[Closed] Number of days in a year question

solstice to solstice ?

and some kind of solstice detector

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"Solstice Detector"

🙂

[url=Calendar]Calenders. [/url]

Wiki FTW.

I can't thnk of stonehenge without this sprining to mind:

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As above, on earth: longest day(light) to longest day(light) is roughly a year.

Don't know how you could work it out on a planet with a 'vertical' axis though?

Welcome to my world! 😀

Determining the precise hour value of a year was one of the primary sciences for scholars (monks/theologians) in late antiquity through the middle ages, and was one of the main disciplines of the great academies of the period.

Tides, moon phases, and shadows were observed and the data collated with a view to working out the difference between solar movements and the lunar year, and establishing an exact value for the solar year.

Ultimately, the whole enterprise allowed the Church to establish with precision the exact date of Easter, and gave the world the most accurate astronomical system and, in the end, an accurate calendar.

Many thanks - SaxonRider, if I was on another world would this be the best way to calculate a year?

Well, of course the year would be of a totally different value on another planet, so while the techniques would be the same, the results would be different.

Unless of course, there was another planet exactly like Earth. Which, I suppose, there could be...

If you landed on a planet such as Venus where the day is longer than the year that will really screw with any logic we have regarding calculating days.

If you landed on a planet such as Venus where the day is longer than the year that will really screw with any logic we have regarding calculating days.

Not really - a year is how long it takes for the planet to orbit the sun, a day is the time between two successive noons. They're independent numbers.

Don't know how you could work it out on a planet with a 'vertical' axis though?

If you know noon, you can work out midnight. Look up and see what star is directly overhead at midnignt, wait until you see the same again, that's a year.

Wisdom of the Ancients, my arse - it's amazing it took them so long 😉

If the planet has a tilted axis like earth, all you need is a stick, pen and paper, and good weather. And a timepiece of some kind of course if you want to express it in terms of earth time.

Each day the end of the stick's shadow describes a parabola across the dirt. The point where the parabola is closest to the stick is noon. If your planet has a tilted axis then it has seasons, and from day to day the closest point to the stick will be vary. The closest it ever gets will be noon on the summer solstice. You just need to record this and measure how long it takes to come round to that point again.

Of course if you are a mathematician or you have excel, you would only need yo take a couple of weeks' readings then you could fit a sinusoidal curve to that data to predict it. Means you would not have to wait a whole year.

Molgrips just a question as this stuff fascinates me, hence why a day being longer than a year screws my head up even though I understand the rationale, but would it be sinusoidal or would it be parabolic the formula you used?

molgrips, if you are up for a beer, I wouldn't mind having a conversation about that.

I would enjoy that conversation but I fear most of it would be over my head!

would it be sinusoidal or would it be parabolic the formula you used?

It'll never be sinusoidal - depending on the time of year, it'll be parabolic or hyperbolic, or (if you're above the arctic circle in summer for example) an ellipse.

It did take a while to get the length of the year 'exactly' right. When the Julian Calendar was switched to the Gregorian in 1582 the correction applied to compensate for the error from having a leap year [i]every[/i] 4th year with no exceptions was 10 days.

http://www.hermetic.ch/cal_stud/cal_art.html

You'd just wait for father christmas to come and then count till you saw him again.

righto,what about days in a month?
why does february get short changed and poxy march has 31 days?
why not spread the love? more equally speaking

pleaderwilliams - Member

As above, on earth: longest day(light) to longest day(light) is roughly a year.

Don't know how you could work it out on a planet with a 'vertical' axis though?

Am I right in thinking that the tilted axis on our planet is one of many features (as compared to other planets size, distance from their suns, number/size/distance of moons etc etc) that made ours capable of evolving so many and such diverse and complex "carbon-based lifeforms"? ..that is to say that if you lived on a planet with a vertical axis then would there be anything evolved on it clever enough to wonder how many days there were in a year?

PS I still like the Revolutionary calendar with its fancy month names. Germinale, anyone? 😀

sausagefingers - Member

righto,what about days in a month?
why does february get short changed and poxy march has 31 days?
why not spread the love? more equally speaking

Simply put, the month is determined by the lunar cycle, which makes for a 28-day period. But 12 of these periods do not make for a full year (it takes 12.37). As a result, both intercalcated days and months were deployed in different calendars to make up the difference. We still do this ourselves with the additional day in February every four years. But the history of that whole month was always shakey, as it was seen as a tack-on at the end of the year, and the number of days it had could vary.

This was the case until Julius Caesar.

molgrips, if you are up for a beer, I wouldn't mind having a conversation about that.

Aren't you in Cardiff? I'm wfh until the New Year now, a bike ride might be on the cards 🙂

It'll never be sinusoidal - depending on the time of year, it'll be parabolic or hyperbolic, or (if you're above the arctic circle in summer for example) an ellipse

Thanks ben - I said parabola, but it was just a guess - your answer is much better 🙂

Doesn't matter which though, the formula still works.. but only really when the day is much shorter than the year. Not sure what to do if it's not.

On the subject of days in months - the Romans originally wanted there to be ten lunar months, which is why from September onwards their names contain the numbers 7, 8, 9 and 10. However that only adds up to 304 days so according to wiki the remaining days just didn't have any date.