Thickness of human hair, and unwarranted precision

[pne]

Out of random interest, I wondered how thick a human hair is.

(What brought it to mind was reading about people flossing their teeth with their own hair, and wondering how wide a hair is. Plus recently reading about how proud Google are about their natural language processing and trying to give you what you want rather than what you asked for.)

The first page I found was this one, which collected a few other sources.

One of those made me weep.[*]

http://www.av.qnet.com/~dennyr/ apparently (the URL is 404 now) said: "Diameter of a human hair: inches: 0.001; centimeters: 0.00254".

Really? 0.00254 cm?

That would imply 0.00100 inches, not just 0.001.

It's like saying "Oh, he lives at least twenty miles [32.187 km] away!". Or even, "Of the seven participants, two (28.57%) tested positive for the dreaded lurgy."

Unwarranted precision makes me cry. ([*] Well, figuratively, at least.)

(Oh, and the answer to my question? Is apparently "it depends". Though 10–100 µm is apparently the basic order of magnitude.)

---

Oh dear, I just looked at the second hit I had opened in a tab. It contains this gem:

"Most is around 0.004 inches.
This equates to 0.0003333333333333333333333333333333333333333333333 feet !!!!

Ow, it burns, it burns!

Comments

[joyitude.livejournal.com]

"(What brought it to mind was reading about people flossing their teeth with their own hair, and wondering how wide a hair is. Plus recently reading about how proud Google are about their natural language processing and trying to give you what you want rather than what you asked for.)"

I understand the first part of that and how it relates to what you said. The second part confuses me to no end.

[pne.livejournal.com]

Oh, sorry.

I was reading this article (http://googleblog.blogspot.com/2008/07/technologies-behind-google-ranking.html) specifically.

And how it relates is that I figured that if Google is so "smart", then a query such as "thickness of human hair" should get me what I want regardless of what the sites holding the answer call it specifically.

[pthalo]

oh, interesting.

One thing I've been particularly impressed with is with the searches I've made in Serbian. Google understands the case system and will find "slici" and "sliku" as well as "slika" (picture). Google understands gender and if i searched for gladan i'd probably get gladna and gladno as well. It's especially useful in languages like Hungarian, though I haven't fully tested the extent of it's ability to handle hungarian agglutination.

If i want to look for biographies, I want to type életrajz, not
életrajz OR életrajzok OR életrajzom OR életrajzod OR életrajza OR életrajzinkat OR életrajzhoz OR életrajzakat OR ....... ∞

[joyitude.livejournal.com]

Ahhhh. That makes sense.

[leora.livejournal.com]

I am against sig fig abuse. I even wrote one strip of my comic on this topic.

[pthalo]

I'm 24.05879 years old ;) (+6 minutes)

[pne.livejournal.com]

What'd you use to convert that? units(1)?

I'm 33.6732 years old :) (+1 minute)

[pthalo]

24 + (21/365) + (however many hours it was/(365*24)

[eva]

Oh, and the answer to my question? Is apparently "it depends

Definitely. For example, white hairs are, as far as I know, somewhat thicker than others. This leads to the annoying effect of single white hairs always sticking out in other directions than the rest, which makes sure that everybody notices I have them. (Yes, I started to get white hairs with 24. Sigh.)

[pne.livejournal.com]

Und ich dachte immer, graues Haar wäre erblich -- man bekomme es von seinen Kindern. Und die hast du ja noch gar nicht!

[eva]

Nee, das kam bei mir vom Studium. Kaum hatte ich den ersten Abschluß und dachte, ich könnte mich erholen, fing es an zu sprießen.

Vielleicht sind aber auch die Kinder in meinen Kinderchören schuld.

[fledchen.livejournal.com]

That kind of precision makes no sense given the degree of variability in hair thickness.

[pne.livejournal.com]

Good point.

[allegrox.livejournal.com]

The original numbers were apparently rounded, and whoever converted them doesn't know about significant digits.

[pne.livejournal.com]

whoever converted them doesn't know about significant digits.

Yep.

(Though I read that the figure of 98.6 °F for human body temperature is also such a victim -- that it was based on a study which came up with a temperature of 36.x °C [for some x >= 5], which was rounded to 37 °C [partly because of the natural variation in body temperature, I can imagine]. So it should be 98 °F (I think), since you're converting 37 °C, not 37.0 °C.)