Part of the long-lost star catalogue of Hipparchus found in medieval parchment | Hacker News Reader

Part of the long-lost star catalogue of Hipparchus found in medieval parchment

nature.com

134 pointsJoeDaDude37 comments

> The phenomenon of precession — in which Earth slowly wobbles on its axis by around one degree every 72 years — means that the position of the fixed stars slowly shifts in the sky. The researchers were able to use this to check when the ancient astronomer must have made his observations, and found that the coordinates fit roughly 129 bc — during the time when Hipparchus was working.

That's amazing, using the discovered results themselves to step backwards and find out when the observations were made.

Back in the 90s, there was a documentary* on the pyramids at Giza that took the wobble into consideration. There are holes that in modern times do not appear to have much significance, but winding the clock back && adjusting for the wobble aligns said holes with significant stars. There's a foggy memory that this theory might have been debunked, but it was the first time I had heard of the wobble being used in such a manner.

*I have no recollection of a title. Just recall watching it on VHS. One of those nights at Blockbuster when all of the "good" movies were unavailable so went to find something else from the middle of the floor

Not the documentary but:

https://en.wikipedia.org/wiki/Star_shaft

Yes, I should have remembered it being Orion. Just seeing your link reminded me how their theory said the pyramids were positioned along the Nile similar to how Orion is positioned to the Milky Way. Now I'm going to read the wiki link to see how my memory holds up.

Edit: yup yup. The wiki link gave the name of the documentary, and of course it's on youtube: https://www.youtube.com/watch?v=cfgRF1e66_8

My history teacher made us watch this in high school when it just came out! She was very into it, at the point where the scholar who works for the Egyptian state starts voicing his criticisms she told us this was the response of a man afraid to loose his power :)

Yeah, all of the naysayers were a bit off putting in a weird way to me about this. I understand it's a "new" idea (at the time), but it just seemed so dismissive. It's very compelling information, and a very interesting idea. The arguments against were not nearly as compelling to me.

It’s a slightly different take on it but there’s a popular TikTok account (and I assume a related community) where people find old globes and then try to pinpoint when they were printed based on the labeling of disputed territories, renamed countries, redrawn lines etc. Its fascinating how specific they can get.

https://www.tiktok.com/@jakie62/video/7140007175476235562

https://xkcd.com/1688/

Of course there's an XKCD for that. Amazing, thanks for sharing.

This sounds like a kind of historical GeoGuessr.

I remember back in the early 90's seeing for the first time a post-WW2 map that just said "Germany." Not East Germany and West Germany, but just Germany. Stood and stared at it for while with a weird mix of emotions.

Somewhat related, but the Earth's rate of rotation changes somewhat randomly over the centuries due to tidal friction, tectonic motion, and climate change. These random perturbations add up, so over the course of a few thousand years, the rotation angle of the Earth can be uncertain by up to 70 degrees or so.

But because total solar eclipses occur at times that we can calculate and are only visible from specific locations on the Earth, geologists have been able to use ancient accounts of solar eclipses to constrain the long-term change in the Earth's rotation rate.

Just a question: 70 degrees in just several thousand years? Is that a mistake?

Those were the numbers I saw when I was looking into this a few weeks back.

If you think about it, a few millennia corresponds to ~1,000,000 days. So to know the rotation angle to within 10 30 degrees or so, you need to know the length of the day to better than one part in 10^7. But each year the length of the day changes by a few tenths of a millisecond, which is about 3 x 10^-8 of the length of a day. So you have to know the change in the length of the day reasonably well not only today, but at all times going back 2000 years.

Those few tenths of a millisecond add up over thousands of years!

Ah, I see where your number comes from. However, those deviations should happen in both senses (adding and subtracting)? But thanks for the computations!

They do but in the long run because of the tidal forces of the moon days become inexorably longer.

Wow, thanks for the details!

He means 70 degrees of rotation within the daily cycle, so roughly 5 hours of rotation. (He's not talking about the rotational axis orientation being off by 70 degrees.)

5 hours over thousands of years is known to be within the margin of unpredictable irregularities. Nowadays we compensate for these irregularities by altering our timekeeping by way of leap seconds.

I got this idea late, thanks. My mistake. That makes sense.

The precession of the earths axis is around 26,000 years for 1 cycle. What's incredible is that the ancient babylonians were able to detect and measure this at the time.

Paper: https://journals.sagepub.com/doi/10.1177/00218286221128289

Thanks! I still haven't found a photo of what I expected would look something like a star map with dots. Is the hidden text basically a list of coordinates and descriptions?

Yeah I think "catalogue" is a better word and that's why the paper uses it, I don't think there is a visual "map".

I'm slightly annoyed by the description "first known map of night sky" because medieval is late, and there must be some cave paintings or carved stones with the sun and the moon at least. And "first known" must mean "earliest surviving", because wouldn't there have been a few maps in the Library at Alexandria? What about China?

It's Hipparchus which dates the original, and doesn't make what it is less cool, but my brain thirsts for a little more clarity/context in the headline.

Ok, we've put Hipparchus up there.

It's surprising that no one has applied ML techniques to historical documents like these. Scanning the documents to uncover some text that was overwritten would be a very useful technique for historical research. Written documents have very distinct statistical properties and if there is a big enough corpus of text then it would be easy to train a classifier to uncover the statistical properties that are not clearly visible but still have the distinct statistical signature of written text.

Presumably we are on the verge of AGI so this seems like a very easy application.

What makes you think no one is?

https://en.wikipedia.org/wiki/In_Codice_Ratio

Mostly because it is an academic exercise and lacks obvious incentives for profit but it's good to know there is such a project. Seems like my idea was right on the mark.

Thanks for the reference. It says that the project was started in 2017, have there been any interesting discoveries since then?

There are tons of teams working on historical document analysis, just look at e.g. ICDAR.

Working with historical documents is just very hard do to poor data quality and availability.

One day, the Vatican vaults will be cracked open, and the amount of history we'll be able to piece together that we've been denied for centuries will make people shake their heads in disbelief.

The Vatican archives are mostly open to researchers already.

Right: if they already know what they're looking for, because if they don't their application's just getting denied. No free roaming the archives. So that's a radically different situation compared to "here's what we have, everyone can access it."

No making a copy of it and putting it up for free on wikipedia, eh?

I don’t think wikipedia would want to be a primary host. Maybe internet archive.

It's not a map but a catalogue with coordinates.

Look for Connections by James Burke. Try YouTube.

Every computer engineer, computer scientist and software developer should learn about the Jacquard loom and its predecessors and its significance as elegantly described by James Burke.[1]

[1] https://www.youtube.com/watch?v=z6yL0_sDnX0&t=35m50s

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