When we moved to the island we currently live on, our address was in a road called 'Solsteinen' (The Sun Stone), but I didn't think anything of it until I realized that the roughly hewn stone serving as the property limit marker was juuu-uuust touched by the sun on Winter Solstice. Aha.

A quick call to the local archaeologist confirmed my suspicion - 'Oh, so you're the new resident there, I'd planned on being in touch - that stone monument has been there for more than 2000 years, is A-listed and please, whatever you do, don't do anything with it. Seriously.'

There's so much old stuff around here that he is basically being called out to perform an assessment every time anyone wishes to build anything.

Where we live now, for instance, there are a handful of burial mounds from God knows when (all plundered long ago), lots of old charcoal pits, a couple of late stone age fish traps in the lake in a corner of our farm.

To exaggerate just a little - where we could build our home was basically dictated by where we could find a spot noone had claimed thousands of years ago...

(Nothing quite like watching an archeologist go 'Oooh, that's interesting!' during a dig to establish whether you can go ahead building on your chosen spot...)

Something like that is happening right now here in Brno:

https://www.novinky.cz/clanek/veda-skoly-po-prioru-zbyla-brn...

A massive construction project & equally massive archaeology operation - mapping the remains of old textile factories, an old channel and rail line, fish storage tanks, a mill, a villa and even a cemetery or two.

The archaeology work is wrapping up in a month or two & then the construction crews will take over the site (they already work in the areas that have been fully searched) to finish the construction project (which includes a 13 meter deep water tight "tub" due to a very shallow water table for the basement levels or 200 meter deep geothermal energy piles, etc.).

Where I live now - same island, but farther from the natural port and, hence, less attractive land in the old days - we still have a few which noone bothered to remove (to till the land underneath or to use the stones for building walls or foundations).

My kids used to love going playing around those mounds, made for excellent inspiration for pretending games, that!

e.g. Work for what is now the Queensferry Crossing bridge uncovered a 10,000 year old home:

https://www.bbc.co.uk/news/uk-scotland-edinburgh-east-fife-2...

They aren't "all over the place" in the US, and I certainly don't have a local archaeologist that I can just call up.

FWIW: The Northeastern US is quite recent with human presence. It wasn't settled until after the last ice age. Pretty much anything old is celebrated because there is so little of anything old.

Fun fact, New England has at least 71 different stonework “prayer sites” that are all astrologically aligned.

Two of the most notable are King Philip’s Cave (Sharon, MA) with a stone aperture through which a "dagger of light" appears specifically during the winter solstice, and Pole Hill (Gloucester, MA) which has fixed boulders that align with the summer solstice sunrise/sunset and the winter solstice sunrise.

Here is a research paper talking about all of them: https://neara.org/pdf/wantofanail.pdf

There are lots of historical preservationists in New England that you can call up. If you want my help finding one let me know where you are located.

So, yeah, there's lots of archaeology in New England, it's just that a lot of it is literally buried or otherwise not called out. (And "in the US, 100 years is a long time; in the UK, 100 miles is a long distance" is also Just How It Is...)

Your "local archeologist" is one of the staff at the state historic preservation society [0], though you'll likely have more luck contacting a local university archeologist if you find anything.

[0] https://www.ohiohistory.org/preserving-ohio/state-historic-p...

Don't take the above as a sign that the natives were uninteresting or stupid. Just that they didn't leave much for us to learn from, both because they couldn't and because what they did was destroyed.

The UK wasn’t permanently settled until the mesolithic either. There are older artifacts like axes, but no monuments.

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

https://daylight.franzai.com/

0. https://drive.google.com/file/d/1FB3Ofl4mUvOO4gGqARro9cO_kjJ...

/edit: Looks like noscript blocks the p5 thing.

You can use an js SVG animation to have it run in real time: https://tomchen.github.io/animated-svg-clock/clock.svg

I have no idea why we stuck with the 12 hour clocks once we stopped using sundials and variable hours: https://en.wikipedia.org/wiki/Unequal_hours

Does the math fail because of not considering (i) equation of time and (ii) oblateness of the Earth ?

fixed it

Thanks for replying.

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

today - 07:18:59 → 16:24:29 = 9:5:30. yesterday - 7:18:23 → 16:23:53 = 9:5:30

I first saw this idea at https://jmw.name/projects/linear-clock/ and then later I wrote a TUI version for myself

I had tickmarks for stuff (when to go to bed to sleep for 7.5h and wake up near sunrise, things like that). I was working on adding a config file format.

Then I lost the project due to a mishap with a pipx flag... https://github.com/pypa/pipx/issues/1324#issuecomment-211885... ;_; o7

One day maybe I'll come back and do it in Rust.

Merry Sun-Fence Day everyone. ;-)

Also fun fact: date of latest sunrise is slightly out of phase with seasons https://xkcd.com/2792/

Edit: Obviously somewhere like here in Scotland observing the sunrise is easier said than done - particularly at this time of year!

Solstice is a small thing they figured long ago, there are things they managed that are much more complex than that. In India there are whole temples dedicated to astronomy and built to align with different celestial geometries.

I started doing astrophotography about three years ago. I'd always been interested in 'space' but never really spent hours upon hours out at night over the course of months actually just studying the night sky. I remember wondering as a kid how people even thought about planets or came up with these wild stories with the constellations...to me it just kind of looked like a bright field of randomly twinkling lights.

Well, when you're out every night from 10pm to 2am looking up, it all just kind of comes alive. You see everything. The motion of the planets, the elliptic upon which they travel, the gradual shift of the entire field as the seasons change, the undulations of the moon and it's varied trajectory across the sky. The shifting of the sun's set and rise and the ebb and flow of day vs night. Everything. Your mind just starts to harmonize with the rhythm of it all. It's pretty wonderful.

The sheer amount of _stuff_ in the sky is mind boggling, the silence is deafening.

That we spend all of human existence until little over a century ago living like that is something I have a hard time wrapping my head around.

However if you live in the open, or have daily access to the open sky, after a while you are bound to notice.

We are so used to having a ceiling above us, so used to constructions blocking our view of the sky that this seems a feat.

I was the same till I got access to the sky. Then ... oh wait ... the sunset is shifting towards those landmarks every day. Oh wait, now its turning around to go the other way.

The total span of movement is so large, that its hard to miss unless you are on a featureless landscape or in the open sea.

I am super impressed by humans noticing and separating the planet's from the stars. Look at those stars they don't twinkle and they move funny. I guess the planets drew attention because of their brightness and by their lack of twinkle.

https://en.wikipedia.org/wiki/Solstice#Solstice_determinatio...

You and I personally may not have kept track, but our local religious leader did, and maybe the even staged a ceremony at the winter solstice to ask the sun to make the days longer.

I find it strange that today knowing much more about sun and moon we don't consider them as gods. Today we know for sure they are the origin of all life on this planet and yet many cultures decided to go for an abstract intangeable entities instead of what is directly in front of us and can't be debated.

After you notice that, if you want more precision, it's the day the Sun rises and sets most on the North/South. It's also the day things cast the largest shadow at noon. You will need some special device to get very precise on the sun raising position (like a pair of stones or something with a hole), and you won't be able to get precision on the shadow thing.

For more modern people, starting about only half a dozen millennia ago, it's the hour the Sun stops moving North/South within the stars and starts moving the other way around. You will need to look at it and take notes many times, and average things out to get any precision. Even more because you can't see the Sun and the stars at the same time, so you have to model them.

They didn't like go out on Dec 21st, and look where the sun was and mark it. They didn't even have calendars like that. They watched the sun every day, and waited until it stopped being lower in the sky at it's highest point in the day (or whatever other sign of the solstice they wanted to use), and marked that angle and built whatever viewport they wanted (a door, tunnel, etc).

Then they could just go wherever they built the thing that pointed at that point in the sky, and go, oh, okay, the solstice is soon, or just happened, or whatever and plan accordingly.

It actually wasn't really accurate to the day, anyway. There are a few days on either side of the solstice where the effect is basically the same for the viewer.

Something to keep in mind is that this isn't only useful for determining the exact date of the winter solstice, which they may not have even cared that much about. You can see roughly where you are in the year on either side of the solstice by looking at how far out of alignment the sun is on a given day. So it could be useful throughout the fall and even well into the winter for gauging the passing of time. People didn't need to plan day by day or even week by week, but they did need to do things in roughly the right part of the year.

People act like this is some unexplainable advanced technology, and anybody can just do this with a stick and some rocks.

December: https://www.timeanddate.com/sun/uk/kirkwall?month=12&year=20...

June: https://www.timeanddate.com/sun/uk/kirkwall?month=6&year=202...

Now if you disclose your local time offset from GMT, say, Palantir can send a drone carrying roses.

Of course this is meant as a joke, but wanted to emphasize how easy it is for location information to leak. And if one really doesn't care about collateral deaths how easy it is to exploit location data.

https://www.etvbharat.com/english/bharat/padmanabha-swamy-te...

Kerala, for the curious, is also the place where the infinite series (and with it arguably calculus) was devised some 200 years before Newton's birth.

Blatant Western-centrism within academia (and the strange, almost primitive-hatred for living ancient-cultures) perhaps hasn't led either to the recognition of "ancient" monuments in India or its scientific/astronomical outputs.

The festival of Sankranti for eg. is so old that due to the Hindu Luni-Solar calendar's usage of the sidereal year, it has drifted off from the winter-solstice by 20 odd days, starting from 150 BC (amusingly as has the Julian calendar, but due to a lack of precision in arithmetic / observational accuracy).

Biased coverage is unfortunately rather widespread in more general media. And rise of nationalisms don't help in the matter. Which is true for western and eastern countries by the way.

Regarding a case of several millennia of prior art, there is Pāṇini, who employed metalanguage long before the idea become of interest in western side.

https://en.wikipedia.org/wiki/P%C4%81%E1%B9%87ini

By the way, Wolfram’s website has an interesting summary of the history of this formula.[0]

[0]: https://mathworld.wolfram.com/QuadraticEquation.html

In India and also in general it's called Sridharacharya formula or method. It's named after the Indian algebraist Sridhar

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

whom Bhaskara quotes extensively.

Enough with this bullshit please? There are genuine reasons why the knowledge of the calculus of ancient Kerala didn't travel outside India during the late middle ages.

It is a fact that Madhava a mathematician and astronomer from the late middle ages, came up with calculus, and established the Nila School of Mathematics in Kerala. For some reason, the book (Yuktibhasa) that discusses this math is written in the local language Malayalam. Most scholars at the time only understood Sanskrit, including later Western scholars who were unable to find good Malayalam book. Because of this, it was difficult to have the works translated, especially since the works describe formal proofs of concepts like series expansion, which was not even known in the Northern India at the time.

Kerala was also under Portuguese rule at the time and was frequently faced with wars, so the school gradually declined and the math culture sort of died out.

The Mathematics of India by P.P. Divakaran discusses these themes.

P.S: Most of what I've said here is taken from this Numberphile video of another mathematician discussing the life and work of P.P. Divakaran (who recently passed away) https://www.youtube.com/watch?v=G23Jx0kPCSI

Newton and Leibnitz get credit because they placed calculus as a general technique that is immensely broadly applicable not just for extrapolating the tangent function or the sin function as a series, but to any function that's smooth in some sense.

They worked out the details that do not depend on the specifics of the function and called them out as rules/results of broad applicability. Especially how to push the differential and integral operations through +,-,×,÷ and function composition sign. It did not matter what the function was as long as it was built up from those operations.

I am familiar with the work of Kerala school and also of Aryabhatta's work on using differential coefficients to extrapolate the sin function (this being much before Kerala school), his work on difference equations.

Rather than getting caught up with us versus them narratives , spend some time learning about the beauty of math and how different cultures have thought about them in such creative ways. Otherwise you risk sounding ignorant and rageful conspiracy monger.

The inaccuracies in the Hindu calendar is and was a lot more than the Julian calendar. The Julian calendar assumed that a year was 365 1/4 the day. This is slightly inaccurate and therefore there was a need to correct for the leap day that's added every 4 years by skipping it every 100 years, adding it back every 400 years. At time of Gregorian correction it was off by 10~11 days because of an error of 10 minutes in their estimate of the length of an year.

Hindu civilization's estimate of the length of an year, although remarkably accurate for its time, was less accurate than the estimate of 365 1/4th. Usually the length of an year has been overestimated, making the Hindu calendar lose accuracy quicker. These errors were order of a day per year versus off by about 10 minutes like the Julian calendar.

This was less of a problem historically because Ujjain observatory would correct the calendar time time using accurate observation of the Equinox. Since the fall of Ujjain observatory the Hindu calendar has been accumulating drift error for centuries.

unless you bump your toe on part of it.

It takes my breath away how consistent the mean length of a day is and how accurately we can measure it. So accurately that if it deviates by mere tens of milliseconds, and it does, we can notice it.

It boggles my mind that a hunk of rock made up of differing densities, with so much of salty water sloshing around, Moon exerting her brakes, bombardments by extraterrestrial matter, Earth still remains so consistent. Of course, this is not surprising if one does the math.

Yes math and physics are different. It's the the fact that math can model the physics so accurately at all that it's breathtaking.

Even without venturing into the realms of Quantam Mechanics, all measurements are, by physical definition, upto the resolution of the measuring instrument. So it always come with inherent +/- error bars. Sometimes these error bars are made explicit, at other times they are elided, often with the assumption that it's obvious.

Models are always simplifications. That is precisely why they are useful. ( A 1:1 scale map is not very useful, especially when we already have one). Models are obtained by ignoring the effect of many known disturbances, but whose effect one deems not to exceed a tolerance bound.

We jump so quickly to religious significance.

In the northern latitudes, doubtful. It would be cool enough year round.

The article talks extensively about how these monuments were used for timekeeping. Marking the seasons allowed people to predict animal migrations and plan agricultural activities.

It seems that you are the one who has forgotten the practical uses of these artifacts.

We bring thermos bottles, some bring kids, pets, and we just stand there in silence watching the sun.

Afaik it's not coordinated, it's just a bunch of people having the same idea every year.

It is built east-west to signify sun’s journey. The temple has a wheel sort of structure which kinda acts as sundial with minute level accuracy.

In India, difference in day time between winter and summer solstices is minimal ( 3.5 hours ), I guess it doesn’t signify anything major close to equator.

[0] - https://www.tribuneindia.com/news/j-k/snow-rain-in-higher-re...

[1] - https://www.tribuneindia.com/news/himachal/snow-likely-on-de...