# How did the ancients people track time accurately to know the solstice ?

I see on the newscast the last couple nights that yesterday was 1 minute more daylight than the day before, and today 1 minute and some seconds more.

I know that the Winter solstice has been celebrated for thousands of years. However how did the ancients know this? What manner of keeping time were they using to determine one day of the year was the shortest day for daylight, and the next day was a longer period of daylight by 1 minute?

They did it by observing where the sun rose and set each day, a la Stonehenge.

You don’t use a clock. You use the position of the sun at sunrise and sunset. Stand in one spot every day at sunrise and sunset and mark the position of the sun on horizon. As the solstice approaches you’ll see the sun rise farther and farther south, and set farther and farther south. The day after the solstice the sun rises farther north instead.

The equinoxes are when the sun rises due east and sets due west.

Note that, in the few days in the vicinity of the solstice, the sunset (or sunrise) position changes only very slowly (hence the name: “solstice” = “sun stationary”). But you can use some landmark to mark a more significant change, and then split the difference from there. Like, for instance, suppose that the December sun spends a few days just south of that tree over there, as viewed from this rock: You then note the days when it’s exactly at that tree. And if you notice that those two days are six days apart, then three days after it first reaches the tree, there’s your solstice.

Sir Fred Hoyle pointed out that certain sight lines at Stonehenge (not involving the massive central stones that were later additions) were set out not exactly to observe the solstice but to where the sun rose five days before and five days after the solstice and this was true both winter and summer. These would not work that way today on account of the precession of the equinoxes (QG).

The unstated part of the equation is that you’re already a decent astronomer before you’re ready to predict when the solstice will occur.

You already know how the path of the sun in the sky is changes from day to day and you understand that it relates to the days getting longer and shorter. Once you go through the cycle a few times, it’s not too hard to say that once the sun rises in a certain location, that’s as far as it’s going to go and the next day starts it back the other direction.

And who was going to argue anyway?

On the radio on Monday afternoon, a presenter was talking to a listener who was in a car. The listener said that he and his mates had been to Stonehenge for the solstice. The presenter said, “But it’s not 'till tonight.” The listener was adamant that it was on Sunday 20th.

He must have felt pretty silly when he read in today’s paper about the big crowd that was there yesterday.

And you don’t need a Stonehenge like structure to do it. My living room window looks East out into a courtyard with walls facing exactly North, South, and West. While I have never tried to map the path of the sun, it would be simple to track any celestial objects as they rose above the opposite wall, and the shadow length would help track the angle of the sun.

I can’t believe you guys are not mentioning the secret knowledge imparted to our ancestors by Ancient Aliens. I saw it on TV just the other night!!

On or about the solstice, there is one particular street on my morning commute where the sun lines up perfectly with the left turn signal when I’m sitting in the left turn lane. Damn annoying.

Better yet, Manhattan Henge.

Manhattanhenge

The road my house is on runs exactly east-west with lots of tall trees on either side. When I come home in the evenings on the equinox the sun sets neatly down the line of trees. Cool effect.

Precession shouldn’t present any problems for Stonehenge-style observations. The equinoxes and solstices are defined in terms of the movements of the Sun, and that’s what Stonehenge is used to observe. Precession only becomes an issue when you’re tracking the seasons by means of the nighttime stars, such as the ancient Egyptian use of the heliacal rising of Sirius.

There are usually traffic slowdowns on busy east-west streets at the equinoxes.

I stand corrected. What Hoyle actually said was that Stonehenge would cease to be an accurate eclipse predictor on account of the precession. Since hardly anyone credits his theory that Stonehenge was an eclipse predictor since hardly anyone believes that the ancients could have understood astronomy that well, his theory has not caught on. He actually went on to speculate that after the eclipse predictions started drifting, they had lost the theory and then brought the massive central stones there in an attempt to propitiate the gods.

One claim he made is clearly correct: he could have used Stonehenge as an eclipse predictor.

Just from observing shadows cast by tall objects (like a tree or a flagpole) you can see that shadows get longer and shorter throughout the year. The day with the longest shadows is the winter solstice. The day with the shortest shadows is the summer solstice.

If you had some patience and persistence, it wouldn’t take much knowledge to make a line of rocks, where each rock shows the point on the ground where the tip of the shadow touches at the time when the sun is highest in the sky that day. You’d discover that these 365 rocks would form a tall skinny figure 8. After you have this set up, you don’t really need to count the number of days, just go outside and look at your sundial and see when the longest shadow reaches the farthest rock.

Remember, in the Good Old Days there was not much else to keep people amused; plus, in these days of books, calendars, and smart phone reminders, we forget how much work and detail people could track in their heads. By the time people were settled in cities, they had figured out calendars and how many days per year. (Presumably they had noticed the need for leap year adjustments, too)

As others point out, the behavior of the sun and stars can be easy to track, too, by lining things up and measuring shadows or line-of-sight. I assume the local shaman or priest knew - “the sun rises this far south but no further” since tracking seasons was important to any agricultural society. Once you know northern-most and southern-most travel of the sun, it’s pretty easy to find the middle point. Since the sun’s position is changing pretty quickly then, that’s even easier to pinpoint to the exact day.

So I guess the short answer is - they figured it out.

I guess before the Internet and TV there was precious little else to do

I’ve been inside Maes Howe - a chambered cairn in Orkney, where the setting sun on the winter solstice shines down the passageway and onto the back wall. They knew when and where this was going to happen well enough to build this remarkable structure.