Cosmology and astronomy
- Human evolution overview
- Understanding calendar notation
- Correction calendar notation
- Development of agriculture and writing
- Firestick farming in early Australia
- Collective learning
- Thomas Malthus and population growth
- Agriculture and human population
- Energy inputs for tilling a hectare of land
- Random predictions for 2060
Understanding calendar notation
Difference between BC, BCE, AD and CE. A little bit about the birth of Jesus as well. Created by Sal Khan.
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- Are there any modern calender systems in use that do not center around religious doctrine?
I've heard of the "world calender", but it's a bit of an esperanto situation.(12 votes)
- The simple answer is "no, not really". There are still some national calendars which still use other systems -- Taiwan uses years counted from the formation of the Republic of China in 1911, and Japan counts the year of the reign of the current emperor -- but in all cases these are used alongside (not instead of) the Gregorian calendar, which has rather become the de facto standard internationally.
Thinking historically, if you wish to number your years, then you have to have some basis for your numbering system. It makes the most sense to use a date which has great significance to many people, and major national or religious events are the obvious examples. Then, with increasing communication between regions and countries, the national bases for counting lost their significance, and it was really only the religious numbering systems which remained understandable and desirable by people of many different countries.
So most of the calendar systems in the world today are religious ones, with the few counter-examples being used only by one country.(11 votes)
- What type of calendar did the Egyptians use? and what did they base it on? Oh and the Romans too. Thanks!(7 votes)
- Prior the the roman take over of Egypt their calendar had 12 months of 30 days each, with an extra five days at the end of the year to bring the total number of days to 365. The months were divided into three weeks of ten days each.
The romans changed the calendar so that every 4 years there would be an extra day.(2 votes)
- So if the year now is CE 2012 and we are in the 21st century, if we were in the year CE 1, what century would we be in? We couldn't be in the 2nd century because there is no CE 0.(3 votes)
- You would be in the first century, or the first hundred years (which is a century).(17 votes)
- ok so if there wasn't the year zero, would that mean that the turn of the century was in 2001, and 2000 was still in the 20th century? I'm confused about that.(3 votes)
- The 20th century ended on December 31 2000 and the 21st century started January 1st 2001.
All of the millennium celebrations at the end of 1999 were a year too early.(10 votes)
- What does Common Era mean?(3 votes)
- One can also argue that Common Era refers to the fact that in the west (ie Europe and America) and much of the commercial world globally we COMMONLY use the birth of Christ as our starting point. In other words this is the Era (timescale) we commonly or normally use and understand.
You could start an "uncommon era" by choosing a different starting point which nobody would (yet) be used to seeing or using, but if it was powerful or logical or exciting enough then eventually that would become the standard.
Of course, then somebody would have to challenge the naming of UCE (UnCommon Era) and call it something like UTS (Useful TimeScale).(4 votes)
- At8:15, the video said that there is no year 0. Why is this?(2 votes)
- because since the dating system is based on the birth of christ, there's either the time before he was born or the time after. he could hardly take a whole year to exit his mum's womb. and since the original meaning is not "after his birth" but the "year of the lord", it would have been counted as the "first year of the lord" as in 1st year jesus exist.(1 vote)
- If we say Plato was born in 428 BCE, in which year would Plato say he was born?(2 votes)
- What's the difference between BC/AD and BCE/CE they both switch on the birth of christ. If scientists really wanted to choose a new date system, they should have made it so it switched on started on a non-religious date.(2 votes)
- I think BCE/CE is an attempt to remove Christ from being directly referred to. Remember, most of the world is not christian.(1 vote)
- Here's a calendar question...Is there a good explanation as to why there are 7 days in a week? Why not 5? We have 5 fingers on one hand. 5 divides evenly into 365 (the number of days in a year) and we could just say that each month has 6 weeks (6 x 5 =30). Doesn't 7 seem like an odd selection given the alternatives?(1 vote)
- The 7 day week dates back to the ancient Babylonians, who called every 7th day a holy day. Later, the 7-day week appeared in the Hebrew bible, with god resting on the 7th day, leading to a religious obligation to "rest" on the sabbath (sabbath =7th), as stated in the 10 commandments.
The lunar cycle divides pretty closely into 4 weeks, so that may have something to do with why the Babylonians went with 7 days in the first place.(3 votes)
- When did they decided that they would use the short form, B.C.E?(2 votes)
- since they noticed that "before common era" takes too long to type or write(1 vote)
This right here is a fresco by Raphael of Plato hanging out with his best student, Aristotle. And you may or may not know that these two fellows, along with Plato's teacher, Socrates, are considered the fathers of Western philosophy. But that's not what this video is about. This is actually just a small little video about different dates, or maybe a better way to think about it, different ways to specify dates or dating mechanisms. And so, if you were to look up Plato's birth, you might get either 428 or 427, but we'll go with 428. If you were to look up Plato's birth, you might see it written as 428 BC, or you might see it written as 428 BCE. And the natural question is, what's the difference here? They both have a BC, but this one has an E. It's the same year right now. And the answer is that these are referring to the exact same year in history, but the acronyms here do stand for different things. BC literally stands for Before Christ. So if the date is written 428 BC, the implication is that this is 428 years before the birth of Christ. We'll see in a second that that's not exactly right, but that's what the implication is. If someone writes BCE, they're saying something very different. The B still stands for before. But the CE, the C in CE does not stand for Christ anymore. It now stands for common. And so the CE part is Common Era. Even though it's not referring to Christ anymore-- and the intention here is so that it's less religious than the term "Before Christ"-- it's still putting an importance on Christ's birth, because it's saying that the common era is the time period after the birth of Christ, which we'll see in a second isn't exactly right. But there's essentially the same exact dating scheme. One not directly referring to Christ, one that is directly referring to Christ. Similarly, this right here is a painting of Christopher Columbus. And if you were to look up in history books, when was his first voyage and when did he first show up in the New World, finding an island in the Bahamas? You would see it written as either 1492 or AD 1492 or 1492 CE. And once again, these are all referring to the same year, just using different acronyms. One of them's a little bit more religious, or more directly refers to Christ. And one is a little less religious. So AD, some people think it refers to after death. It does not refer to after death, because if you think about it, if you have years before the birth of Christ, and if you started numbering after his death, how would you number the years during his life? So AD does not stand for after death. It stands for Anno Domini, which literally means, anno means year, and domini means lord, or the lord's. So it's the year of the Lord or the year of our Lord. So it's years since. And 1 Anno Domini would be the year of Jesus Christ's birth. So not after death. It stands for Anno Domini, but literally year of our Lord. So years since Jesus was born, with year one implicitly starting with his birth. And we'll see in a second that's not exactly right. CE stands for Common Era. Once again, 1 CE is the same thing as AD 1. Sometimes we now write, instead of writing AD 1492, we'll write 1492 AD, all referring to the exact same thing. Now, all of these things we refer to, when we say 428 BC it implies 428 years before the birth of Christ. 1492 AD, that's in the year of our Lord 1492, it implies 1492 years since the birth of Christ. But the reality is that we're not really quite sure when Christ was born. And so these aren't exactly. Columbus didn't sail across the Atlantic exactly 1492 years after the birth of Christ. Most historians put the birth of Christ at 7 to 2 BC or BCE, depending on how you want to view it. Remember BC is Before Christ, which is a little ironic, because we're talking about the actual birth of Christ. BCE is Before the Common Era. And they put his death at 30 to 36 AD, which is 30 to 36 in the year of our Lord, or-- that's what this stands for, Anno Domini-- or in the Common Era, CE. Now some people, they obviously don't like BC. They don't like the BC, AD naming mechanism, because it's explicitly referring to Christ in every year. It makes Christ the central figure in all of history. So they'll say that this is clearly too Christian. And they would prefer the situation, they would prefer the less Christian naming scheme where you use BCE and CE. But a lot of people would still say, hey, look you change. Well, you know, first of all, some Christians wouldn't like this that you removed the direct references to the birth of Christ, or being in the years since Christ's birth. But even here, and they'll say, you've removed it. But even here, some people would complain that although you've made the direct reference that this is saying Before the Common Era, and the Common Era, even though you've removed the direct reference, it still makes Christ's birth the central thing in all of history. But this is the convention whether people like it or not. In order to have the same reference point and it's too logistically difficult to switch it this time, everyone has essentially settled on this. It's really just a matter of letters of which naming scheme you pick. But the whole point of this video is that you don't get confused between BC and BCE. You don't think that AD stands for after death, it stands for Anno Domini, in the year the Lord, or the year of our Lord. And CE stands for Common Era. But this and this are referring to essentially the same count after Christ, after the birth of Christ, or this theoretical birth of Christ, which we don't really know when it actually happened. It probably did not happen at the beginning of 1 AD or 1 CE. And these two things also refer to the same direction in the timeline. One last thing I want to point out is that there is no year 0. So if you take either of these naming schemes, you have, so let's go very close to the year 1. So there's just some point, this theoretical birth of Christ, which was probably not the actual birth of Christ, but at that theoretical point-- so New Year's, so you have December 31 of the previous year, all of a sudden, now, you are on January 1 of 1 AD or CE, depending on how you want to refer to it. And the year before that was 1 BC or BCE, depending on how you want to refer to it. So there is no year 0 in this scheme. And then the last thing I want to emphasize-- and it might be obvious to you-- is the larger a number you have here, the further back you're going in time. Because this is saying how many years before this theoretical birth of Christ, and obviously larger numbers here, you have here, this is the further you're going off into the future. And if you wanted to figure out how many years passed between Plato's birth and Columbus sailing across the Atlantic to find the New World, you would say, well, look, it took 428 years to go from Plato's birth to this theoretical birth of Christ. And then you have another 1492 years to wait until Columbus gets his ship together. So the total number of years would be-- I'll do it right over here-- 428 years to get to Christ from Plato's birth, and then you have another 1492 years to wait for Columbus. So let's see, 8 plus 2, that is 10. As you can see, I just wanted to add a little arithmetic in this video. So 1 plus 2 plus 9 is 12. And then we have 9, 1 plus 4 plus 4. So 1,920 years between Plato's birth and Columbus sailing across the Atlantic.