Urgent Mission
Urgent Mission
[Cueball is coming out of star shaped hole, the hole has black stripes in it. Cueball has one leg inside but the rest of his body outside the hole. He points one arm at Benjamin Franklin. Franklin is sitting in a chair at his desk writing with a quill on a piece of paper. He is drawn with square glasses and long hair, but only at the back of his head, leaving  most of his head bald.] Cueball: Benjamin Franklin? Franklin: Yes? Cueball: I bring a message from the future! I don't have much time. Franklin: What is it? Cueball: The convention you're setting for electric charge is backward. The one left on glass by silk should be the negative charge.
[Caption below the panel:] We were going to use the time machine to prevent the robot apocalypse, but the guy who built it was an electrical engineer.

Benjamin Franklin was one of the Founding Fathers of the United States . Aside from uniting most of his country against Great Britain 's rule, he was also a model of a renaissance man : an author, painter, musician, politician, postmaster, inventor, scientist, and diplomat. Some of his legacies include bifocals, the Franklin stove, an odometer for a horse-drawn carriage, the almanac, and abolitionist ideals. He has since been honored with the use of his image on the $100 bill.
Franklin also did several experiments regarding electricity , and invented the lightning rod . He discovered the fundamentals of electricity, including positive and negative charges, as well as the principle of conservation of charge. When Franklin first wrote down his notes for electricity, he defined a positive charge as one left on a glass rod by rubbing it with silk, and a negative charge as one left on rubber by rubbing it with fur. Without realizing it, this meant that he had assigned a negative value to the charge on the electron, later identified as the fundamental carrier of electrical charge.
In an electrical circuit, we envisage the charge to be flowing from positive to negative. This is analogous to energy flowing from a region of high temperature to one of low temperature, or a fluid moving from an area of high pressure to one of low pressure.  However, because an electron is negatively charged, the actual flow of electrons is in the opposite direction, from negative to positive. This reversal of the natural expectation has caused unnecessary confusion to many fledgling engineers.
In the comic, the invention of a time machine was commissioned with the intent of preventing a robot apocalypse like in Terminator movies, a recurring theme on xkcd. However, the Cueball that built and used the machine is an electrical engineer with misplaced priorities, believing that reversing Franklin's "mistake" takes precedence over eliminating a more immediate threat to the human race.
Cueball tells Franklin that the charge left on a glass rod by rubbing it with silk should be the negative charge, not the positive charge, because the friction removes electrons from the rod. This would not have been intuitive to Franklin, because the electron had not as of yet been discovered. Yet by telling Franklin to reverse the positive and negative conventions, this would ultimately result in an alternate universe where electrons are assigned a positive charge. One can only speculate what other changes this reversal of convention would lead to, as small changes tend to cascade into huge ones . Would the positron have been instead named the negatron? And would this affect the success of the Transformers franchise?
In the title text, Cueball defends his actions, stating that preventing the rise of dictators or pandemics is a fine idea, but here they have a chance of making the signs on "every damn diagram" make sense, which to him seems so much more important. Cueball is likely voicing Randall 's frustration with this breach of logic, albeit exaggerated to comedic levels.
[Cueball is coming out of star shaped hole, the hole has black stripes in it. Cueball has one leg inside but the rest of his body outside the hole. He points one arm at Benjamin Franklin. Franklin is sitting in a chair at his desk writing with a quill on a piece of paper. He is drawn with square glasses and long hair, but only at the back of his head, leaving  most of his head bald.] Cueball: Benjamin Franklin? Franklin: Yes? Cueball: I bring a message from the future! I don't have much time. Franklin: What is it? Cueball: The convention you're setting for electric charge is backward. The one left on glass by silk should be the negative charge.
[Caption below the panel:] We were going to use the time machine to prevent the robot apocalypse, but the guy who built it was an electrical engineer.
