Editing 1935: 2018
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{{comic | {{comic | ||
| number = 1935 | | number = 1935 | ||
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==Explanation== | ==Explanation== | ||
− | In this, the first of two [[:Category:New Year|New Year comics]] in a row, [[Megan]] wonders | + | In this, the first of two [[:Category:New Year|New Year comics]] in a row, [[Megan]] wonders if 2018 will be a {{w|Leap year|leap year}}. [[Cueball]] thinks 2018 will not be a leap year, and Megan responds that she "doubts anyone knows at this point." This appears to be a jab at the complexity of the leap year system. As Cueball says, leap years occur every four years (though there are a few exceptions), adding an extra day to account for the fact that Earth takes a bit longer than 365 days to orbit the Sun. Therefore, most years that are a multiple of four are leap years. As Megan says, this is easy for odd-numbered years, since no odd numbers are divisible by four. However, for even-numbered years, it isn't always obvious. |
− | The last panel expresses a misunderstanding of modern public-key {{w|Cryptography|cryptography}}, which relies on the fact that it is difficult to factorize large numbers. Megan is applying this concept to the year, claiming that it is hard to determine whether or not | + | The last panel expresses a misunderstanding of modern public-key {{w|Cryptography|cryptography}}, which relies on the fact that it is difficult to factorize large numbers. Megan is applying this concept to the year, claiming that it is hard to determine whether or not 2018 is a multiple of four and hence is a leap year. In reality, factorization is not needed here, since we already know the factor, which is four. Megan states that if it were possible to factor large numbers with a calculator, modern cryptography would collapse. While true, it is only true for truly large numbers (hundreds of digits), and no factorization is needed in this case. |
− | At the end of the strip, Megan hopes the answer can be {{w|Brute-force attack|brute-forced}} by February. Brute force is a method of breaking cryptography by trying every possible option until one works. This is misdirection upon misdirection, in that | + | At the end of the strip, Megan hopes the answer can be {{w|Brute-force attack|brute-forced}} by February. Brute force is a method of breaking cryptography by trying every possible option until one works. This is a misdirection upon misdirection, in that even if we needed to factorize 2018 (which we don't), the simplest brute forcing algorithm would only need to try 14 numbers - each prime from 2 to 43 (the square root of 2018 is closest to 44). In cryptography, the algorithms use numbers much, much bigger than 2018 -- on the order of hundreds (or even thousands) of digits. |
− | The title text refers to calculating which day {{w|Christmas}} will fall on. | + | The title text refers to calculating which day {{w|Christmas}} will fall on. Given that it always falls on December 25th (in western countries), there is nothing to calculate. They could mean which day of the week, so it's either the 359th or the 360th (leap years) day of the year and the day of the week may differ. This is a reference to Easter whose date jumps from year to year according to a complicated algorithm that most people don't know. The changing date of Easter was recently included in [[1930: Calendar Facts]]. |
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==Transcript== | ==Transcript== | ||
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*Since 100 is divisible by 4, only the last two digits of a number are needed to determine if that number is divisible by 4. So to determine if 2018 is divisible by 4, we only need to check whether 18 is divisible by 4, which is easy. | *Since 100 is divisible by 4, only the last two digits of a number are needed to determine if that number is divisible by 4. So to determine if 2018 is divisible by 4, we only need to check whether 18 is divisible by 4, which is easy. | ||
− | *2018 is not divisible by 4, so the year | + | *2018 is not divisible by 4, so the year is not a leap year. 2016 and 2020 are leap years. Assuming your calendar is Gregorian! A year is roughly 365.2422 days long. (Actually, also the case if it is 2018 on the old Julian calendar. The century year rules for leap years are different on the Gregorian calendar from the Julian, but the non-century year rules are the same). |
− | *{{w|Eastern Christian Churches}} celebrate Christmas also on December 25 but | + | *{{w|Eastern Christian Churches}} celebrate Christmas also on December 25 but of the older Julian calendar, which currently corresponds to January 7 in the Gregorian calendar. |
− | *This is the third year in a row with New Year's comics with only the year used as the title | + | *This is the third year in a row with New Year's comics with only the year used as the title, before that there were two more comics with such titles, but those two (and thus the first three) were only released in the even years: [[998: 2012]] in 2012, [[1311: 2014]] in 2014, [[1624: 2016]] in 2016 and [[1779: 2017]] in 2017. |
+ | * XKCD comic number 2018 will occur sometime in 2018. So we will have a comic named 2018 and a comic numbered 2018 both in the year 2018. | ||
{{comic discussion}} | {{comic discussion}} | ||
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[[Category:Comics featuring Cueball]] | [[Category:Comics featuring Cueball]] | ||
[[Category:Comics sharing name|2017]] | [[Category:Comics sharing name|2017]] | ||
− | [[Category: | + | [[Category:Math]] |
− | [[Category: | + | [[Category:Time]] |
[[Category:Cryptography]] | [[Category:Cryptography]] |