0849: "Complex Conjugate"

This forum is for the individual discussion thread that goes with each new comic.

Moderators: Moderators General, Prelates, Magistrates

soren121
Posts: 53
Joined: Thu Jun 19, 2008 7:25 pm UTC

0849: "Complex Conjugate"

Alt-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.

No idea what a complex conjugate is, but I'm assuming it's something dreaded.

EDIT: Oh, I get it now: the teacher dropped the imaginary part. Thanks to Randall for making me research my most hated subject at midnight.
Last edited by soren121 on Wed Jan 19, 2011 5:08 am UTC, edited 2 times in total.
PHP/XHTML/CSS Programmer
http://www.sorenstudios.com/
Fueled by all of this and V8

meat.paste
Posts: 404
Joined: Fri Apr 25, 2008 3:08 pm UTC

Re: 0849: "Complex Conjugate"

I thought, "that's cute." Then I read the title text and did a simultaneous facepalm and LOL. Very nice.
Huh? What?

ST47
Posts: 125
Joined: Tue Oct 16, 2007 6:42 pm UTC

Re: 0849: "Complex Conjugate"

Alternately, if you have a complex number a+bi, the complex conjugate is a-bi. So, multiplying these together gives (a^2+abi-abi-b^2*i*2)=(a^2+b^2). Which, as you'll note, happens to be real.
Therefore, shit just got real.

j16sdiz
Posts: 2
Joined: Fri Sep 24, 2010 4:30 am UTC

Re: 0849: "Complex Conjugate"

soren121 wrote:No idea what a complex conjugate is, but I'm assuming it's something dreaded.

EDIT: I'm assuming in this problem that multiplying the waveform by its complex conjugate would yield a real number. Thanks to Randall for making me research my most hated subject at midnight.

No, complex conjugate make YOU become real.

shashwat986
Posts: 60
Joined: Wed Mar 24, 2010 10:15 am UTC

Re: 0849: "Complex Conjugate"

AWESOME!!!

A complex number is of the form a + ib where a and b are real number, and i=sqrt(-1)
It's conjugate will be a - ib. If we multiply them together, we get: (a + ib)(a - ib) = a^2 + b^2 which is always real.

Just thought I'd clear the air a bit.

EDIT: Whoops... Seems I'm the second guy to explain that
Apparently, 1 in 5 people in the world are Chinese. And there are 5 people in my family, so it must be one of them. It's either my mum or my dad. Or my older brother Colin. Or my younger brother Ho-Chan-Chu. But I think it's Colin -- Tim Vine

Belteshazzar
Posts: 4
Joined: Fri Dec 31, 2010 3:59 pm UTC

Re: 0849: "Complex Conjugate"

I have a math professor who is in the habit of saying things like "... defines a real Banach space. (pause) A real Banach space, Daddy? Yes, son, a real Banach space."

Mazuku
Posts: 133
Joined: Tue Aug 10, 2010 4:48 am UTC
Location: South Australia

Re: 0849: "Complex Conjugate"

The maths involved here is way beyond me abd if the strip is anything to go by, is way beyond even many maths geeks, am I right?
Allmächtige Exzentrikerin3

...................................

Retsam
Posts: 57
Joined: Tue Aug 18, 2009 5:29 am UTC

Re: 0849: "Complex Conjugate"

It's actually really not that high level of math; just moderately obscure. They're one of the most basic principles of imaginary numbers, so I think we talked about them in High School Algebra when we briefly discussed imaginary numbers.

Steve the Pocket
Posts: 707
Joined: Mon Apr 23, 2007 4:02 am UTC
Location: Going downtuuu in a Luleelurah!

Re: 0849: "Complex Conjugate"

I'd never heard the phrase "complex conjugate" before (it sounds like a grammar term), and I only knew the term "wavefunction" from descriptions of the Schrodinger's cat thing (still don't know what it means... something to do with quantum mechanics I suppose), but I was still able to figure out that the punchline had to do with imaginary numbers.

And now that I know that quantum physics involves imaginary numbers, it makes a little more sense why people tend to find it so alien. Literally, if you happen to work for Valve.
cephalopod9 wrote:Only on Xkcd can you start a topic involving Hitler and people spend the better part of half a dozen pages arguing about the quality of Operating Systems.

Baige.

Snkz
Posts: 3
Joined: Wed Jan 19, 2011 5:17 am UTC

Re: 0849: "Complex Conjugate"

I'm sure many of you have seen a conjugate before. It does not have to involve complex numbers at all. Many times with fractions, multiplying the numerator and denominator by the denominators conjugate allows for some simplification tricks. Its done a lot with trig fractions.

Draco18s
Posts: 89
Joined: Fri Oct 03, 2008 7:50 am UTC

Re: 0849: "Complex Conjugate"

Reminds me of a friend of mine who had 3 cans of Nos (energy drink) and walked into calculus and played a drinking game.

Every time the professor said, "z" he would take a shot of Nos. It was not a good day to pick "z," as every function that day was a z= function.

Hour later he was 9 shots behind and the professor had slowed down to let him catch up.

Three hours later I saw him and he was speaking so fast I couldn't understand him.

s0merand0mdude
Posts: 37
Joined: Fri Dec 04, 2009 6:35 am UTC

Re: 0849: "Complex Conjugate"

A math/science joke I actually get! I just learned this stuff last week! Whoo for the education system!!
unus vox wrote:Then again, you're looking for characterization, compelling dialogue, and cohesion in a 3-panel web comic with stick figures.

Tyrannosaur
Posts: 107
Joined: Thu Sep 02, 2010 5:39 am UTC

Re: 0849: "Complex Conjugate"

j16sdiz wrote:No, complex conjugate make YOU become real.

Only in soviet russia.
Last edited by Tyrannosaur on Wed Jan 19, 2011 6:29 am UTC, edited 1 time in total.
djessop wrote:The t-shirt should read "There are 11 types of people in the world, those who understand binary, those who don't and those who insist the number above is pronounced as eleven no matter what base you're in".

Andromeda321
Posts: 123
Joined: Fri Sep 18, 2009 11:31 pm UTC

Re: 0849: "Complex Conjugate"

I'm trying to figure out how sad it is that I had a friend in undergrad physics who would say this during our homework sessions for quantum. Or awesome, depending who you ask.

Mike_Bson
Posts: 252
Joined: Mon Jul 12, 2010 12:00 pm UTC

Re: 0849: "Complex Conjugate"

Since I love complex analysis, this is my new favorite comic.

torontoraptor
Posts: 442
Joined: Sun Apr 12, 2009 11:58 pm UTC

Re: 0849: "Complex Conjugate"

I just giggled for 30 seconds straight. This right here, this is why the world is awesome.*

*well this along with a myriad of other things that it would be exhaustive and rather pointless to write out
Promicin wrote:Now if I can just grab on with my tongue-like foot... wait. I am not a mussel.

pseudoidiot wrote:
You, sir, name? wrote:fucking owls is enjoyable.
Someone should sig this

sedoris
Posts: 2
Joined: Wed Jan 19, 2011 5:47 am UTC

Re: 0849: "Complex Conjugate"

Lol, I'm in quantum chemistry right now and we're just starting to talk about wavefunctions now. I lol'd. Thanks randall

sugarhyped
Posts: 548
Joined: Wed Feb 27, 2008 5:16 am UTC
Location: california

Re: 0849: "Complex Conjugate"

I read the comic and the alt text a couple times. Then I re-read the punch line and literally lol'ed. I surprised my self because usually im just or
I wanted a signature. I don't know what to put here yet.

dysprog
Posts: 22
Joined: Tue Aug 24, 2010 5:45 am UTC

Re: 0849: "Complex Conjugate"

Ok, the cheese is well toasted, but I did not get the alt-text. Was there another joke that that I was supposed to see?

wisnij
Posts: 427
Joined: Mon Jun 26, 2006 5:03 pm UTC
Location: a planet called Erp
Contact:

Re: 0849: "Complex Conjugate"

Pose as a team, because... wait, wrong webcomic.
I burn the cheese. It does not burn me.

black_hat_guy
Posts: 111
Joined: Tue Jul 20, 2010 8:34 pm UTC

Re: 0849: "Complex Conjugate"

This comic would be almost as funny if real numbers were not called real. The alt-text implies that Randall has done this before to a professor, and the whole thing is kind of absurd if you think about it.
Billy was a chemist.
He isn't any more.
What he thought was H2O
was H2SO4.

Eternal Density
Posts: 5589
Joined: Thu Oct 02, 2008 12:37 am UTC
Contact:

Re: 0849: "Complex Conjugate"

Yes, multiplying something by its complex conjugate results in a real number. In this comic, Randall turns this into a terrible pun and then points out that repeating such a terrible pun will annoy people to the point that they ditch you. Thanks, Einstein.
Play the game of Time! castle.chirpingmustard.com Hotdog Vending Supplier But what is this?
In the Marvel vs. DC film-making war, we're all winners.

cyanyoshi
Posts: 418
Joined: Thu Sep 23, 2010 3:30 am UTC

Re: 0849: "Complex Conjugate"

Eternal Density wrote:Yes, multiplying something by its complex conjugate results in a real number. In this comic, Randall turns this into a terrible pun and then points out that repeating such a terrible pun will annoy people to the point that they ditch you. Thanks, Einstein.

Almost makes me want to not let Randall get away with putting such bad puns on his webcomic...

Almost.

pyroman
Posts: 346
Joined: Sun Feb 10, 2008 5:35 am UTC
Location: University at Buffalo
Contact:

Re: 0849: "Complex Conjugate"

This one had me laughing for a good 30 sec. I got to take plenty of signals classes so I was doing this all the time much to the displeasure of everyone around me... oh who the hell am I kidding? My friends are all just as nerdy as I am. They found it hilarious as well (well at least the first few times... )
They who can give up essential liberty to obtain a little temporary safety, deserve neither liberty nor safety. - Benjamin Franklin

Byerley
Posts: 1
Joined: Wed Jan 19, 2011 6:30 am UTC

Re: 0849: "Complex Conjugate"

It may be moderately obscure math, but it's really common in physics. In electronics and quantum especially, probably other branches too that aren't coming to mind, it's much easier to work with the functions in imaginary space, but you need to take the projection onto real space at some point to get an observable value out of it. I do it all the time, but it still took ~30s of blank staring to finally get the pun . Maybe I'm just bad at puns.

tntc
Posts: 1
Joined: Wed Jan 19, 2011 7:04 am UTC

Re: 0849: "Complex Conjugate"

I have to confess, sometimes I laugh at XKCD despite having no idea what anything in the first three panels meant. That's right, shit just got fake.

fenrir_darkwolf
Posts: 104
Joined: Thu Mar 27, 2008 10:21 pm UTC

Re: 0849: "Complex Conjugate"

soren121 wrote:Thanks to Randall for making me research my most hated subject at midnight.

What's your most hated subject? Quantum mechanics? Have you taken a quantum course? It's quite nice once you get over how much maths formalism there is (not that there is anything wrong with maths formalism )
"You're gonna have to learn everything anyway, so which is first is not essential."
-Richard Feynman

fenrir_darkwolf
Posts: 104
Joined: Thu Mar 27, 2008 10:21 pm UTC

Re: 0849: "Complex Conjugate"

Mike_Bson wrote:Since I love complex analysis, this is my new favorite comic.

Nice avatar btw . Guess we both got action this comic.
"You're gonna have to learn everything anyway, so which is first is not essential."
-Richard Feynman

Max2009
Posts: 160
Joined: Mon Mar 09, 2009 2:20 pm UTC
Location: Where?
Contact:

Re: 0849: "Complex Conjugate"

I hate complex numbers. I mean, calculus was hard enough to begin with, why the hell did they have to go and invent imaginary numbers? Were they deprived of imaginary friends as children and now want to get back at the rest of the world?

On topic, that was one of the worst math puns I've ever heard. Well done Randall.

dysprog wrote:Ok, the cheese is well toasted, but I did not get the alt-text. Was there another joke that that I was supposed to see?

No, it's not a joke. It's true.
Try it.
Cogito ergo surf - I think therefore I network

Registered Linux user #481826 Get Counted! http://counter.li.org

Tetrinity
Posts: 3
Joined: Wed Jan 19, 2011 7:42 am UTC

Re: 0849: "Complex Conjugate"

I actually have an Algebra exam in about an hour and a quarter, and really wasn't looking forward to it. This comic made me burst out laughing, and I must say I'm feeling quite a bit better about it. Now I just need to make sure I don't laugh everytime I use the complex conjugate of a number in the exam...

"(4-3i)/(2+i), eh? Okay, no problem, let's just multiply top and bottom by the complex conjuga- BWHAHAHAHAHAAAAAAA"

Mike_Bson
Posts: 252
Joined: Mon Jul 12, 2010 12:00 pm UTC

Re: 0849: "Complex Conjugate"

Max2009 wrote:I hate complex numbers. I mean, calculus was hard enough to begin with, why the hell did they have to go and invent imaginary numbers? Were they deprived of imaginary friends as children and now want to get back at the rest of the world?

Moments like this make me feel like the only person in the world who likes complex numbers as much as I do.

KShrike
Posts: 129
Joined: Wed Dec 15, 2010 5:47 am UTC

Re: 0849: "Complex Conjugate"

Nice! I would love to be back in High School right now. Not so I can say it, but so I can hear someone else say it. Unfortunately, people won't be saying that statement where I am going.
On 10/10/10, My Little Pony started to appeal to adult males. Ya rly!
Forget the /b/ memes, and go watch the show and see what I mean. After all, the /b/ memes exist because the show itself is so cleverly written. Check it out!

Mapar
Posts: 129
Joined: Wed Jun 16, 2010 11:26 am UTC

Re: 0849: "Complex Conjugate"

This comic had me laughing out loud, genuinely. I liked it.
Hi.

Lucia
Posts: 95
Joined: Sun May 09, 2010 1:35 am UTC

Re: 0849: "Complex Conjugate"

Once I got that the guy wasn't the professor, I chuckled.
Wildhound wrote:Nobody ever sigs me. I think it's because I never say anything clever.

NotAllThere
Posts: 146
Joined: Fri Aug 06, 2010 12:54 pm UTC

Re: 0849: "Complex Conjugate"

Complex numbers are very cool and interesting objects. Some infinite series don't really make sense if you only consider the field or reals. Euler's identity makes sense when it's considered as a rotation in the complex plane. They're absolutely essential to much physics and engineering and very helpful for solving certain polynomials.

Complex conjugates are used in complex division, converting it to multiplication. w/z = w/z times z'/z' = (w.z') / (z.z') = (w.z')/x Where w and z are complex numbers, z' is the complex conjugate of z, and x is a real number.
yangosplat wrote:So many amazing quotes, so little room in 300 characters!

ramparts
Posts: 22
Joined: Mon Oct 01, 2007 8:33 pm UTC

Re: 0849: "Complex Conjugate"

Wow, props to Randall for three physics/astro based comics in a row (and all pretty funny ones, too). I approve!

Mazuku wrote:The maths involved here is way beyond me abd if the strip is anything to go by, is way beyond even many maths geeks, am I right?

Absolutely not - a maths geek who's graduated high school should get this.

Belteshazzar wrote:I have a math professor who is in the habit of saying things like "... defines a real Banach space. (pause) A real Banach space, Daddy? Yes, son, a real Banach space."

EDIT: And apparently after 4 months of studying in England, I've taken to alternating between "math" and "maths." :facepalm:
Last edited by ramparts on Wed Jan 19, 2011 10:26 am UTC, edited 1 time in total.

Ronfar
Posts: 132
Joined: Mon Dec 04, 2006 6:04 am UTC

Re: 0849: "Complex Conjugate"

Max2009 wrote:I hate complex numbers. I mean, calculus was hard enough to begin with, why the hell did they have to go and invent imaginary numbers? Were they deprived of imaginary friends as children and now want to get back at the rest of the world?

Amazingly enough, calculus actually gets easier when you introduce complex numbers. Trying to do calculus on functions of two or more real variables quickly becomes a real pain in the neck, but if you can use a complex function instead, things become much simpler. You don't have to worry about such things as curl, divergence, the del operator, or any of that other stuff - if the function has "is analytic" and has a derivative at all, you can find it the same way you find derivatives of real functions. And analytic functions have all sorts of other properties that make them easier to work with, too.

Also, to answer your other question, imaginary numbers were invented in order to solve cubic equations - when you plug numbers into the cubic formula, you sometimes end up having to deal with imaginary terms in the process of getting your answer, even if all three roots are real.
- Doug

Nyerguds
Posts: 62
Joined: Mon Aug 27, 2007 7:43 am UTC

Re: 0849: "Complex Conjugate"

soren121 wrote:Alt-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.

IT'S TITLE-TEXT DAMMIT!

(...this board needs a RAAAAGE smiley -_-)

I got it from the moment I read the title text. Never done this in physics, and complex-number math has been a while ago for me.

Auliya
Posts: 8
Joined: Sun Feb 01, 2009 11:40 pm UTC

Re: 0849: "Complex Conjugate"

"Get out of my head, Randall!"

I'm studying Optoelectronics right now, and although the complex domain is nothing new for me, theese days even a simple complex conjugate can put me in a state of stupor, where I stare at the page for two minutes without actually seeing the formulae in front of me.

EDIT: @fenrir_darkwolf: I wish I hadn't noticed your avatar... there's no escape!

Monika
Welcoming Aarvark
Posts: 3673
Joined: Mon Aug 18, 2008 8:03 am UTC
Location: Germany, near Heidelberg
Contact:

Re: 0849: "Complex Conjugate"

Meh. Old joke. Really old. Stale. There are already T-shirts with it.

But I LOL'd at the alt text .
#xkcd-q on irc.foonetic.net - the LGBTIQQA support channel
Please donate to help these people