849: Complex Conjugate

Explain xkcd: It's 'cause you're dumb.
Revision as of 05:25, 21 July 2013 by Markhurd (Talk | contribs)

Jump to: navigation, search
Complex Conjugate
Fun fact: if you say this every time a professor does something to a complex-number equation that drops the imaginary part, they'll eventually move the class to another room and tell everyone else except you.
Title text: Fun fact: if you say this every time a professor does something to a complex-number equation that drops the imaginary part, they'll eventually move the class to another room and tell everyone else except you.

Explanation

This comic is a joke on the common phrase "Shit just got real", meaning that something has suddenly increased in difficulty so it is now a real challenge. Cueball is standing in front of a board delivering a lesson, and is about to multiply a wavefunction by its complex conjugate. In mathematics, a complex number has a real part (a) and an imaginary part (b*the imaginary unit). The number can be written as a+bi. The complex conjugate of a number (a+bi) is a-bi. When one multiplies a complex number and its conjugate, the result is (a+bi)(a-bi), which is a^2+b^2. This process yields a number that does not have the imaginary part, making it real, which is a play on the aforementioned phrase. Accordingly, Cueball dictates that the people who are not skilled enough should leave.

The title text states that if you joke about this every time it's applicable, that will be annoying enough that the class will ditch you and attempt to take place in another room.

Transcript

[Cueball is standing at a whiteboard covered in equations, one of which is the time dependent Schrodinger equation.]
Cueball: Okay, anyone who's feeling like they can't handle the physics here should probably just leave now.
Cueball: Because I'm multiplying the wavefunction by its complex conjugate.
Cueball: That's right.
[Dramatic zoom. It appears Cueball is writing on the side of the panel.]
Cueball: Shit just got real.
comment.png add a comment! ⋅ Icons-mini-action refresh blue.gif refresh comments!

Discussion

Actually multiplying complex number (x + iy) by its complex conjugate (x - iy) does not "remove" imaginary part, but calculate square of absolute value of complex number, (x^2 + y^2). BTW. in quantum physics the wavefunction is complex valued, and its absolute value is probability density (a real valued function). --JakubNarebski (talk) 00:57, 18 December 2012 (UTC)

I got hit in the face with my complex conjugate and lost an eye. 108.162.238.114 (talk) (please sign your comments with ~~~~)

I procreated with my complex conjugate and lost myself. 108.162.216.114 19:44, 12 August 2014 (UTC)
Personal tools
Namespaces

Variants
Actions
Navigation
Tools

It seems you are using noscript, which is stopping our project wonderful ads from working. Explain xkcd uses ads to pay for bandwidth, and we manually approve all our advertisers, and our ads are restricted to unobtrusive images and slow animated GIFs. If you found this site helpful, please consider whitelisting us.

Want to advertise with us, or donate to us with Paypal or Bitcoin?