explain xkcd - User contributions [en]

516: Wood Chips

2017-11-23T03:37:57Z

108.162.221.148: /* Explanation */ Seriously? Medieval is old, but not THAT old.

{{comic
| number = 516
| date = December 12, 2008
| title = Wood Chips
| image = wood_chips.png
| titletext = You didn't run a chemical analysis against the Shroud of Turin? Man, all that work for NOTHING.
}}

==Explanation==
[[Cueball]] has tried to play an elaborate hoax on a woman involving wood chips that match the composition of the wood used to build a 19th-century ghost ship called the {{w|Mary Celeste}}. Unfortunately, the woman has done the sensible, reasonable thing and thrown them out instead of checking to see if they belong to a ghost ship, whose wood chips or what-have-you would probably not have found their way to the hallway. This causes Cueball to realize that he needs to rethink the complicated way in which he creates hoaxes, because the people he is trying to trick do not follow through with his elaborate plans.

The title text suggests that he also set up some kind of chemical match with the {{w|Shroud of Turin}}. The Shroud of Turin is a famous artifact, said by some to have been used as Jesus's burial cloth, containing the ghostly image of a face.
A chemical analysis was performed on it in the late 1980s, which appeared to prove the cloth '''was''' medieval in origin (i.e. not old enough to have been used by Jesus); however, not everyone has fully accepted this finding.

==Transcript==
:[Cueball leans on desk; Woman sits behind desk.]

:Cueball: Did you ever figure out those mysterious woodchips?
:Woman: The ones in the hallway? No.
:Cueball: You didn't suspect that they matched the timber used in 1861 to build the "ghost ship" Mary Celeste, prompting you to send them to a lab for analysis, the results of which raised new and stranger questions?
:Woman: No, I threw them out. Why?

:My hoaxes need to get a lot less subtle.

{{comic discussion}}
[[Category:Comics featuring Cueball]]

Talk:1728: Cron Mail

2016-09-04T10:25:10Z

108.162.221.148:

I think the "MAILTO" variable in "/etc/crontab" is meant, so only only cron-mails would go to this address, not all mails for the user

[[User:Rincewind|Rincewind]] ([[User talk:Rincewind|talk]]) 13:09, 2 September 2016 (UTC)

The huge question is whether adding an email message to crontab would result in cron producing even more mail - or whether it would cause cron to fail in some way. The latter would do damage by killing some (possibly critical) cron tasks - the former could rapidly fill up the hard drive with an exponentially-growing crontab. An intermediate situation would be that cron simply ignores the junk and continues to function as before - in which case Cueball's change will have little practical impact on disk space consumption - but probably gradually slow cron's crontab parser to a crawl, which would also have rather severe effects. On most Linux setups, the mail directories are on a different partition to /etc. There is often very little spare space on the partition with /etc on it - so it's likely that Cueball's change will eventually do terrible damage in that case too. [[Special:Contributions/162.158.69.98|162.158.69.98]] 14:42, 2 September 2016 (UTC)
:On my Mint/Ubuntu/Debian-based Linux system, adding junk to /etc/crontab put a message is /var/log/syslog about "cron[1495]: (*system*) ERROR (Syntax error, this crontab file will be ignored)". So it looks like appending garbage to the crontab will just break cron entirely (or at least those handled by /etc/crontab; it may be private cron and /etc/cron.d/* jobs may continue to run, but cron.hourly, cron.daily, and cron.weekly jobs on my system are initiated through /etc/crontab so they would not run with a broken /etc/crontab). I don't know if other non-Debian distributions have a cron that behaves differently, however. [[User:N0lqu|-boB]] ([[User talk:N0lqu|talk]]) 15:18, 2 September 2016 (UTC)
:Seems like it wouldn't break the existing stuff, they'd still get run and then cron would start parsing the noise and complaining - the "intermediate" situation, though the "export MAILTO" seems wrong. If Cueball did it in his .bashrc, it might get into some of *his* cron jobs but unless it's in /etc/crontab (and there, no "export" is needed/used), it wouldn't matter. His jobs probably wouldn't have rights to write to /etc/crontab either. [[Special:Contributions/173.245.48.73|173.245.48.73]] 17:09, 2 September 2016 (UTC)
:Unfortunately this huge question is undecidable (by trivial reduction to halting problem) --[[Special:Contributions/172.68.54.126|172.68.54.126]] 08:10, 3 September 2016 (UTC)
The current explanation misses a part of the joke present in Cueball's last statement: he is considering the cron program to be somehow sentient and able to make a decision between sending the email (is it really important?) and its self-preservation by not trashing its own config file. He is thus daring cron to continue sending emails at the risk of 'self-destruction'.

- I also feel like the part of the joke is the cron has been sending him useless mail for 15 years. So now, he is sending cron useless mail

This states it can be run as infrequently as once a year, however by using February 29th, you can have it run once every 4 years (exc ever 100 inc every 400). But I think you might be able to get better by also setting it to run on a day of the week. e.g. February 29th, which is a Monday, which would then (after this year) not run for another 28 years, next running on February 29th, 2044.

Should that be noted in the article or is it a needless complication? (Also, I don't know what day of the week is what for this syntax).[[Special:Contributions/108.162.250.156|108.162.250.156]] 21:13, 2 September 2016 (UTC)
:That's interesting! but I don't think it's relevant to the joke. [[User:NotLock|NotLock]] ([[User talk:NotLock|talk]]) 23:13, 2 September 2016 (UTC)

:If you specify a day of week and a day of month it runs on both, so "11 59 29 2 1" would run at 11:59 on every Monday in February, as well as on February 29, not just on any February 29 that happened to be a Monday.--[[Special:Contributions/108.162.219.11|108.162.219.11]] 05:18, 3 September 2016 (UTC)

I'm hesitant to make substantial edits as a random non-registered IP address, but I do feel like this explanation could be improved if a lot of the technical details were removed. For example, the format of a crontab file and how it is parsed distracts a bit from the joke. For a non-technical audience, it would be much more concise to simply note that the file has a specific format, and piping random emails to it would probably break all of cron. In my opinion, the current explanation loses the forest for the trees. For me, the key part of the joke is Cueball doesn't know cron, Ponytail explains it, Cueball conducts a response which is intuitive in the real world ("okay, cron, if you think it's that important then you deal with it!") which would be horrible in a computer. Ponytail's comment on it being harsh, and that it would accidentally solve the problem is the punchline. I think all the other technical details distracts from that simple explanation.
: I would agree. Understanding how exactly cron works isn't really necessary to understand the comic and its humor. Perhaps linking to some "cron for dummies" tutorial for those interested[[Special:Contributions/141.101.91.223|141.101.91.223]] 04:03, 3 September 2016 (UTC)

What exactly does "hardball" mean? Is it a US slang term or such?[[Special:Contributions/141.101.91.223|141.101.91.223]] 04:03, 3 September 2016 (UTC)
:"Playing hardball" is an idiom, meaning "to act strong & aggressive about an issue" [[Special:Contributions/108.162.245.114|108.162.245.114]] 05:23, 3 September 2016 (UTC)

With "YOUR MOVE, CRON." Cueball adapts a famous movie quote ("Your move, creep.") from Robocop (1987) as if he would strike back against "the machine" from a similar age (admitted, cron is slightly older, but then again Robocop also plays 20 minutes into the future). [[User:Renormalist|Renormalist]] ([[User talk:Renormalist|talk]]) 06:35, 3 September 2016 (UTC)

Yeah, useless crap. I have smartd on my harddrives and still don't get any warnings that they are about to fail. Well except for all the cron emails I have been ignoring for a decade.[[Special:Contributions/162.158.83.240|162.158.83.240]] 09:15, 3 September 2016 (UTC)

A few corrections: (1) Setting MAILTO=/etc/crontab only affect the system-wide crontab. User crontabs will continue to run as normal. Cueball's cronjob runs under his account (we know that because "he has mail") therefore nothing will change as far as he is concerned. (2) MAILTO appends to the named file, therefore the existing lines in /etc/crontab will not be deleted and will continue to run as normal - the worse that can happen is that new, spurious, cronjobs can be introduced (3) in most modern versions of cron, you can run use a /X syntax which will cause X-1 executions to be skipped (for example 20 10 2 1/5 * will run once every 5 years - assuming the system has not been rebooted in the interim) [[User:Sysin|Sysin]] ([[User talk:Sysin|talk]]) 11:28, 3 September 2016 (UTC)

I agree that the explanation is overly technical, especially considering this Wiki exists largely as a resource to laypeople. A succinct explanation of the joke (the crux of which being that Cueball is actively trying to threaten a computer program) would be preferential to passing off a man page as an ExplainXKCD article. Although linking to a more detailed breakdown of how Cron functions isn't a bad idea at all. This is a pretty good one http://www.unixgeeks.org/security/newbie/unix/cron-1.html

Talk:1728: Cron Mail

2016-09-04T10:22:48Z

108.162.221.148:

I think the "MAILTO" variable in "/etc/crontab" is meant, so only only cron-mails would go to this address, not all mails for the user

[[User:Rincewind|Rincewind]] ([[User talk:Rincewind|talk]]) 13:09, 2 September 2016 (UTC)

The huge question is whether adding an email message to crontab would result in cron producing even more mail - or whether it would cause cron to fail in some way. The latter would do damage by killing some (possibly critical) cron tasks - the former could rapidly fill up the hard drive with an exponentially-growing crontab. An intermediate situation would be that cron simply ignores the junk and continues to function as before - in which case Cueball's change will have little practical impact on disk space consumption - but probably gradually slow cron's crontab parser to a crawl, which would also have rather severe effects. On most Linux setups, the mail directories are on a different partition to /etc. There is often very little spare space on the partition with /etc on it - so it's likely that Cueball's change will eventually do terrible damage in that case too. [[Special:Contributions/162.158.69.98|162.158.69.98]] 14:42, 2 September 2016 (UTC)
:On my Mint/Ubuntu/Debian-based Linux system, adding junk to /etc/crontab put a message is /var/log/syslog about "cron[1495]: (*system*) ERROR (Syntax error, this crontab file will be ignored)". So it looks like appending garbage to the crontab will just break cron entirely (or at least those handled by /etc/crontab; it may be private cron and /etc/cron.d/* jobs may continue to run, but cron.hourly, cron.daily, and cron.weekly jobs on my system are initiated through /etc/crontab so they would not run with a broken /etc/crontab). I don't know if other non-Debian distributions have a cron that behaves differently, however. [[User:N0lqu|-boB]] ([[User talk:N0lqu|talk]]) 15:18, 2 September 2016 (UTC)
:Seems like it wouldn't break the existing stuff, they'd still get run and then cron would start parsing the noise and complaining - the "intermediate" situation, though the "export MAILTO" seems wrong. If Cueball did it in his .bashrc, it might get into some of *his* cron jobs but unless it's in /etc/crontab (and there, no "export" is needed/used), it wouldn't matter. His jobs probably wouldn't have rights to write to /etc/crontab either. [[Special:Contributions/173.245.48.73|173.245.48.73]] 17:09, 2 September 2016 (UTC)
:Unfortunately this huge question is undecidable (by trivial reduction to halting problem) --[[Special:Contributions/172.68.54.126|172.68.54.126]] 08:10, 3 September 2016 (UTC)
The current explanation misses a part of the joke present in Cueball's last statement: he is considering the cron program to be somehow sentient and able to make a decision between sending the email (is it really important?) and its self-preservation by not trashing its own config file. He is thus daring cron to continue sending emails at the risk of 'self-destruction'.

- I also feel like the part of the joke is the cron has been sending him useless mail for 15 years. So now, he is sending cron useless mail

This states it can be run as infrequently as once a year, however by using February 29th, you can have it run once every 4 years (exc ever 100 inc every 400). But I think you might be able to get better by also setting it to run on a day of the week. e.g. February 29th, which is a Monday, which would then (after this year) not run for another 28 years, next running on February 29th, 2044.

Should that be noted in the article or is it a needless complication? (Also, I don't know what day of the week is what for this syntax).[[Special:Contributions/108.162.250.156|108.162.250.156]] 21:13, 2 September 2016 (UTC)
:That's interesting! but I don't think it's relevant to the joke. [[User:NotLock|NotLock]] ([[User talk:NotLock|talk]]) 23:13, 2 September 2016 (UTC)

:If you specify a day of week and a day of month it runs on both, so "11 59 29 2 1" would run at 11:59 on every Monday in February, as well as on February 29, not just on any February 29 that happened to be a Monday.--[[Special:Contributions/108.162.219.11|108.162.219.11]] 05:18, 3 September 2016 (UTC)

I'm hesitant to make substantial edits as a random non-registered IP address, but I do feel like this explanation could be improved if a lot of the technical details were removed. For example, the format of a crontab file and how it is parsed distracts a bit from the joke. For a non-technical audience, it would be much more concise to simply note that the file has a specific format, and piping random emails to it would probably break all of cron. In my opinion, the current explanation loses the forest for the trees. For me, the key part of the joke is Cueball doesn't know cron, Ponytail explains it, Cueball conducts a response which is intuitive in the real world ("okay, cron, if you think it's that important then you deal with it!") which would be horrible in a computer. Ponytail's comment on it being harsh, and that it would accidentally solve the problem is the punchline. I think all the other technical details distracts from that simple explanation.
: I would agree. Understanding how exactly cron works isn't really necessary to understand the comic and its humor. Perhaps linking to some "cron for dummies" tutorial for those interested[[Special:Contributions/141.101.91.223|141.101.91.223]] 04:03, 3 September 2016 (UTC)

What exactly does "hardball" mean? Is it a US slang term or such?[[Special:Contributions/141.101.91.223|141.101.91.223]] 04:03, 3 September 2016 (UTC)
:"Playing hardball" is an idiom, meaning "to act strong & aggressive about an issue" [[Special:Contributions/108.162.245.114|108.162.245.114]] 05:23, 3 September 2016 (UTC)

With "YOUR MOVE, CRON." Cueball adapts a famous movie quote ("Your move, creep.") from Robocop (1987) as if he would strike back against "the machine" from a similar age (admitted, cron is slightly older, but then again Robocop also plays 20 minutes into the future). [[User:Renormalist|Renormalist]] ([[User talk:Renormalist|talk]]) 06:35, 3 September 2016 (UTC)

Yeah, useless crap. I have smartd on my harddrives and still don't get any warnings that they are about to fail. Well except for all the cron emails I have been ignoring for a decade.[[Special:Contributions/162.158.83.240|162.158.83.240]] 09:15, 3 September 2016 (UTC)

A few corrections: (1) Setting MAILTO=/etc/crontab only affect the system-wide crontab. User crontabs will continue to run as normal. Cueball's cronjob runs under his account (we know that because "he has mail") therefore nothing will change as far as he is concerned. (2) MAILTO appends to the named file, therefore the existing lines in /etc/crontab will not be deleted and will continue to run as normal - the worse that can happen is that new, spurious, cronjobs can be introduced (3) in most modern versions of cron, you can run use a /X syntax which will cause X-1 executions to be skipped (for example 20 10 2 1/5 * will run once every 5 years - assuming the system has not been rebooted in the interim) [[User:Sysin|Sysin]] ([[User talk:Sysin|talk]]) 11:28, 3 September 2016 (UTC)

I agree that the explanation is overly technical, especially considering this Wiki exists at least in part to explain the comic to a layperson. A succinct explanation of the joke (the crux of which being that Cueball is actively trying to threaten a computer program) would be preferential to passing off a man page as an ExplainXKCD article. Although linking to a more detailed breakdown of how Cron functions isn't a bad idea at all. This is a pretty good one http://www.unixgeeks.org/security/newbie/unix/cron-1.html

Talk:1728: Cron Mail

2016-09-04T09:57:05Z

108.162.221.148:

I think the "MAILTO" variable in "/etc/crontab" is meant, so only only cron-mails would go to this address, not all mails for the user

[[User:Rincewind|Rincewind]] ([[User talk:Rincewind|talk]]) 13:09, 2 September 2016 (UTC)

The huge question is whether adding an email message to crontab would result in cron producing even more mail - or whether it would cause cron to fail in some way. The latter would do damage by killing some (possibly critical) cron tasks - the former could rapidly fill up the hard drive with an exponentially-growing crontab. An intermediate situation would be that cron simply ignores the junk and continues to function as before - in which case Cueball's change will have little practical impact on disk space consumption - but probably gradually slow cron's crontab parser to a crawl, which would also have rather severe effects. On most Linux setups, the mail directories are on a different partition to /etc. There is often very little spare space on the partition with /etc on it - so it's likely that Cueball's change will eventually do terrible damage in that case too. [[Special:Contributions/162.158.69.98|162.158.69.98]] 14:42, 2 September 2016 (UTC)
:On my Mint/Ubuntu/Debian-based Linux system, adding junk to /etc/crontab put a message is /var/log/syslog about "cron[1495]: (*system*) ERROR (Syntax error, this crontab file will be ignored)". So it looks like appending garbage to the crontab will just break cron entirely (or at least those handled by /etc/crontab; it may be private cron and /etc/cron.d/* jobs may continue to run, but cron.hourly, cron.daily, and cron.weekly jobs on my system are initiated through /etc/crontab so they would not run with a broken /etc/crontab). I don't know if other non-Debian distributions have a cron that behaves differently, however. [[User:N0lqu|-boB]] ([[User talk:N0lqu|talk]]) 15:18, 2 September 2016 (UTC)
:Seems like it wouldn't break the existing stuff, they'd still get run and then cron would start parsing the noise and complaining - the "intermediate" situation, though the "export MAILTO" seems wrong. If Cueball did it in his .bashrc, it might get into some of *his* cron jobs but unless it's in /etc/crontab (and there, no "export" is needed/used), it wouldn't matter. His jobs probably wouldn't have rights to write to /etc/crontab either. [[Special:Contributions/173.245.48.73|173.245.48.73]] 17:09, 2 September 2016 (UTC)
:Unfortunately this huge question is undecidable (by trivial reduction to halting problem) --[[Special:Contributions/172.68.54.126|172.68.54.126]] 08:10, 3 September 2016 (UTC)
The current explanation misses a part of the joke present in Cueball's last statement: he is considering the cron program to be somehow sentient and able to make a decision between sending the email (is it really important?) and its self-preservation by not trashing its own config file. He is thus daring cron to continue sending emails at the risk of 'self-destruction'.

- I also feel like the part of the joke is the cron has been sending him useless mail for 15 years. So now, he is sending cron useless mail

This states it can be run as infrequently as once a year, however by using February 29th, you can have it run once every 4 years (exc ever 100 inc every 400). But I think you might be able to get better by also setting it to run on a day of the week. e.g. February 29th, which is a Monday, which would then (after this year) not run for another 28 years, next running on February 29th, 2044.

Should that be noted in the article or is it a needless complication? (Also, I don't know what day of the week is what for this syntax).[[Special:Contributions/108.162.250.156|108.162.250.156]] 21:13, 2 September 2016 (UTC)
:That's interesting! but I don't think it's relevant to the joke. [[User:NotLock|NotLock]] ([[User talk:NotLock|talk]]) 23:13, 2 September 2016 (UTC)

:If you specify a day of week and a day of month it runs on both, so "11 59 29 2 1" would run at 11:59 on every Monday in February, as well as on February 29, not just on any February 29 that happened to be a Monday.--[[Special:Contributions/108.162.219.11|108.162.219.11]] 05:18, 3 September 2016 (UTC)

I'm hesitant to make substantial edits as a random non-registered IP address, but I do feel like this explanation could be improved if a lot of the technical details were removed. For example, the format of a crontab file and how it is parsed distracts a bit from the joke. For a non-technical audience, it would be much more concise to simply note that the file has a specific format, and piping random emails to it would probably break all of cron. In my opinion, the current explanation loses the forest for the trees. For me, the key part of the joke is Cueball doesn't know cron, Ponytail explains it, Cueball conducts a response which is intuitive in the real world ("okay, cron, if you think it's that important then you deal with it!") which would be horrible in a computer. Ponytail's comment on it being harsh, and that it would accidentally solve the problem is the punchline. I think all the other technical details distracts from that simple explanation.
: I would agree. Understanding how exactly cron works isn't really necessary to understand the comic and its humor. Perhaps linking to some "cron for dummies" tutorial for those interested[[Special:Contributions/141.101.91.223|141.101.91.223]] 04:03, 3 September 2016 (UTC)

What exactly does "hardball" mean? Is it a US slang term or such?[[Special:Contributions/141.101.91.223|141.101.91.223]] 04:03, 3 September 2016 (UTC)
:"Playing hardball" is an idiom, meaning "to act strong & aggressive about an issue" [[Special:Contributions/108.162.245.114|108.162.245.114]] 05:23, 3 September 2016 (UTC)

With "YOUR MOVE, CRON." Cueball adapts a famous movie quote ("Your move, creep.") from Robocop (1987) as if he would strike back against "the machine" from a similar age (admitted, cron is slightly older, but then again Robocop also plays 20 minutes into the future). [[User:Renormalist|Renormalist]] ([[User talk:Renormalist|talk]]) 06:35, 3 September 2016 (UTC)

Yeah, useless crap. I have smartd on my harddrives and still don't get any warnings that they are about to fail. Well except for all the cron emails I have been ignoring for a decade.[[Special:Contributions/162.158.83.240|162.158.83.240]] 09:15, 3 September 2016 (UTC)

A few corrections: (1) Setting MAILTO=/etc/crontab only affect the system-wide crontab. User crontabs will continue to run as normal. Cueball's cronjob runs under his account (we know that because "he has mail") therefore nothing will change as far as he is concerned. (2) MAILTO appends to the named file, therefore the existing lines in /etc/crontab will not be deleted and will continue to run as normal - the worse that can happen is that new, spurious, cronjobs can be introduced (3) in most modern versions of cron, you can run use a /X syntax which will cause X-1 executions to be skipped (for example 20 10 2 1/5 * will run once every 5 years - assuming the system has not been rebooted in the interim) [[User:Sysin|Sysin]] ([[User talk:Sysin|talk]]) 11:28, 3 September 2016 (UTC)

I agree that the explanation is overly technical, kind of defeating the purpose of this entire Wiki. A succinct explanation of the joke (the crux of which being that Cueball is actively trying to threaten a computer program) would be preferential to passing off a man page as an ExplainXKCD article. Although linking to a more detailed breakdown of how Cron functions isn't a bad idea at all. This is a pretty good one http://www.unixgeeks.org/security/newbie/unix/cron-1.html

Talk:1728: Cron Mail

2016-09-04T09:43:58Z

108.162.221.148:

I think the "MAILTO" variable in "/etc/crontab" is meant, so only only cron-mails would go to this address, not all mails for the user

[[User:Rincewind|Rincewind]] ([[User talk:Rincewind|talk]]) 13:09, 2 September 2016 (UTC)

The huge question is whether adding an email message to crontab would result in cron producing even more mail - or whether it would cause cron to fail in some way. The latter would do damage by killing some (possibly critical) cron tasks - the former could rapidly fill up the hard drive with an exponentially-growing crontab. An intermediate situation would be that cron simply ignores the junk and continues to function as before - in which case Cueball's change will have little practical impact on disk space consumption - but probably gradually slow cron's crontab parser to a crawl, which would also have rather severe effects. On most Linux setups, the mail directories are on a different partition to /etc. There is often very little spare space on the partition with /etc on it - so it's likely that Cueball's change will eventually do terrible damage in that case too. [[Special:Contributions/162.158.69.98|162.158.69.98]] 14:42, 2 September 2016 (UTC)
:On my Mint/Ubuntu/Debian-based Linux system, adding junk to /etc/crontab put a message is /var/log/syslog about "cron[1495]: (*system*) ERROR (Syntax error, this crontab file will be ignored)". So it looks like appending garbage to the crontab will just break cron entirely (or at least those handled by /etc/crontab; it may be private cron and /etc/cron.d/* jobs may continue to run, but cron.hourly, cron.daily, and cron.weekly jobs on my system are initiated through /etc/crontab so they would not run with a broken /etc/crontab). I don't know if other non-Debian distributions have a cron that behaves differently, however. [[User:N0lqu|-boB]] ([[User talk:N0lqu|talk]]) 15:18, 2 September 2016 (UTC)
:Seems like it wouldn't break the existing stuff, they'd still get run and then cron would start parsing the noise and complaining - the "intermediate" situation, though the "export MAILTO" seems wrong. If Cueball did it in his .bashrc, it might get into some of *his* cron jobs but unless it's in /etc/crontab (and there, no "export" is needed/used), it wouldn't matter. His jobs probably wouldn't have rights to write to /etc/crontab either. [[Special:Contributions/173.245.48.73|173.245.48.73]] 17:09, 2 September 2016 (UTC)
:Unfortunately this huge question is undecidable (by trivial reduction to halting problem) --[[Special:Contributions/172.68.54.126|172.68.54.126]] 08:10, 3 September 2016 (UTC)
The current explanation misses a part of the joke present in Cueball's last statement: he is considering the cron program to be somehow sentient and able to make a decision between sending the email (is it really important?) and its self-preservation by not trashing its own config file. He is thus daring cron to continue sending emails at the risk of 'self-destruction'.

- I also feel like the part of the joke is the cron has been sending him useless mail for 15 years. So now, he is sending cron useless mail

This states it can be run as infrequently as once a year, however by using February 29th, you can have it run once every 4 years (exc ever 100 inc every 400). But I think you might be able to get better by also setting it to run on a day of the week. e.g. February 29th, which is a Monday, which would then (after this year) not run for another 28 years, next running on February 29th, 2044.

Should that be noted in the article or is it a needless complication? (Also, I don't know what day of the week is what for this syntax).[[Special:Contributions/108.162.250.156|108.162.250.156]] 21:13, 2 September 2016 (UTC)
:That's interesting! but I don't think it's relevant to the joke. [[User:NotLock|NotLock]] ([[User talk:NotLock|talk]]) 23:13, 2 September 2016 (UTC)

:If you specify a day of week and a day of month it runs on both, so "11 59 29 2 1" would run at 11:59 on every Monday in February, as well as on February 29, not just on any February 29 that happened to be a Monday.--[[Special:Contributions/108.162.219.11|108.162.219.11]] 05:18, 3 September 2016 (UTC)

I'm hesitant to make substantial edits as a random non-registered IP address, but I do feel like this explanation could be improved if a lot of the technical details were removed. For example, the format of a crontab file and how it is parsed distracts a bit from the joke. For a non-technical audience, it would be much more concise to simply note that the file has a specific format, and piping random emails to it would probably break all of cron. In my opinion, the current explanation loses the forest for the trees. For me, the key part of the joke is Cueball doesn't know cron, Ponytail explains it, Cueball conducts a response which is intuitive in the real world ("okay, cron, if you think it's that important then you deal with it!") which would be horrible in a computer. Ponytail's comment on it being harsh, and that it would accidentally solve the problem is the punchline. I think all the other technical details distracts from that simple explanation.
: I would agree. Understanding how exactly cron works isn't really necessary to understand the comic and its humor. Perhaps linking to some "cron for dummies" tutorial for those interested[[Special:Contributions/141.101.91.223|141.101.91.223]] 04:03, 3 September 2016 (UTC)

What exactly does "hardball" mean? Is it a US slang term or such?[[Special:Contributions/141.101.91.223|141.101.91.223]] 04:03, 3 September 2016 (UTC)
:"Playing hardball" is an idiom, meaning "to act strong & aggressive about an issue" [[Special:Contributions/108.162.245.114|108.162.245.114]] 05:23, 3 September 2016 (UTC)

With "YOUR MOVE, CRON." Cueball adapts a famous movie quote ("Your move, creep.") from Robocop (1987) as if he would strike back against "the machine" from a similar age (admitted, cron is slightly older, but then again Robocop also plays 20 minutes into the future). [[User:Renormalist|Renormalist]] ([[User talk:Renormalist|talk]]) 06:35, 3 September 2016 (UTC)

Yeah, useless crap. I have smartd on my harddrives and still don't get any warnings that they are about to fail. Well except for all the cron emails I have been ignoring for a decade.[[Special:Contributions/162.158.83.240|162.158.83.240]] 09:15, 3 September 2016 (UTC)

A few corrections: (1) Setting MAILTO=/etc/crontab only affect the system-wide crontab. User crontabs will continue to run as normal. Cueball's cronjob runs under his account (we know that because "he has mail") therefore nothing will change as far as he is concerned. (2) MAILTO appends to the named file, therefore the existing lines in /etc/crontab will not be deleted and will continue to run as normal - the worse that can happen is that new, spurious, cronjobs can be introduced (3) in most modern versions of cron, you can run use a /X syntax which will cause X-1 executions to be skipped (for example 20 10 2 1/5 * will run once every 5 years - assuming the system has not been rebooted in the interim) [[User:Sysin|Sysin]] ([[User talk:Sysin|talk]]) 11:28, 3 September 2016 (UTC)

I agree that the explanation is overly technical. A succinct explanation of the joke (the crux of which being that Cueball is actively trying to threaten a computer program) would be preferential to passing off a man page as an ExplainXKCD article. Although linking to a more detailed breakdown of how Cron functions isn't a bad idea at all. This is a pretty good one http://www.unixgeeks.org/security/newbie/unix/cron-1.html

1489: Fundamental Forces

2015-09-10T22:53:19Z

108.162.221.148: /* Explanation */

{{comic
| number = 1489
| date = February 20, 2015
| title = Fundamental Forces
| image = fundamental_forces.png
| titletext = "Of these four forces, there's one we don't really understand." "Is it the weak force or the strong--" "It's gravity."
}}

==Explanation==
[[Cueball]] is acting here as someone teaching physics at a basic level, perhaps a high school science teacher. He seems to understand the general idea of the {{w|Fundamental interaction#Overview of the fundamental interaction|four fundamental forces}}, but his understanding gets progressively more sketchy about the details. The off-panel audience, probably a student or class, is interested, but quickly begins to realize Cueball's lack of understanding. Instead of acknowledging the problem directly, Cueball simply blusters onwards.

The comic also outlines how progressively difficult it gets to describe the forces. {{w|Gravitation|Gravity}} was first mathematically characterized in 1686 as {{w|Newton's law of universal gravitation}}, which was considered an essentially complete account until the introduction of {{w|general relativity}} in 1915. The {{w|Electromagnetism|electromagnetic force}} does indeed give rise to {{w|Coulomb's law}} of {{w|electrostatics|electrostatic}} interaction (another {{w|inverse-square law}}, proposed in 1785), but a much more comprehensive description, covering full {{w|Classical electromagnetism|classical electrodynamics}}, was only given in {{w|Maxwell's equations}} around 1861. The {{w|strong interaction|strong}} and {{w|weak interaction|weak}} forces cannot easily be summarized as comparably simple mathematical equations. It's possible that Cueball does understand the strong and weak interactions, but is completely at a loss when he tries to describe them.

The strong force doesn't act directly between {{w|proton}}s and {{w|neutron}}s but between the {{w|quark}}s that form them. Unlike gravity and electromagnetism, the strong force {{w|Asymptotic freedom|gets stronger with increasing distance}}: It is ''loosely'' similar to the {{w|Hooke's law|restoring force of an extended spring}}. However, all stable heavy particles are neutral to the strong force, due to being made up of three "{{w|quantum chromodynamics|colors}}" (or a color and the appropriate "anticolor") of quarks. Between protons and neutrons there is a residual strong force, analogous in some ways to the {{w|van der Waals force}} between molecules. This residual strong force is carried by {{w|pion}}s and does decrease rapidly and exponentially with distance due to the pions having mass.

The weak force is much weaker than electromagnetism at typical distances within an atomic nucleus (but is still stronger than gravity), and has a short range, so has very little effect as a ''force'', but has the property of changing one particle into another. It can cause a down quark to become an up quark, and in the process release a high energy electron and electron anti-neutrino. This is known as {{w|beta decay}}, a form of radioactivity. Over even shorter distances, {{w|electroweak theory|and much higher temperatures}}, the weak interaction and electromagnetism are essentially the same.

The title text refers to the fact that it is gravity that appears to be the simplest and easiest to understand of the four forces, but turns out to be the {{w|Quantum_gravity|hardest to reconcile}} with a coherent (quantum) understanding of {{w|Theory of everything|all four forces together}}.

==Transcript==
:[Cueball is holding his hands up while giving a lecture to an off panel audience.]
:Cueball: There are four fundamental forces between particles:
::(1) '''''Gravity''''', which obeys the inverse square law:
::: Fgravity = G m1m2/d2

:Off panel audience: OK...

:[Cueball is still holding his hands up while continues the lecture to the off panel audience.]
:Cueball: (2) '''''Electromagnetism''''', which obeys ''this'' inverse-square law:
:::Fstatic = Ke q1q2/d2

::...and also Maxwell's equations
:Off panel audience: Also what?

:[Zoom in on Cueball as he continues the lecture to the off panel audience.]
:Cueball: (3) The '''''strong nuclear force''''', which obeys, uh ...
:::...well, umm...
::...it holds protons and neutrons together.
:Off panel audience: I see.
:Cueball: It's strong.

:[Cueball finishes the lecture to the off panel audience and spreads out his arm for the final remark.]
:Cueball: And (4) the '''''weak force'''''. It [mumble mumble] radioactive decay [mumble mumble]
:Off panel audience: That's not a sentence. You just said “Radio-
:Cueball: – '''''And those are the four fundamental forces!'''''

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Physics]]