A brief History of the Calendar and Time Keeping

thank you very much for the introduction so thank you very much everybody for coming tonight as yapper introduced I'm Donna Carroll and I teach physics here at the University of Maastricht tonight I want to talk to you as you can tell from the title I want to talk to you about time and time is a huge topic so there are so many things that one could discuss about time it's possible to look at time from psychological perspective so if you're having a really boring day time could go very slowly and hopefully that won't happen this evening I'm a physicist so you might also think that I'll be talking about relativity theory and time dilation but actually what I want to do is go back to the real basics what is time how do we measure time how and who has decided how to divide time up into the divisions of time that we use on a daily basis so those are the things that I want to discuss tonight I'm going to start by by taking you back to the time of ancient man if we want to discuss what we mean about time we need to think about how we perceive things changing around us so if every day nothing changed then time for us would perhaps feel unlimited some some of my students there in the back there they might think that some of my lectures feel like that but fortunately for us we see things changing in nature and because we can look at the natural rhythms and repetitions around us we can use these as a sort of benchmark for using a measurement of time so if your ancient man can I just check is the volume too loud on this no okay sounds very loud down listen okay so if your ancient man and you're sitting in a field then the first repetitious cycle that you notice in nature is of course the day and the night cycle so it's very easy to see where our divisions of day and night light and dark come from so that's very obvious cycle to start with so I'm not going to explain days any further than that the next most obvious cycle that we have a perception of the passage of time is the waxing and the waning of the moon and the the word moon giving us the word month so we can see that this cycle changes every 29 days to every 30 days you get this waxing and waning pattern and of course for ancient man if you turn off all your street lights and you didn't have the big cities around then of course this is something that's very easy to spot and it has a big impact on your life so the first calendars and the first time measurements that you see appearing are Luna based calendars so there are many different examples of these that have been found things like notches on Nawal bones you also see examples of where ancient man have dug pits so little circles in fields and they're drawing out a sort of very very basic lunar calendar so that's one of the first calendar based systems that you see coming into existence of course we've talked about days and months the the next cycle that is obvious to see and maybe it depends on on which part of the the world you're living in but for us living in this part of the world is very obvious to see that you have the passage of seasons so at the moment it's cold weather and we it's very obvious to see that you go through the four seasons and that gives you an idea that something is changing and that gives you an idea of what's going on with what we call the tropical year of course getting a measurement of the year is very difficult right because I can't use temperature to give me an indication of exactly has a year passed if it's now eight degrees again so this is where certain civilizations had a better idea of the length of a tropical year than other civilizations so for example if you look at what happens the the Nile every summer it floods its banks so the Egyptians had a huge advantage over other places in the world with being able to accurately measure the length of a year because they built these things these structures called Nile emitters which I think is a great name so these Nile orbiters as a sort of pit or a well in the ground with stairs coming up and every year these would flood and they could measure the the height of the flood and that gave them a really good indication of the length of a year the other things that you can do to measure the length of a year you can look at the position of the Sun as it moves across the sky so anyone who's who spends a lot of time outdoors you will notice that the position that the Sun is rising on the horizon and setting in the horizon changes as you go across your year and the position of the noon or the midday Sun is also changing across a year so that's why you see structures like this like in Stonehenge which is very famous but there are many other examples of this which were designed to measure the length of a year a solar year depending on the position of the Sun so you would wait until the Sun returns to that same position and that gives you an excellent indication of your length of solar year if you look at the the position of the Sun at midday precisely noon every day of the year you will also see that the Sun draws out this beautiful shape across the sky and you see photographers doing this with very fancy sun filters and this shape is known as an analemma and actually if anyone's got kids at home this really nice experiment that you can do you don't have to do this with fancy fancy cameras and fancy equipment you can actually do this looking at shadows so if you stand in the same position in your garden or if you use a little nomen a little stick in your garden and you measure the tip of the shadow where it falls at noon every day or perhaps weekly or two twice sorry once every two weeks across a year you will also see this beautiful and a lemon shape being drawn out so these are all different ways of measuring the length of a year so firstly the tropical year this is now the solar year finally the the other method that can be used to measure the length of a year is looking at the positions of the the stars in the sky you will see that from our perspective on earth they also appear to be moving around us of course we know now that the that we are moving around the Sun and the background of the stars is actually stationary but it appears from our perspective on earth that the stars are moving around us and the best way of viewing this is seeing which stars come up on the horizon at a certain time normally people use sunset or sunrise so that they have a position to compare against so this gives you an idea of the length of a side aerial year coming from the word star so this is a sidereal year so you can see that I've already mentioned we've talked about days months and now three different types of years that it's possible to measure now this is it becomes a very complicated system because the number of months don't doesn't equally go into the length of a year so this creates really a lot of complications and the wave in which you decide to measure your year and the type of year you're choosing to measure also has an impact on the kind of calendar system that you can develop but it's possible to see that from a very early stage these repeating cycles in time these indications of a passage of time were very influential for civilizations so you can see way back to the ancient Greeks if you look it's approximately eighth century BC you can see in the works of Homer people are already using the position of stars and the position of the Sun to be able to navigate people are already using this kind of information to decide to make agricultural decisions when should we sow our seed when should we harvest so calendars in some form are already very important to these ancient civilizations these days we have calendars that have developed from all of these different meta measurements so you have Luna based calendars such as the Jewish calendar you and then you have calendars that are based on the solar year and also this idea year there are I think more than 40 calendars still in existence today and I'm only here for an hour so I only have time to talk about our calendar so that's what I'm going to stick to as a topic today so our calendar is a Roman calendar the Romans were heavily influenced by the Sumerians and the Babylonians before them so some of the ideas that they they were influenced by come from all the civilizations however our calendar is a Roman calendar and it originated from Romulus who was the first king of Rome he decided to try and sort of make a mismatch of two different type of two different types of candidates we've already looked at the lunar system and we've looked at the solar system and he was trying to sort of force these into one type of calendar and these types of calendars are known as lunisolar calendars now back then the Romans had a reverence for the number-10 most probably because they used the ten digits to count with so it was a very convenient number to use and you can see back in history that Romulus actually he liked the number 10 so much he divided his Senate into tens he designed he divided his military into tens so what he decided to do was hey we're going to have ten months in a year and this is how our calendar started which is kind of complicated thing to do so here it is ten month calendar and then he had these sort of extra days that he didn't know what to do with so his calendar looked like this it began in March because the year begins in March it's when spring begins it's when things get born you know seems like a good time to start a calendar so March and you see here the lengths he he gave these months and also weather names originated from so the first few months were named after Roman gods and then he kind of ran out of God names so the next few months would literally just named after the number of the month so you can see quintilius Quint is the the Latin for five we get sexed we get September October November and December which are quite familiar to us and this is the reason why Sept is comes from the Latin word for seven and it was originally the seventh month so if any of you have looked at your calendars before and you've thought well I know acht means eight why is it the tenth month in the calendar that's because January and February didn't exist in this time so this these were the first original ten months now if you add up all of these days you get these 61 sort of leftover days these were unlucky days and or thought of as unlucky days and they were so unlucky that they didn't want to give them a name so they were just sort of hanging on there in the winter after December and they sort of known as into kaleri days days that belong to a month with no name and they're there to pack out the calendar because what you want is to have months that are related to the lunar cycle but the year is related to the solar cycle so in some way you have to get them to match up even though in reality they don't match up properly okay so that's what his original calendar look like now the second king of Rome was Numa and this was only about 40 years later and he went well you know odd numbers are lucky so let's change the months around and get rid of these 30-day months and turn them into 29-day months and then we're still left with the 31-day months and it was his idea to create two new months so this is where our January and February came from you still had the problem that there were these like a few into calorie days that were left over so instead of what we have now which is this leak a system where we have a leaper day so we've got a leap day this month in fact they had a few they had a few days that they would package up into like a leap month that they would have every few years to keep the lunar cycle and the moon in sync with what was going on in the solar calendar so that's what they decided to do so his calendar now started with January February and then there was this third month called Merced dounia's and that was the inter calorie month so it wasn't every year it was just every time they decided things were slipping out of alignment so they had to stick that month in there and he changed all of the the 30 day months into 29 day months because of this fascination for odd numbers okay so let's talk about Macedonia sand the reason why we don't have that anymore the word merced Onias comes from the word mercies which means wages right so in this month was actually the month when people got paid soldiers got pay dearly for instance and at this point in time calendars weren't public so people didn't know what the date was the the high priests were in charge of keeping the calendar and they would announce important days to the public so that's the only way that you knew what date it was if an announcement was made so it was up to the high priest to decide when merced o Gnaeus was going to be introduced as an inter calorie month well sometimes the high priest decided to use this to their advantage if they like the politician in office and they wanted them to have extra time in office before the next elections then they go ah let's let's add in another month there if they wanted to charge people more interest for instance or they wanted to skip out on paying people Oh we'll just skip the payment month this year so there was a lot of random introduction and disuse of this month and what this meant was that everything kind became very chaotic and slipped out of alignment and that's something that I'm going to go on to talk about but first I want to talk about the other big change that new mermaid he decided to fix how the the days of the month were named if you if you look up a Roman calendar on Google you see this kind of thing and you might wonder what what did it what how do you read this thing what did a Roman calendar look like so I thought it would be fun to do because I'm a physicist and I think this kind of thing is fun I decided to take our calendar and superimpose a Roman calendar on the top of it to see what it would look like right so this is February of this year the first thing I got to say is that Romans didn't have a seven-day week I'm going to come two weeks later and so it would have looked slightly different so they had they had their them their monks in lists right rather than in this but so that we understand what's going on I've drawn it out exactly as our calendar looks this month so the first thing to label is the Kalin's the Kalin's is the first day of the month and when people like the Babylonians used purely lunar calendars the Kalin's was always the day of the new moon and this is where the word calendar comes from from the word Kalin's so the first of the month they wouldn't have had numbers the first of the month would have been the Kalin's of February the next day that was named was the eyes and perhaps some of you have heard of the Ides of March the word Ides means to divide so we would literally be dividing your month in half so for short months that were 29 days then the the Ides would fit a fall on the 13th for longer months it would fall on the 15th the nones nones like the word novum in November means 9 so 9 meant Romans do this thing they count backwards and they count inclusive so think like a Roman and you go from the Ides and you count back by 9 inclusive of the Ides so this gives you 1 2 3 4 5 6 eight nine and the ninth day before the Ides inclusive of the Ides is then the nomes everyone with me so far good right they do this thing where they count backwards and the for the first day that is behind something one of these days is known as a pre dear this apparently somebody who speaks Latin has told me that this is pronounces preview so the pre genomes of February would be the day before the nones of February hence the pre Dia Ides of February the day before the Ides and this would be the pre G of the Kalin's of March because obviously the next day would have been the Kalin's of March so that gives you that date and then all of the rest are just given a number that counts back from either the Kalin's or the nones or the Ides so this and don't forget they count inclusively right so I'm getting lost myself so this is the day before the Kalends of March but this is the third day before the Kalin's are March because you count from this one so you include the one that you can take from so one two three and then this would be the third I'd this would be fourth eyes I can fill this whole thing in today is the 13th kaylynn sorry the eighth calendar of March because we're counting back from the kale end of March so that's what day we're on today and I can fill these things in take away the numbers and that's pretty much what a Roman calendar look like and the other thing that they did is if there was a feast day or a bank holiday so we had carnival here in Maastricht a week or so ago then they would be highlighted in red on the on their calendars on their written calendars and that's where the term a red-letter day comes from so they're their calendars would look like this so these are each of the months so this is January February so basically they listed everything and as I say they didn't have the seven-day week actually what they did was they labeled all of their days a through to hate and then a through to hate a through to hate and what they had was a sort of eight-day market week so in your area your market day might have been on the letter B so the next time the becomes R and that is your market day so that's how this worked one disadvantage of having a calendar like this is I've already talked about a calendar reform I talked about how numa change the amount of days that they were in the calendar well if you do this and you count like a roman this makes things horribly complicated right so anybody got a birthday in February when's your birthday 2nd of February okay so let's pick somebody else okay no so the problem is because they can't count backwards say if your birthday was that they're the for example this week right so where are we at the moment we're on the 8th Kalin's of March today if I decide I'm the next Roman heir King and I decide to take away two of the days then when should I celebrate my birthday because all of these numbers then shift so would I celebrate my birthday today as it is or would if I took these two days out of February would I then have to celebrate two days earlier so when they made these reforms people didn't know when they should celebrate and actually some people ended up just celebrating twice so things got really messy with with the Saints days and and feast days and things like that so it's a horribly complicated system so I said when I talked about Numa he decided how we were going to call all of the days in the calendar but he also introduced this merced o Gnaeus this into calorie month but people just decided to add it and with tracked it whenever they wanted and what this meant was the entire year had kind of moved out of alignment so don't forget in March was supposed to be aligned with spring well by the time we get to 46 45 BC the the year had gone so far out of alignment due to this into calorie year that actually the springtime was happening in the middle of winter or march was happening in the middle of winter or winter was happening in March you know what I mean that's what I'm trying to say is it was cold right so they knew something was wrong and Julius Caesar them made the next reform and what he did was he decided to get everything back in line by introducing all of the days that had shifted out of alignment into one year so in the year 46 BC he decided to add all of these extra days so that the year was actually 445 days long in total and that brought everything back into alignment it shifted March back into the spring time where it was intended to be after that he also introduced a leap year system which is very similar to the leap year system that we have now so he decided that there should be a leap year he'll get rid of the inter calorie month and we'll have a leap year system and a leap year once every four years so January and February were still there Merced onus was abolished he changed some of the year here we go again he changed some of the the numbers of days in the in the months to get things close to alignment and then we had a leap year and the Senate was so happy that they decided to rename quintilius to julius which is where we get July from I have a thing about why do we need into calorie days but I've already mentioned that things just don't line up we want there to be order and we're trying to measure order but actually the the rotation of the earth on its axis and its orbit around the Sun don't match up exactly so that's why you need these into calorie days months or leap years as we have now two years after he reformed the calendar Julius Caesar was killed people thought that's because he messed with the calendar because they thought well the calendar is god-given right decided by the Sun the Sun comes from God so this is the reason why he's been murdered but what happened then after he tidied up the calendar and he'd introduced the leap years well after he died all of the high priests kind of went what was the rule yo a leap here every three years was it and they literally put a leap year every three years and everything just went hot like completely out of alignment all over again so about 40 years later or Gustus had to come and fix everything again so you get another reform taking place so Augustus decided to correct all the mistakes that have been made he did this slowly over a 16 year period so instead of putting loads of days in to put things into alignment within one year he did this slowly over 16 years adjusting the days here or there so eventually it came back into alignment however the leap year system with having a leap day like every four years is actually too long by 11 minutes now 11 minutes a year doesn't sound like a lot but if you think this was in 8 BC right so 11 minutes a year over thousands of years mater makes a huge difference over hundreds of years so this is a point that we're going to come back to a little bit later anyway again the Senate was so happy that they decided to name the month of six delious after August us and that's where we get the month of August from also because July that was named after Julius Caesar had 31 days there was no way that the month of August us was going to have 30 days so he had to get one more day in his month as well so things kind of got moved about a little bit more so this is how things stayed for a little while I'm going to jump to Constantine who is the first Christian Emperor he introduced the seven-day workweek so this is the week that we have today and he also introduced Sunday as a holy day so where did the days of the week come from that's the next thing on the schedule so this comes back to a Babylonian system if you look at the guy you see the stars they are all generally moving together across the sky at the night overnight and within a year everything comes back into alignment but you'll notice that there are certain celestial objects that don't follow the same pattern as the rest of the stars and in Greeks they were known as The Wanderers and the word Wanderers in Greek is planets so they knew that there were seven what they refer to as planets but they also included the moon and the Sun in this case these were the seven Wanderers and these were special because they didn't stick to the same rules as everything else they could observe so what they did is that they put these seven planets into a hierarchy depending on the period of orbit around the Sun so they had this list and you might think okay we've got seven planets that's where we get our seven days from but the Babylonians didn't make life as easy as out so what they actually did was they took the 24 hours in a day and they named the hours in the day after the planets okay so if I label all of my hours with all of the planet names in hierarchy order obviously I run out after seven so I keep doing that and I keep doing that and seven doesn't go into 24 nicely so what you have is in the next day is you have a different planet at the start of the next day and if I go across it takes exactly seven days for this pattern to repeat and it was the first planet of the day which was known as the dominant planet and it is these days that give our week our is these planets that give our days of the week their names and this is really obvious to see with some of the planets so Saturn and Saturday Sun and Sunday moving and Monday the others are easy to see in certain languages so I've picked French here and that's very obvious that you get Mars day and Mercury Day what happened was that when when the Romans invaded places like Britain and Germany the British decided that they wanted to take on some parts of Roman culture but they didn't want to take on everything so what they did is they change some of the day names to be the same as anglo-saxon gods instead and you see equivalences of these four German gods as well giving you the day names in Dutch in case people were wondering when Christianity took hold in Rome then also Sunday was often changed the day of the Lord which is why you see a different name for Sunday in some languages the the other thing that he did was he convened the Council of Nicaea this was a big Christian council of about 300 bishops they had to decide on some theological disputes that people weren't had there was no consensus on a few things during this period but one of the other things that took place during this council is that they wanted to come up with a formula for the date that Easter was celebrated before this date Easter was it was known that Christ was resurrected during the Passover the Jewish feast of Passover so they'd always followed the Jewish calendar but at this point they wanted Christianity to move away from its dependency on the Jewish religion it's a completely separate religion we shouldn't be relying on their calendar was there thought at the time so they had this meeting to decide what the what the formula for Easter would be and they decided that Easter was going to be on the first Sunday after the first full moon after or on the spring equinox so that's the rules for Easter and when it's celebrated however you need quite good astronomy to be able to work out exactly when the spring at spring equinoxes and also the spring equinox can happen at different times on different parts of the earth so there's some disagreement or they could be disagreement about the exact date so instead of using astronomy to work out when their equinox was they just set the Cranach says the 21st of March so that's how Easter was left and this is going to come back to us in a little while not so long after this council was the fall of Rome and you enter into the Dark Ages during this time a lot of information was lost but this is one area of history that I find very interesting normally people think perhaps religion and especially Christianity and the development of science are very much divergent things they contradict each other but actually this is a period in time where if it wasn't for the fact that the Catholic religion at the time wanted to know the exact date for Easter that's why science was promoted during this period astronomers were very important mathematicians were very important because people needed to be able to make these calculations so one thing was promoting the other so during this time in the Dark Ages monks were very busy also thinking about time they needed to know what time to pray they were also Dennis the smaller yeah I can remember his name in Latin it now Dennis yeah Dennis the small deciduous exiguous or something like that anyway he did a lot of work on looking he developed the ad and BC system that we use today and it's worth historians noting that before that was implemented actually years were just discussed on who's who was raining at the time so you didn't have 800 BC and 59 BC you didn't have that kind of clarity you would say oh that was the second year in the reign of and you're specifically talking about an emperor king who's raining at the time that's really confusing because then you have to have historical context about what was the order that people were reigning in otherwise you don't know and what happens if somebody comes into power halfway through the year is that their first year or is the next year their first year so this means that there's a lot of doubt if you look back in history recall text over exact dates during this period now if we move a little further forward you see certain developments so things like the printing press and trade and communications were travel was improving during these periods so actually the calendar was made more public because of having printing presses and that meant that people were aware that actually I said that the Julius Julius Caesar's system of having a leap year every four years was slightly flawed is 11 minutes too long now this was hundreds of years later and people are starting to notice actually people are celebrating Easter at the wrong time because it was possible to see with astronomical observations that your 21st of March which was set as the date of the spring equinox was drifting away from the spring equinox the spring equinoxes when your days in your nights are of equal length because there you have no tilt towards or away from the Sun at that point so this was easily spot able so the problem is is that the Christian religion at this point was being mocked by other religions people are saying well if you're celebrating Easter on the wrong date well then you're stuffing your faces when you should be fasting right so you're making a mockery of your own religion and this is something that really had to be fixed but mathematics wasn't good enough at the time so nobody really knew how to deal with this and nobody really had the power to deal with it although there were a lot of attempts it wasn't until the 1500s when Gregory the 13th had had enough backing to be able to implement a further reform and it's actually the Gregorian calendar that we use today so he decided which year to use and I was talking about tropical years so the years and things like that and he decided on a new leap year system this if you see the the years that this was implemented it was implemented in 1580 - this is an interesting period because the church was trying to at this point stamp down its Authority a little bit more clearly straight after the Reformation so this was in some countries this river this reform of the calendar were seen as a papist plot so he decided to fix the calendar and move everything back into alignment by removing ten days because the calendar we'd been adding eleven minutes to the calendar for hundreds of years so it was now ten days out of sync catholic countries tended to take on this reform quicker than others Protestant countries took it on late it was chaos because in this country for instance the the Catholic areas in the south took on this new reform whereas in the north they didn't so in one country you had places being ten days out of each other so the calendars were really confusing at this period there's also people saying that there were riots in the street because people were like I've lost ten days of my life and people were saying well I'm not going to pay I'm not going to pay my rent for this month because it's ten days shorter I should have a 10-day discount there are all these sorts of arguments against it for instance the the Orthodox Church didn't take this on until the 1920s and even now they still calculate each suitor to the old date so they've taken on in some parts and not other parts the UK for example took this on nearly 200 years later 1750 - and they took it on so long after that they had to take off another day because it was already 11 days out of sync so this would this was a huge mess it didn't really bother people very much at the time because there were no newspapers and there was not as much travel and people saw it as just just checking in your your date when you travel like in the same way that we check in our money if we want to travel abroad and change it's something else so it affected people personally in some ways but it didn't affect countries like you might think it would today so his new leap year rule was that you skip you have a leap year every four years apart from all the centuries exceptive the centuries are divisible by 400 so these ones in red you skip but the ones in blue you would keep and that is what now keeps our calendar in sync with what's actually happening in the natural world around us and these graphs show you the Julian calendar drift and the Gregorian calendar drifts out of alignment with the spring equinox and then jumps back and it drifts away and jumps back and that's what's happening with these these leap years okay ironically I need to keep an eye on the time so why is is all so hard to measure anyway well I've already described the fact that we really like order and we want to be able to measure things and see that there's a common pattern but there isn't always order in nature it reminds me of those little boxes that kids have to put the shapes and the right holes and in this case they don't fit so that's what's happening if you look at how a day is defined for instance if you if the earth starts in this position facing the Sun and it rotates around so it's rotating spinning on its axis and orbiting at the same time by the time it gets to position two you have the same stars that were over here that I would be visible from this position so this is a definition of the sidereal day whereas the solar day is the time that it takes to rotate that little bit further so that you are facing the Sun again so you have two definitions of a day so which do you want to use as a day and the same is true whether you are looking at the month let's see how does this play so if you're looking at the definition of a month it also has two definitions it has when it's sitting between the Earth and the Sun you get a new moon should move on maybe it's duck appears to be stuck and then as it rotates around once it's in the same position relative to the earth then that will give you side aerial month and then once it's in the same position relative to the Sun that will give you a solar month so with all of these things you have many different definitions to draw on and that was the same when I introduced tropical year and a side aerial year earlier so it depends which of these you want to use for your definition and that's why things are such a mess the last thing that I wanted to talk about while they still have time in the next 15 minutes is we've discussed all of the big items of time right so we started by talking about months and the lunar cycle we talked about the years now I want to talk about well all of those big cycles they're all based on something in nature so they were based on the Sun they were based on the moon I want to talk a little bit about smaller units of time where does an hour come from for instance and these are more artificial measures that we have created to be able to define smaller units of our of our day basically so when we talk about hours well it was the ancient Egyptians who first decided to split a day into 12 hours they decided to split it into 10 hours and plus two Twilight hours Twilight in the morning Twilight in the evening so that gave you 12 hours and they were unequal hours because we know if we live away from the equator like we do here then in the summer our daylight hours are daylight the length of daylight is longer than in the winter so because Egyptians only counted hours during the daylight the length of the hours changed throughout the year you would have long hours in the summer and short hours in the winter so and this was totally normal for people they didn't mind they they thought this was a more productive way to use the day because it told them what proportion of the day that they had available to them to use so to them it was logical even when the the first watches and clocks were designed people would reset their clock to match unequal hours because that's what they wanted to know and for us that's a really sort of different way of thinking now hard to understand so they didn't count any time during the night time but it was the ancient Greek astronomers wanted to be able to do astronomy at night so they were the first ones to also split the night time into twelve hours and it was astronomers also who were the first ones to use equal hours because they wanted to know exactly what time something would reappear in the sky so equal hours were more important for astronomers the first types of devices for measuring time were Sun dials but the first sundial wasn't called a sundial it was called a shadow stick this is an ancient Egyptian shadow stick it didn't really give you an indication of hours it gave you it more of an indication of how much of the day had passed and because it's a stick like this and you look at the length of shadow on the stick this is where the English phrase the length of time comes from because you would have a look at the length of time you had left of your daylight and it was a lot later actually that Sun dials were invented Sun dials were invented in clocks were invented later in the northern hemisphere and clocks were based on the direction that the shadow moves on a sundial and that's why where we get the worm the term clockwise and the direction clockwise from because the clockwise direction followed the sundial direction so had Sun dials and clocks been invented in the southern hemisphere then clockwise would also be anti-clockwise not to confuse anyone there mmm okay so Sun dials no good at night time Sun dials probably no good in this part of the world where it's very rarely sunny so the other inventions that you get during this time are water clocks so people had to have a good knowledge of physics and candles or incense the first ever alarm clock was a candle with a pin stuck in the side so when the candle melted the pin would drop into a metal tray and that would wake you up and incense clocks were quite interesting you even got ones that had a different aroma at different times so you could tell the time just by smelling at this point so there's some very nice inventions when clocks were were first mechanical clocks were first invented there were the people didn't have them in the homes people would have the mainly in churches there would be one per village so you didn't know the time personally but you would have to go out into the village and they didn't have dials on them in fact people they just sounded the time via Bell and the word for clock comes from the german word glocca which means bell because that's what they did they sounded the hours people wanted to know the hours but they didn't have so much interest in time in between hours so that's where the word clock comes from and it's not until a hundred years later that you see the development of mechanical clocks as we think of them now with their dials on and in fact the first dial clocks had the full 24 hours around them rather than the 12-hour ones that we used to now ah so that was my question there was another question people often say well why are there 60 minutes in an hour and 60 seconds in a minute well actually this comes from mathematical convention I told you how Romans like the number 10 because you can count 10 very easily well the Babylonians and the Sumerians really like the number 60 and they used the number 60 in their sexagesimal system they used to count differently to us so they would count the number of bits of your finger so on one finger I have three segments and I have four fingers with three segments on on this hand so that gives me 12 and then I can do multiplication I can do 12 times 1 2 3 4 5 and I get 60 so they use this system for counting and 60 is a very good number if you want to divide through and not have any fractions so it has a lot of factors so mathematically the number 60 is very convenient at this point in time they didn't have they didn't have knowledge of fractions so they wanted to pick a large number that was easily divisible so they could always work in whole numbers when splitting things up so that's where the 60 comes from and they were also the first people to to split a circle into 360 degrees for the same reasons in okay so I want to spend the last 10 minutes of my lecture just bringing you up to date basically so we've gone right from the past and we're sort of getting there we're in the 1700s now the last thing that I want to talk about is about transportation navigation and time because these things have all affected the development of time so in the 1700s there was this was a period where you were getting a lot more trade you were getting a lot more transport across the globe and you were getting a lot of shipping disasters during this time there were huge disasters and in in Britain as well as in many other countries a reward was offered for somebody who could invent a safe method for navigation and this really promoted the development of clocks and watches and timekeepers in general the the way that they used to the methods that they used to use for sailing and navigating was dead reckoning so this was if you if you knew where you wanted to go measuring your latitude how north or south you are is very easy to do by the Sun or by the pole star so you could do that and you would travel north or south mainly north and then you would use a compass to try and travel directly in a straight line east or west to your destination point the problem with doing that is that people knew that there was only one route you could take so it was very easy to get hijacked by whoever else is after whatever it is you're carrying so this was a big problem and navigation was dangerous in this method anyway because to use dead reckoning you also needed to make estimates about how fast you were traveling so people would tie knots into rope and let the rope out of the end of the boat and time a certain amount of time and see how many knots had slipped through your fingers hence where we get the term the unit for measuring knots from that was actually very difficult to do because of surface currents and things like that and also using a compass to judge your direction east/west is not very good either because this actually varies throughout the world depending on where you are so measuring latitude was something that was very easy to do and as I say you can use the elevation of the Sun above the horizon to do this or the Polestar and things like that and it's just a question of geometry but when it turns when you want to calculate your longitude your distance east or west of something then you really need a good time piece to be able to do that and this period there wasn't anything that was really reliable so if you have a timepiece and you set it to noon when you leave Maastricht and you travel far away if you measure what time noon went there Berlin Suns highest in the sky when you measure that time at your new location if you know the difference in time between your noon that you're viewing where you are and what it was back home then you can work out how far around each the West you've traveled from that position so that's why they really needed a good time piece and that's one of the promoting factors that took place during the seven 1700s in the other way railways and the development of railway transport across countries especially America in Canada big countries really changed how we perceive time before the development of the railways in the 1800s actually every city kept its own local time so you could go from from here to here 'ln and here then would have a different time here from valkenburg or valkenburg would have a different time because everybody was measuring the time relative to the position of the Sun so it was really complicated but didn't really matter before the railways because it took me so long to walk anywhere that by the time I got there didn't matter that the time was different whereas when the railways developed people for the first time were able to travel long distances within a short period of time so there were noticing these differences more and more and what was worse if you especially in big countries like America if you got to the train station the time of the train you were catching was dependent on the station or the company of the train that the train you were catching was from so if I were so if I was in New York and I was catching a train from Columbus I would have to know what where the train from Columbus came from if it came from Columbus it would be on Columbus time and the time I was catching it in New York I would have to recalculate what the Columbus time was relative to the time that I am basically this doesn't make any sense that's that's how it felt it didn't make any sense you would go to a train station there would be five different clocks on the wall if you were catching the train from Columbus you would have to know what time on Columbus time it was going to be at your train station and then work out what it meant to you so this was a complete mess so in the late 1800s in 1884 1887 that period Standard Time was introduced so that's when the world was basically split up into fifteen degree segments they would all have one set hourly time so that was the development of Standard Time and that's pretty much how it remains to this day it can be a little bit more complicated depending on the borders that countries have etc the the other complication to Standard Time was that before the wall an idea was introduced to have daylight savings time because it would allow people in faraway from the equator like we are to enjoy more sunlight hours in the summer but it wasn't an idea that took off and it didn't take off until the Germans wanted to save money save fuel during the war time to put towards the war effort so they decided they were the first to decide to introduce daylight savings time but this adds complication to standard time because some countries use it some countries don't in America there's a state that does have it but there are areas and reserves within the state that don't have it and all countries choose to implement standard time on different dates and sorry daylight savings time on different dates so everything comes in and out of alignment again just to make it more complicated the war also had other impacts on time if you if if you've got jeans or trousers they often have like especially in men's trousers in the pocket they have another little pocket in there that pocket was designed for wristwatches because before the First World War it was very uncool for men to wear wristwatches it wasn't until during the first world war that people they couldn't be rummaging around in their pockets to find the time so they had to have it in a more convenient place and then it became more acceptable for men to wear wristwatches so that was the other implication of the war and to finish I just want to talk about the technology that has moved on to today so now our technology in measuring time has become better and better so we have quartz clocks and quartz watches quartz is a crystal and this crystal has the it's called piezoelectric properties so if you run a current through this material the crystal will vibrate at a given frequency and that given frequency is the frequency that is used to control your timepiece so that was one of the first developments in these types of watches in the 20s and digital clocks as well rely on microchips and transistors to do frequency division and counting and mathematics based on either if you've got a main signal from the wall and an AC signal and the final things to talk about is what we are using today today the the definition of a second is very different from when it was first defined so we've talked about the length of a day and the the average solar day we've we've talked about already and that is how a second was defined it was defined taking the length of a mean solar day and you divide that by the 24 hours then the 60 minutes then the 60 seconds and that gives you your definition of a second the problem with that as well as it's very difficult to measure what a solar day is the solar day actually shifts at different times of the year so the orbit of the earth around the Sun isn't a circle it's actually an ellipse and the the earth travels faster when it's closest to the to the Sun than when it's further away and also the tilt of the earth relative to its orbit also makes a difference to how long the solar day is throughout a year so this measurement for one second isn't something that can be easily measured and it's not something that's very consistent so in the 1960s scientists wanted to have a set way that a second could be defined and measured everywhere in the world so that we could have consistency between countries and we could have consistencies with measurements and it was then that they decided to choose the vibrations of a cesium atom once it's in a microwave as the definition of a second and this gives you a very accurate and reliable method to use and it's this definition and it's these it's this technique that is used in atomic clocks and that's what we use today to control all of our timepieces and we set all of the rest of our quartz watches to be consistent with what the atomic clocks are saying and if it wasn't for these atomic clocks we wouldn't have the GPS navigation that we have today so we've sort of gone from having navigation at sea promoting the development of of clocks and watches too now we have an atomic clock and it's helping us to navigate once again so hopefully you see in this talk that all of this history has not only and development has not only letters to know when we are but we now know where we are because we know when we are so I'm kind of hoping that this talk has answered some of your questions about the development of time perhaps if anyone says that they want to have a meeting with you next Monday next week on Monday 4 o'clock you'll think twice about oh well where did Monday come from and where did these hours come from and where did the the week develop from and perhaps you all have I don't know developed an appreciation from all of these theologians and emperors and kings and Pope's and astronomers and mathematicians whose influence have led us to to have these forms of time and divisions of time that we take for granted every day thank you very much

Channel: School of Business and Economics

Views: 103,715

Rating: 4.8009291 out of 5

Keywords: History of Time and Calendar, Maastricht University, Donna Carroll, School of Business and Economics, Time

Id: OaYMK2n9Aow

Length: 58min 19sec (3499 seconds)

Published: Thu Mar 24 2016