2316: Hair Growth Rate

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Hair Growth Rate
Hourly haircuts would be annoying, but they'd be easier to do yourself, since you'd have adjacent hairs as a guide. Growing it out would be a huge pain, though.
Title text: Hourly haircuts would be annoying, but they'd be easier to do yourself, since you'd have adjacent hairs as a guide. Growing it out would be a huge pain, though.


This strip is one of the simpler jokes that xkcd has done, being an observation on mathematics, biology, and human expectation. White Hat starts by sharing various facts about hair with Ponytail; hair count, individual hair growth rate, and finally total hair growth rate. Ponytail proceeds to snark about how unpleasant it would be if, rather than 100,000 hairs growing at a gross total of five feet (1.524m) per hour, humans grew a single new five-foot-long hair once per hour. The comic then delves into the absurdity of gradual versus spontaneous growth, and then the sound effects involved therein.

The comic touches on what information can be obscured by just looking at aggregate values. A person whose 100,000 hairs grow a half-inch (1.27cm) per month experiences the same total new hair growth as a person with one hair growing five feet in an hour, but their grooming experiences would be very different. Likewise, a person with one hair growing steadily for an hour has the same average rate of hair growth as a person experiencing sudden hair growth on the hour, but the profile of instantaneous energy conversion and protein production would be very different. One of Ponytail's suggestions for what five feet of instantaneous hair growth might sound like is a sound effect generally used for directed-energy weapons (Pew!).

We never see what sort of hairstyle White Hat has under his hat, but Ponytail's hair is fairly long. If she had to grow it out by one hair per hour, as in the title text, then it would take over eleven years before all 100,000 hairs had grown out.


[White Hat and Ponytail are walking to the right.]
White Hat: The average head has about 100,000 hairs.
White Hat: And hair grows at about ½" per month.
White Hat: Plus or minus.
Ponytail: Okay...
[They continue to walk while White Hat lift a hand up palm up.]
White Hat: So our heads are producing an inch of hair every minute.
Ponytail: I see.
[They continue to walk.]
Ponytail: I'm just glad it's evenly distributed. It would suck if we grew a single new five-foot-long hair every hour.
[White Hat and Ponytail are seen in silhouette from a distance. White Hat has lifted a finger up and while Ponytail has thrown both her arms out to the sides.]
White Hat: Hmm, would the hair grow steadily, or would it suddenly shoot out 5 feet on the hour?
Ponytail: If the latter, what noise would it make?
Ponytail: Ziiip? Pwiff?
White Hat: Fwip?
Ponytail: Blip.
White Hat: Zhooop.
Ponytail: Pew!

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Based on the rate at which I shed hair, mine must be growing at an above average rate or I'd be completely bald by now. ProphetZarquon (talk) 19:23, 5 June 2020 (UTC)

Is this a Dr. Seuss reference? The Zed "all have one strand of hair up on each of their heads, their hair grows very fast, so fast, people say that they need a haircut everyday" Usernaminator (talk) 21:18, 5 June 2020 (UTC)

So, anybody have some idea how is this related to covid? :-) -- Hkmaly (talk) 22:30, 5 June 2020 (UTC)

The link is clearly that there are no open barbers now! (THIS IS A JOKE) 22:54, 5 June 2020 (UTC)
i was like omigod a normal xkcd they freed randall celebrate celebrate!!!! 22:38, 5 June 2020 (UTC)

Unrelated to the comic, but I just want to point out that (at least on my monitor), the kerning for "LIVES" in the new header is less than ideal. The "I" and the "V" blend together, looking like an "N" -- at least at the resolution displayed and the distance I view from -- so my mind reads "LNES" and fills in the missing "I" as "black lines matter." Which, for stick figures generally drawn in black on a white background is true, but.... 23:01, 5 June 2020 (UTC)

We all noticed... Cosmogoblin (talk) 20:04, 7 June 2020 (UTC)

First time I post here, I hope I do it right. You say "we never see what sort of hairstyle White Hat has under his hat", but we actually do: [1] 22:25, 9 June 2020 (UTC)

Should we add a long to the What if page where he mentions 1 massive hair? I think it had something to do with whales hiding down planes.

Sound Effect Words[edit]

--JohnB (talk) 08:58, 6 June 2020 (UTC)

...while PewPewPewPewPew is the sound of a clerical error, when you have far too much seating to comfortably fit inside the church and end up with zero leg-room. 11:57, 6 June 2020 (UTC)

don't we see his hair in that one new year's comic -- 08:18, 20 February 2024 (UTC)