How did ancient astronomers track changes in positions of stars?

[syfry]

TL;DR Summary

They'd notice changes in position from shifts in Earth's spin axis, and more. To notice such details by eyeballing the positions and by timekeeping in the darkness under starlight seems like an extraordinary feat.

They might've used water clocks under candlelight to track time by dripping to marked levels of water. They might've used star dials (like sun dials but in the dark). They might've stuck objects into the ground that stick up and align with stars so they'd notice changes in position. But I didn't find any info on the internet about such things that ancient astronomers used to track motions of stars and related timing.

 

[Steve4Physics]

But I didn't find any info on the internet about such things that ancient astronomers used to track motions of stars and related timing.

Astrolobes have been around for 2000+ years so are probably part of the answer.

 

[Baluncore]

Without optical instruments, the "fixed" stars would appear fixed through the lifetime of the observer. The shape of the constellations were recognised and learned by each observer. I have not seen any evidence that the relative movement of the fixed stars was noticed.

The position of the Sun against the constellations marked the seasons of the year. The Moon provided a more accurate monthly calendar. Planets wander against the background constellations of the fixed stars. Comets run interference, to confuse the observers.

The fascinating apparent movements of the Sun, Moon, and planets, effectively distract from trying to measure minor changes in the position of the assumed "fixed stars".

 

[Vanadium 50]

What research have you done on your own? (He asks, fully expecting the usual syfry answer of "I asked you.") The Wikipedia article is pretty clear - did you look at it? If so, what part of it didn't you understand?

 

[syfry]

I have not seen any evidence that the relative movement of the fixed stars was noticed.

An article in Britannica and another in Wikipedia had led me to the conclusion.

From Wikipedia:

"Earth's precession was historically called the precession of the equinoxes, because the equinoxes moved westward along the ecliptic relative to the fixed stars, opposite to the yearly motion of the Sun along the ecliptic. Historically,[3] the discovery of the precession of the equinoxes is usually attributed in the West to the 2nd-century-BC astronomer Hipparchus. With improvements in the ability to calculate the gravitational force between planets during the first half of the nineteenth century, it was recognized that the ecliptic itself moved slightly, which was named planetary precession, as early as 1863, while the dominant component was named lunisolar precession.[4] Their combination was named general precession, instead of precession of the equinoxes."

And from the cited source:

"Around 130 BC a greek astronomer named Hipparchus estimated the length of the cycle of Earth's precession by comparing his own observations to those recorded by Babylonian and Chaldean astronomers in the preceding centuries."

Wikipedia mentions the fixed stars.

What research have you done on your own? (He asks, fully expecting the usual syfry answer of "I asked you.") The Wikipedia article is pretty clear - did you look at it? If so, what part of it didn't you understand?

What are you implying? Why should we trust that you've read the question without skipping details? You're free to contribute or to not.

 

[Vanadium 50]

What are you implying?

I am implying that you have a history of not doing a lick of work yourself, and expect us to do it for you. It's not only disrespectful of other people's time, it's disrespectful of your own.

Now, you have clarified things, you are NOT talking about the diurnal motion of the stars, nor are you talking about the proper motion of the stars. You are talking about the precession of the equinoxes. Be thankful it only took us a half dozen messages to find this out. You're welcome.

The article you cite points out that the writings of Hipparchus are lost. So expecting PF to be able to tell you what they say is unrealistic. They describe the techniques used by Ptolemy. Those measurements make it fairly clear that they are based on angular separation which requires nothing more complex than a protractor.

If there is something specific you didn't understand in that article, please tell us what it is.

 

[berkeman]

I hear the background theme music starting to rise in volume in this thread... I wonder what will happen next?

https://www.oscars.org/collection-highlights/jaws

 

[syfry]

I am implying that you have a history of not doing a lick of work yourself, and expect us to do it for you.

Citation please.

Thanks for replying.

I had problems finding out how they tracked that stars had slightly moved from their position. The rest of your comment sounds like assumptions.

 

[Hornbein]

It is my belief that the ancient Egyptians knew about the precession of the equinox. They carefully measured where on the horizon various stars rose and set. The locations of the pyramids show how accurate their measurements were. They collected thousands of years of data, which made the precession obvious.

This however was done by a secretive priesthood. They failed to publish and hence perished.

 

[Vanadium 50]

the rest of your comment sounds like assumptions.

What assumptions? That Hipparchus' writings are lost? That Ptolemy measured angles?

The exact instruments are not known. It is known that there were protractor-like objects (technically a goiniometer, which is a measuring device - a protractor is technically a drawing device) in 600 BC if not before. Astrolabes came into use about the time of Hipparchus and Ptolemy, so it is quite likely they had them. Sextants wouldn't be invented for a millennium and a half, but they might have had their predecessor, called a quadrant.

Ptolemy described his technique more than his instruments. I'm sorry if you want more, but that's what he did.

 

[Baluncore]

So this thread has nothing to do with the movement of the fixed stars, and everything to do with the precession of the equinoxes, against the background of the fixed stars.
Should this thread title be:
"How did ancient astronomers identify the Precession of the Equinoxes".

Observations of the azimuth of sunrise and sunset reveal the seasons and the Earth year.

Observations of the position of the Sun, against the constellations of the zodiac, also revealed an Earth year.

But those two independent annual calendars drifted very slowly against each other, which, once noticed over several centuries, revealed the precession of the equinoxes.

 

[syfry]

So this thread has nothing to do with the movement of the fixed stars, and everything to do with the precession of the equinoxes, against the background of the fixed stars.
Should this thread title be:
"How did ancient astronomers identify the Precession of the Equinoxes".

Thanks for pointing that out.

Does that mean they did or didn't notice the stars move? (with such slow changes from the 26,000 year cycle of axial precession)

For me personally, and possibly for many more people than you might suspect, my reading comprehension plummets for technically worded writings.

Wouldn't expect you to understand as it's perhaps (understandably) beyond your personal experience.

But I voice it to help inspire people who can relate and who might dread to voice their experience in what they might perceive as an unwelcoming atmosphere to voice it.

Rereading a topic and searching for multiple places that rephrased it various ways and searching for visual demos does help in many cases, but there are also many instances where I can spend months and years revisiting a topic and it's merely spinning wheels getting nowhere, or gaining a mistaken sense of understanding only to find out it's an utterly incorrect misunderstanding of the topic.

For certain cases, realization is possible only if someone spells it out (in the right way). No amount of personal review gets anywhere.

Upon reaching that point, then I ask on a forum and hope that someone knowledgeable already has the knowledge or can point where to find it (in some form that makes sense).

Been preparing to do a livestream with physics people hired to tutor me through difficult concepts in Q & A style so that people can benefit for free and so that everyone can witness the issue where comprehension plummets with technical content, and hopefully more people with similar issues will step forward.

 

[syfry]

So this thread has nothing to do with the movement of the fixed stars,

Forgot to ask, does this part from Wikipedia mean that the stars do move at a 26,000 year pace, and did ancient astronomers notice?

" ..because the equinoxes moved westward along the ecliptic relative to the fixed stars"

(if you or anyone happen to know)

It's why I asked in the previous comment, but then forgot to include the snippet of text.

 

[Baluncore]

Does that mean they did or didn't notice the stars move?

The "fixed" stars were assumed to be fixed. Early astronomers did not notice any movement.

The farmers and fishermen, who fed the population, used the seasonal calendar. The solstices and equinoxes marked the cardinal days in their year.

Astronomers could also identify the day of the year by observing the position of the Sun against the constellations of the zodiac.

When it was recognised that the two independent calendars were not locked, something had to give. Since the stars appeared to be fixed, it was assumed that the seasons precessed.

Because it takes 72 years for an angular difference of 1 degree to accumulate between the seasonal and astronomical calendars, it took recorded observations over several astronomer lifetimes, before the 26,000-year period of precession could be estimated.