Millennium and the Year 0
Date: 01/03/99 at 22:39:33 From: Katie Subject: Millennium I am doing a science project on when the new millennium really begins. I already know that it truly begins in the year 2001 because there was no zero year between B.C. and A.D. I was wondering if you knew why or could give me some sites about why the early mathematicians didn't let a whole year pass before naming it one. I would also appreciate any other information you could give me about my project. I have already looked it up under many different subjects in Encarta 98 and tried tons of different ways to get information on the Web, but I'm having trouble finding information. Thanks, Katie
Date: 01/04/99 at 08:47:26 From: Doctor Rick Subject: Re: Millennium Hi, Katie, welcome to Ask Dr. Math! Thanks for asking this question, it's a good one. To answer it, you will need to look at the history of the calendar, and the history of math. BC dates were not used in the BC era. BC means "before Christ"; that is, before the birth of Christ. Before he was born, people (even the relatively few people who were expecting his birth) did not know just when it would be, so they couldn't date their calendars that way! As a matter of fact, AD and BC were not invented until around AD 525, by Dionysius Exiguus. In AD 525, people in Europe didn't have a clear idea about negative numbers. In fact, it wasn't until 1657 that a mathematician (John Hudde) used a single variable to represent either a positive or a negative number. For all those years until 1657, positive and negative numbers were handled separately. Nobody drew a number line with positive numbers on one side, negative numbers on the other, and 0 in between. Let's get back to Dionysius. He identified the year 1 AD ("1 Anno Domini," the first year of the Lord) as the year that Christ was born (he was probably off by 4 to 6 years). The previous year was 1 BC, the first year "Before Christ." (I have not figured out why one abbreviation is in Latin while the other is in English.) Dionysius would not have thought of 1 BC as the year -1. He would not have thought of putting BC and AD together on a number line (timeline). BC and AD were two separate cases. To find the time between two AD dates, you would take their difference. To find the time between an AD date and a BC date, you would add them and subtract 1. This would not be seen as a problem. It's just the way they solved other kinds of problems (like quadratic equations, if you've seen them) - as a set of special cases. I have found some Web sites that can give you more information on the things I have said. Here is an interesting Web page about the origin of the calendar (see the section "Century and Millennium"): Larry Freeman's Calendar Origin Page http://ourworld.compuserve.com/homepages/Larry_Freeman/calendar.htm Here is another (see the section "The start of Anno Domini Dating"): Historical Ecclesiastical Calendar: Easter and its Relevance for Chronology http://ourworld.compuserve.com/homepages/khagen/Easter.html#AD Here is a Web page about the origin of negative numbers: Negative Numbers - Kevin Brown http://www.mathpages.com/home/kmath298.htm One of Jeff Miller's pages is my reference for John Hudde: Earliest Uses of Symbols for Variables http://jeff560.tripod.com/variables.html - Doctor Rick, The Math Forum http://mathforum.org/dr.math/
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