apparently now modified to mean "measure precession of the equinoxes".
What is meant by "ancient"? Are we talking Hipparchos ancient which means sometime around 140 bce or are you talking ancient as in 1500 bce or 2000 bce ancient?
Many pseudo-scientists claim the ancient peoples not only knew of precession but had somehow managed to accurately measure its period, long before Hipparchos. I personally feel this is bunk but would be happy to be proven wrong.
I say, Hipparchos was the first to measure precession and he was not all that accurate, describing a cycle which progressed at 1 degree per 100 years, an error of some 28%.
Order of Kilopi
Good question.
I was referring to Stonehenge ancient.
Banned
This is key, and it's foundation was writing. I have no doubt that brilliant and creative geniuses among men may have invented, during their lifetimes, ways of navigating the globe, thuse leading to the migration of humans all over our planet. For many years, archeologists maintained that humans only migrated across land bridges, but there are key indications, including genetic markers, which provide substantial proof that seafarers settled the Americas perhaps tens of thousands of years ago.
It wasn't until the codification of writing, however, that ancient astronomers were finally able to record their observations to compare with future observations, including those of their descendants.
While cuneiform began with the Sumerians around 3500-3000 BC, I've littled doubt that writing began much earlier, at least as early as the 7th millennium BC. These appeared on many media, as proto-writing, the ancient traditions of symbol systems, which used ideographic and mnemonic sysmbols to convey information.
Regardless, men have been drawing lines in the sand to convey various ideas since men could hold sticks in their hands. Just as military leaders would map out rivers, treelines, mountains, and depict location of troops and movements, so ancient astronomers would depict various concepts such as moon-rise and the position of the sun, moon, and key stars, as a way of determining the best time to plant.
Agriculture was developed at least 10,000 years ago, and since the beginning, ascertaining the best time to plant was critical. Ancient astronomy is closely tied with this requirement.
Member
yes i realised time was crucial when i was showing someone the path of the full moon in mid sept and said its path is (fairly) close to that of the Sun vernal equinox
over many centries it would be obvious that the mean position of the full moon nearest either equinox will be wandering 'backwards' over time
or also the position all the stars rotate around would noticably move
so im just wondering why its called the 'precession of the equinoxes'
i understand its where we mark RA=00 from
but is it just a throwback to astrology?
so now theres 3 things im curious about
1) why do astrologers have this first point of aries thing going on if it couldnt be REALLY accurately measured (haha i dont really expect anyone here to speak on behalf of astrologers) so maybe forget that one
2) when i googled it i found this guy trying to sell this book who claimed they used this device to measure it
3)would any instument or technique like this or say the timing 12 hours then measuring work to the fractions of a degree accuracy however much you didnt want to upset the gods(esses) by being careless?
Established Member
Accuracy is the key. You need accurate angular measurements and accurate time measurements.
Both would have been possible to a reasonable degree to someone with crude tools but good intelligence. The ancients could establish the horizontal plane using calm water could use a simplified sextant with or without mirrors to measure angles and setup accurate sand clocks by successive approximation.
Again, you could observe the equinoxes at night. Sun does not need to be visible. You could calculate the moment of equinox if you knew the duration of the year and the time of any respected last equinox (i.e. spring or fall).
You could also observe the equinox directly at night related to the background stars given there are no light pollutions, moon or clouds by observing Gegenschein instead of the sun. However you could not use sticks and shadows for this one.
Banned
It's because Earth is wobbling (precessing) on it's axis. Thus, the equinoxes no longer occur when the constellations are at the same point in our journey around the sun now as they used to.
Like you said, the First point of Aries is used by astologers, not astronomers.so now theres 3 things im curious about
1) why do astrologers have this first point of aries thing going on if it couldnt be REALLY accurately measured (haha i dont really expect anyone here to speak on behalf of astrologers) so maybe forget that one
I know enough of celestial navigation to derive my own measuring device using nothing more than a hunting knife and materials commonly found in any wooded area. It's not exactly rocket science... (have to fast-forward to the 1930s for real rocket science2) when i googled it i found this guy trying to sell this book who claimed they used this device to measure it.)
The wording of your question is a bit disjointed... Did you mean to say... Oh, the heck with it - say it again, please.3)would any instument or technique like this or say the timing 12 hours then measuring work to the fractions of a degree accuracy however much you didnt want to upset the gods(esses) by being careless?
In the meantime, there are simple techniques which can be used to ensure one's measurements are precise, not just to fractions of a degree, but to even hundredths of a degree. However, let's put this into perspective:
The Sun's height changes 360 deg in 24 hrs.
60 sec in a minute, 60 minutes in an hour. Thus, there are 86,400 ar-seconds in a day. Divided by 360, that's 240 arc-seconds per degree, or 0.004167 degrees per sec.
Since, for the Earth's surface, each deg = 60 nm, each min = 1 nm, and each sec = 100 feet, in order to obtain 100 ft accuracy, we'd need a timing device accurate to 1 sec with a perfect instrument, or an instrument accurate to 0.004167 degrees with a perfect timing device.
Let's say that it's feasible we could make an instrument with a diameter of 30'. To what precision would the tick marks have to be on it's perimeter to achieve an accuracy of 100'?
Using c=2*pi*r, that's 2*3.1415*15' = 94.24778 feet. Since there are 86,400 sec in 360 deg (or 94.25 ft), we find that 1 sec = 0.01309 inches, or about 1/64th of an inch.
Is that doable in real practice?
Well, no, at least not with a single 30' instrument. The point of the exercise, however, was to get a feel for the degree of accuracy required to fix one's position within 100' on the Earth, assuming they had corrections for the other errors, including refraction, precession, nutation, and elevation.
Armed with this information, it's easy to see how a larger instrument, one that was part of a structure, would have been child's play to merely determine the two days of the year when the length of day and the length of night were either equal, or were more equal than at other times.
Order of Kilopi
Not necessarily.
In our day and age of ubiquitious out-of-the-box third party remedies, we tend to underestimate the industrious ingenuity which humans can call their own when put to the test.
Until recent times when literacy had become common in many parts of the world, most craftsmen and artisans were illiterate. Their 'secrets of the trade' were passed on to apprentices eye to hand to mouth to ear. Not just blacksmiths but (musical) instrument makers, canon makers, builders, etc.
Most of this was never written down, quite to the despair of modern historians, and was known only to the trade guild members.
Since knowledge of the heavens was vital to welfare in pre- and early historic times, this knowledge was probably kept secret, know only to the chosen few (e.g. priests), since knowledge in the wrong hands can be used *against* the common good. There's always a well poisoner around somewhere. (In the Hittite society, it was forbidden for any foreigners to take part in public religious ceremonies. It was feared that they would *purposely* do something wrong, making the rituals invalid and getting the gods mad.)
There are thousands of ways of recording information without writing, and we all use some of them every day: e.g. memnotic rhymes, etc.
Order of Kilopi
Good exercise. I like practical stuff.
Order of Kilopi
Could you please repeat that in English?
Althought the poor Sumerians were misrepresented above, they did make a very valuable contribution to our everyday lives. The Sumerians used a sexagesimal counting system, which later became a mix of sexagesimal/decimal. (That means they counted in groups of six, not groups of ten, like we do.)
This is the origin of many measurements we still use today (according to contemporary historical theory):
- 12 (the dozen as a unit),
- 24 hours to a day,
- twelve months to the year,
- 360 degrees to a circle,
- etc.
Why did they use a sexagesimal counting system? We don't know.
But that might relate to your question. I'm not sure because I didn't understand it.
Banned
Perhaps that's what the gods demanded...
Seriously, it's interesting that sexigesimal system uses 60 as it's base. 60 has 12 factors: 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, and 60. This makes fractions easy.
The sumation series is: 1, 3, 6, 10, 15, 21, 31, 43, 58, 78, 108, 168.
The prime factors are simple: 2, 3, and 5.
And it's found throughout many more systems than most of us are aware! For example:
1. 360 degrees in a circle: 6 * 60.
2. 60 nm in a degree of latitude.
3. 12 months in a year.
4. 60 minutes in an hour.
5. 60 seconds in a minute.
6. 24 hours in a day (12 * 2, ie, 12 hours in a day, 12 hours in a night, during each of the two Equinoxes).
7. Since the sun transits the sky 1 deg every 4 min, that's 1 deg every 240 sec. Thus, that's 15 arc-seconds every minute. 4 * 15 = 60.
8. 240/15 = 16. A Stone in Chinese weight is equal to 160 pounds. Although there are 14 lbs in a stone, 8 stone make a hundredweight, so that's 112 lbs. 112/4=31, which is an unusual number in the summation series.
9. Original records were 78 rpm. Why 78 rpm, and not 60 rpm? Well, it's a triangular number, and it's factorization makes it a spheric number. It's a multiple of a perfect number. But that's not why... The real reason is that at 78 rpm, the hiss frequency exceeded the range of the equipment to reproduce, which allowed for some very clear sound (still a lot of pops, though). And 78 rpm was chosen because the frequency of electrical energy was 60 Hz, but a synchronous winding wasn't quite good enough, phonically. The next lock-step solution with respect to ensuring an even rpm was 78 rpm, as it's the product of 6 and 13, as well as 3 and 26, and 2 and 29. It was easy to do design the electric motor and it's windings/coils to produce an rpm of 78.
10. There are 168 primes less than 1000; our number system (thousands, millions, billions) is based on 1000. Even our engineering notation uses thousandths, thus, E3, E6, etc.
11. 15 is the magic constant of the unique order-3 normal magic square. In Biblical terms, there were 15 steps on which the Levites stood during offerings, and there are 15 chapters in Psalms collectively known as the Songs of Ascent. Because in the Hebrew numbering system the 1 and the 5 spell out one of the names of God, 15 in Hebrew is written using the 9 and the 6.
12. 15 represents the first point in a game of tennis.
13. 15, in most cultures, is the age when adulthood officially begins.
14. There are fifteen men on a dead man's chest...
15. Blackjack is 21.
In summary, and put simply, the sexagesimal system is replete throughout many cultures on our planet!
And this little gem:
"Book VIII of Plato's Republic involves an allegory of marriage centered on the number 604 = 12,960,000 and its divisors. This number has the particularly simple sexagesimal representation 1:0:0:0. Later scholars have invoked both Babylonian mathematics and music theory in an attempt to explain this passage."
Member
having reread my point3) - even to me it may as well have been in esoteric cuniform!
perhaps those very gods were directing my confusion to bring about such intriguing discussion
though i wtill want to know why it got named
"the precession of the equinoxes"
how about calling it something like
"the precession of regulus"
(i use regulus cos its right on ecliptic)
my point is - surely its easier to measure the change in rise position of a star than to measure where the sun is against the celestial sphere at sunrise of the v equinox
i know we humans can be smart, careful and devise clever tool and a few suggestions have been made as to how it could be done
am i missing something and it simply is the best way to measure precession over time or did we get stuck with it through some long lost tradition/religous pratice
Member
btw nice stuff about 60
also in base 10
360 contains 4/5 of the first 12 numbers as its factors
Banned
Although it's the Earth that precesses, in so doing, the Equinoxes retrograde with respect to the heavens.
No - it's much easier to find the one 24-hour period where the duration of day and night are closer than at any other time of year.my point is - surely its easier to measure the change in rise position of a star than to measure where the sun is against the celestial sphere at sunrise of the v equinox.
Yes, you're missing something. We got stuck with it because we need food to eat. It was critical to know the Spring equinox because that was a defining date upon which planting dates could easily be calculated.i know we humans can be smart, careful and devise clever tool and a few suggestions have been made as to how it could be done
am i missing something and it simply is the best way to measure precession over time or did we get stuck with it through some long lost tradition/religous pratice
Precession was simply an afterthought, some observation made by an overattentive astronomer.
Precession does not change the date of the equinox as it concerns the lengths of days and nights, nor it's affect on the weather.
Order of Kilopi
While correct, that's expressing it in rather a modern, secular, and enlightened manner.
The ancients didn't regard astronomical cycles as regular movements of celestial objects. To them they were the, hopefully, predictable habits of the gods. To them, occurences such as the equinox were intertwined with some mythological divine action. They waited for it, hoped, prayed it would happen, made sacrifices to soothe the gods, to influence them to 'do the right thing.' If it didn't happen, they knew they were headed for certain hardship. Enough went wrong in their lives that they couldn't depend on an absoluteness of astonomical phenomena, an absoluteness which we now know exists.
Any number of astonomical phenomena coincided with important issues, including planting, harvesting, hunting. Certainly many more phenomena than we are readily aware of today.
For us, things like eclipses, comets, etc. are trés cool. We hear about them on the news and, depending on what it is, even stay up nights to watch. To the ancients these things were not only unexpected, they were grounds for fear and horror. Something was wrong, they were going to suffer.
Exactly. But at a much later date. To the ancients it was all part of the gods' habits.
When we know about these things and read the [really] old myths, things become clearer. We usually hear about the "sun god riding his chariot across the sky." Sure, that's an easy one. But what about a god who goes on a long journey and returns every 16 years ... There are those too.
Established Member
http://www.speed-light.info/angels_speed_of_light.htm
Thats why, I come to scientific experts in astro BAUT.
I don't have the skills to prove either way.
So just a math crunch.
Order of Kilopi
I'm having a bit of trouble understanding what a link discussing the Koran, angels and the speed of light has to do with the subject of the thread. Could you explain?
I say there is an invisible elf in my backyard. How do you prove that I am wrong?
The Leif Ericson Cruiser
Order of Kilopi
That's why I send you to topic Speed of Light in the Koran??.
And then, if that's not enough, from even earlier, see topic "Quran has Speed of light"? Or, strange coincidenc.
Could we now get back to the subject of this topic?
Established Member
Sorry folks, I'm not buying any of this farmer needs the precise date of the equinox to know when to plant, stuff. First off there is certainly no proof or tradition which indicates this, and secondly what if it was cloundy that day, or that week or that month? Farmers can tell the season just by noting which plants emerge, or which plants first bud or which changes a particular color; which birds arrived; which animals emerged from hibernation possibly even the first thunderstorm after winter. A farmer likely checks a myrad of signs of which the equinox is probably not even on the list.
If there were any kinds of stellar tracking going on in neolithic times, it was probably by a priestly class who preferred eoteric knowledge to sod busting.
ETA: And I maintain my contention, that ancient people did not understand or measure precession until Hipparchos decided to look back at ancient records and put two plus two together (though they may have noticed something odd about the sun wrt the starry night.)
Last edited by Veeger; 2008-Nov-29 at 03:39 PM.
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