228: Resonance

Explain xkcd: It's 'cause you're dumb.
Jump to: navigation, search
It's really hard to control the frequency, actually.
Title text: It's really hard to control the frequency, actually.


Resonance is the tendency for an object to oscillate when energy is transferred to it at a specific set of frequencies known as harmonics of the natural frequency of the object. A simple example of this is pushing a child on a swing: by pushing the child at the right moment, more and more energy is transferred to the system and the amplitude of the oscillation grows, making the child swing higher.

In this comic, the friend is jiggling his leg up and down at a harmonic of the natural frequency of Cueball's desk. This causes Cueball's desk to vibrate more and more until objects on it start to bounce around. Rather than have the friend stop, Cueball wants him to slightly increase the frequency of the jiggling in order to spill the drink on Steve's desk (not pictured). In xkcd, no one (except Adam) likes Steve, as demonstrated in comics 1532: New Horizons and 1672: Women on 20s as well as this one. However, it is hard to have a person control a subconscious movement exactly, let alone increase or decrease by exact figures.

In the title text, his friend confesses the obvious fact that he couldn't control the frequency very well. (Alternatively, Randall may have made this observation himself through experimentation.)


[Cueball is sitting at a desk, which is vibrating.]
clatter clatter
[He leans back and turns to face someone sitting at another desk behind him.]
Cueball: Excuse me--you're jiggling your leg up and down. It's traveling through the floor and making my desk resonate.
Friend: Oh, I didn't even realize! I'll stop.
[Cueball passes a sheet of paper to the friend.]
Cueball: Actually, can you just shift the frequency up by 15%? I think you can get resonance with Steve's desk instead.
Friend: Uh huh...
Cueball: Here are the calculations. Let's coordinate and try to spill his drink.

comment.png add a comment! ⋅ comment.png add a topic (use sparingly)! ⋅ Icons-mini-action refresh blue.gif refresh comments!


How do you guys know which one is Cueball? 19:52, 10 October 2014 (UTC)

In general, the first one to talk is referred to as Cueball. 21:13, 23 March 2015 (UTC)

So, was it because his drink got spilled that Steve screwed up the calculations for the Jupiter slingshot, causing New Horizons to return to Earth (and his eventual demise under a pile of burning spacecraft wreckage)? Does this make Cueball a murderer? 11:41, 5 June 2015 (UTC)

What If? and Xkcd mention Steve and New Horizons. 22:47, 15 November 2015 (UTC)

Is there an explanation of why people's legs tend to want to jiggle like that? I get that and can never explain why. 00:56, 2 March 2017 (UTC)

This is called Restless Leg Syndrome. (talk) (please sign your comments with ~~~~)
No it isn't, that's a compulsive urge to move your legs. The leg bounce in the comic is a nerve reflex movement caused by the exact angle the joints in your leg make. If you move your foot slightly you can't produce the same rhythmic motion. It is not even a "subconcious" movement, because it is controlled entirely outside of your brain - it is the same mechanism that causes your leg to kick when the doctor hits it with a hammer - only this forms a cycle where the leg drops, stretching the tendon, which causes the reflex, which straightens your foot, lifting your leg, relaxing the tendon, only for your leg to drop again and so on.

Anybody else think that the earthquake comic in [1] could be referencing this comic? Or does everybody consider that opinion to be stupid?-- 16:00, 25 November 2019 (UTC)

The statement "In xkcd, no one likes Steve" is factually incorrect. Adam likes Steve (see the title text on 1003:_Adam_and_Eve). Could someone correct that? 14:24, 5 June 2023 (UTC)

There you go! -- 08:11, 23 January 2024 (UTC)