explain xkcd - User contributions [en]

1935: 2018

2017-12-30T08:55:15Z

FarmerBob:

{{comic
| number = 1935
| date = December 29, 2017
| title = 2018
| image = 2018.png
| titletext = We should really start calculating it earlier, but until the end of December we're always too busy trying to figure out which day Christmas will fall on.
}}

==Explanation==
{{incomplete|Anything missing? - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

In this [[:Category:New Year|New Year comic]], [[Megan]] is bizarrely incredulous about basic arithmetic. In fact 2018 is ''not'' a {{w|Leap year|leap year}}; it is easy to determine if 2018 is evenly divisible by 4 (it's not). For some reason, [[Cueball]] is easily swayed by her aggressively stupid statements.

Megan wonders if 2018 will be a 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 {{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 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 43 numbers - from 2 to square root of 2018 (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 of the week Christmas will fall on. Given that any calendar app will easily tell you, this is not a difficult thing to calculate. Also it always falls on December 25th, and not like, for instance, Easter which date jumps from year to year. But nevertheless December 25th is either the 359th or the 360th (leap years) day of the year and so the day of the week could be different.

==Transcript==

:[Megan is walking.]
:Megan: I wonder if 2018 will be a leap year.

:[Now it turns out that Cueball walks behind Megan.]
:Cueball: ...it won't be, right?
:Megan: I doubt anyone knows at this point.

:[Same scene in a frame-less panel.]
:Cueball: No, it's definitely not. Leap years are divisible by 4.
:Megan: Right, and for odd numbers, that's easy.
:Megan: But 2018 is even.
:Megan: 50/50 chance.

:[Zoomed-out view with both walking in silhouette on a dark slightly curved ground.]
:Cueball: I can settle this with a calculator.
:Megan: No way. If it were easy to factor large numbers like that, modern cryptography would collapse.
:Cueball: I see.
:Megan: I just hope we manage to brute-force it by February.

==Trivia==
*Released on Friday, December 29, this is the last comic of 2017. The next scheduled comic will be on New Year's Day of 2018.

*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.

{{comic discussion}}

[[Category:New Year]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Cueball]]
[[Category:Comics sharing name|2017]]
[[Category:Math]]
[[Category:Time]]
[[Category:Cryptography]]

1935: 2018

2017-12-30T08:52:58Z

FarmerBob:

{{comic
| number = 1935
| date = December 29, 2017
| title = 2018
| image = 2018.png
| titletext = We should really start calculating it earlier, but until the end of December we're always too busy trying to figure out which day Christmas will fall on.
}}

==Explanation==
{{incomplete|Anything missing? - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

In this [[:Category:New Year|New Year comic]], [[Megan]] is bizarrely incredulous about basic arithmetic. In fact 2018 is ''not'' a {{w|Leap year|leap year}}; it is easy to determine if 2018 is evenly divisible by 4 (it's not). For some reason, [[Cueball]] is easily swayed by her aggressively stupid statements.

Megan wonders if 2018 will be a 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 {{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 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 43 numbers - from 2 to square root of 2018 (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 of the week Christmas will fall on. Given that any calendar app will easily tell you, this is not a difficult thing to calculate. Also it always falls on December 25th, and not like, for instance, Easter which date jumps from year to year. But nevertheless December 25th is either the 359th or the 360th (leap years) day of the year and so the day of the week could be different.

==Transcript==

:[Megan is walking.]
:Megan: I wonder if 2018 will be a leap year.

:[Now it turns out that Cueball walks behind Megan.]
:Cueball: ...it won't be, right?
:Megan: I doubt anyone knows at this point.

:[Same scene in a frame-less panel.]
:Cueball: No, it's definitely not. Leap years are divisible by 4.
:Megan: Right, and for odd numbers, that's easy.
:Megan: But 2018 is even.
:Megan: 50/50 chance.

:[Zoomed-out view with both walking in silhouette on a dark slightly curved ground.]
:Cueball: I can settle this with a calculator.
:Megan: No way. If it were easy to factor large numbers like that, modern cryptography would collapse.
:Cueball: I see.
:Megan: I just hope we manage to brute-force it by February.

==Trivia==
*Released on Friday, December 29, this is the last comic of 2017. The next scheduled comic will be on New Year's Day of 2018.

*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.

{{comic discussion}}

[[Category:New Year]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Cueball]]
[[Category:Comics sharing name|2017]]
[[Category:Math]]
[[Category:Time]]
[[Category:Cryptography]]

1935: 2018

2017-12-30T08:50:34Z

FarmerBob:

{{comic
| number = 1935
| date = December 29, 2017
| title = 2018
| image = 2018.png
| titletext = We should really start calculating it earlier, but until the end of December we're always too busy trying to figure out which day Christmas will fall on.
}}

==Explanation==
{{incomplete|Anything missing? - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

In this [[:Category:New Year|New Year comic]], [[Megan]] is bizarrely incredulous about basic arithmetic. In fact 2018 is ''not'' a {{w|Leap year|leap year}}; it is easy to determine if 2018 is evenly divisible by 4 (it's not). For some reason, [[Cueball]] is easily swayed by her aggressively stupid statements.

Megan wonders if 2018 will be a 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 {{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 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 43 numbers -- from 2 to square root of 2018 (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 of the week Christmas will fall on. Given that any calendar app will easily tell you, this is not a difficult thing to calculate. Also it always falls on December 25th, and not like, for instance, Easter which date jumps from year to year. But nevertheless December 25th is either the 359th or the 360th (leap years) day of the year and so the day of the week could be different.

==Transcript==

:[Megan is walking.]
:Megan: I wonder if 2018 will be a leap year.

:[Now it turns out that Cueball walks behind Megan.]
:Cueball: ...it won't be, right?
:Megan: I doubt anyone knows at this point.

:[Same scene in a frame-less panel.]
:Cueball: No, it's definitely not. Leap years are divisible by 4.
:Megan: Right, and for odd numbers, that's easy.
:Megan: But 2018 is even.
:Megan: 50/50 chance.

:[Zoomed-out view with both walking in silhouette on a dark slightly curved ground.]
:Cueball: I can settle this with a calculator.
:Megan: No way. If it were easy to factor large numbers like that, modern cryptography would collapse.
:Cueball: I see.
:Megan: I just hope we manage to brute-force it by February.

==Trivia==
*Released on Friday, December 29, this is the last comic of 2017. The next scheduled comic will be on New Year's Day of 2018.

*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.

{{comic discussion}}

[[Category:New Year]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Cueball]]
[[Category:Comics sharing name|2017]]
[[Category:Math]]
[[Category:Time]]
[[Category:Cryptography]]

1935: 2018

2017-12-30T08:27:18Z

FarmerBob:

{{comic
| number = 1935
| date = December 29, 2017
| title = 2018
| image = 2018.png
| titletext = We should really start calculating it earlier, but until the end of December we're always too busy trying to figure out which day Christmas will fall on.
}}

==Explanation==
{{incomplete|Anything missing? - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

In this [[:Category:New Year|New Year comic]], [[Megan]] is bizarrely incredulous about basic arithmetic. In fact 2018 is ''not'' a {{w|Leap year|leap year}}; it is easy to determine if 2018 is evenly divisible by 4 (it's not). For some reason, [[Cueball]] is easily swayed by her aggressively stupid statements.

Megan wonders if 2018 will be a 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 {{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, no factorization is needed in this case. In fact, public key cryptography relies on the fact that checking that a number is a factor of another number is a fast operation.

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 43 numbers -- from 2 to square root of 2018 (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 of the week Christmas will fall on. Given that any calendar app will easily tell you, this is not a difficult thing to calculate. Also it always falls on December 25th, and not like, for instance, Easter which date jumps from year to year. But nevertheless December 25th is either the 359th or the 360th (leap years) day of the year and so the day of the week could be different.

==Transcript==

:[Megan is walking.]
:Megan: I wonder if 2018 will be a leap year.

:[Now it turns out that Cueball walks behind Megan.]
:Cueball: ...it won't be, right?
:Megan: I doubt anyone knows at this point.

:[Same scene in a frame-less panel.]
:Cueball: No, it's definitely not. Leap years are divisible by 4.
:Megan: Right, and for odd numbers, that's easy.
:Megan: But 2018 is even.
:Megan: 50/50 chance.

:[Zoomed-out view with both walking in silhouette on a dark slightly curved ground.]
:Cueball: I can settle this with a calculator.
:Megan: No way. If it were easy to factor large numbers like that, modern cryptography would collapse.
:Cueball: I see.
:Megan: I just hope we manage to brute-force it by February.

==Trivia==
*Released on Friday, December 29, this is the last comic of 2017. The next scheduled comic will be on New Year's Day of 2018.

*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.

{{comic discussion}}

[[Category:New Year]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Cueball]]
[[Category:Comics sharing name|2017]]
[[Category:Math]]
[[Category:Time]]
[[Category:Cryptography]]

1935: 2018

2017-12-30T08:21:44Z

FarmerBob: Clarify that no factorization is needed to determine the leap year, since the factor (4) is already known.

{{comic
| number = 1935
| date = December 29, 2017
| title = 2018
| image = 2018.png
| titletext = We should really start calculating it earlier, but until the end of December we're always too busy trying to figure out which day Christmas will fall on.
}}

==Explanation==
{{incomplete|Anything missing? - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

In this [[:Category:New Year|New Year comic]], [[Megan]] is bizarrely incredulous about basic arithmetic. In fact 2018 is ''not'' a {{w|Leap year|leap year}}; it is easy to determine if 2018 is evenly divisible by 4 (it's not). For some reason, [[Cueball]] is easily swayed by her aggressively stupid statements.

Megan wonders if 2018 will be a 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 {{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, no factorization is needed in this case. In fact, it is important for assymetric that checking if a number is a factor of another number is a fast operation.

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 43 numbers -- from 2 to square root of 2018 (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 of the week Christmas will fall on. Given that any calendar app will easily tell you, this is not a difficult thing to calculate. Also it always falls on December 25th, and not like, for instance, Easter which date jumps from year to year. But nevertheless December 25th is either the 359th or the 360th (leap years) day of the year and so the day of the week could be different.

==Transcript==

:[Megan is walking.]
:Megan: I wonder if 2018 will be a leap year.

:[Now it turns out that Cueball walks behind Megan.]
:Cueball: ...it won't be, right?
:Megan: I doubt anyone knows at this point.

:[Same scene in a frame-less panel.]
:Cueball: No, it's definitely not. Leap years are divisible by 4.
:Megan: Right, and for odd numbers, that's easy.
:Megan: But 2018 is even.
:Megan: 50/50 chance.

:[Zoomed-out view with both walking in silhouette on a dark slightly curved ground.]
:Cueball: I can settle this with a calculator.
:Megan: No way. If it were easy to factor large numbers like that, modern cryptography would collapse.
:Cueball: I see.
:Megan: I just hope we manage to brute-force it by February.

==Trivia==
*Released on Friday, December 29, this is the last comic of 2017. The next scheduled comic will be on New Year's Day of 2018.

*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.

{{comic discussion}}

[[Category:New Year]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Cueball]]
[[Category:Comics sharing name|2017]]
[[Category:Math]]
[[Category:Time]]
[[Category:Cryptography]]