Do a curly-haired person's curly hairs all have the same chirality?

June 5, 2008 6:32 AM

Do a curly-haired person's curly hairs all (or nearly all) have the same chirality (i.e., left-handed coils or right-handed coils)? Does it vary from person to person?
posted by Wolfdog to Science & Nature (10 answers total)

Mine do mostly, but not entirely.

Storytimefilter: in 1957, just after the discovery of parity nonconservation, Norman Ramsey and some other giant of physics happened to drive past a farm with a full pigpen. They exchanged a look and got out of the car. There were twenty pigs in the pen. They agreed that Ramsey would count all the pigs with left-handed tails, and the other all the pigs with right-handed tails. After a bit they compared notes: twelve left and nine right? Try again ... ten left and eleven right? They stopped and watched a single pig's tail, which curled left. After a bit the tail straightened out and curled to the right.
posted by fantabulous timewaster at 6:57 AM on June 5, 2008 [19 favorites]

I don't think so, at least not for me. If my hair is wet I can wind a curl to go in either direction, and it will stay that way when dry. Also, different sections of my hair have different degrees of curl.
posted by cabingirl at 7:20 AM on June 5, 2008

Mine tend to coil toward my face, which means they're curling different directions depending on which side of my head they're on, and they just kind of meet in a tangly mish-mash in the back.
posted by amyms at 7:21 AM on June 5, 2008

Mine tend to curl toward my face as well.
posted by k8t at 7:27 AM on June 5, 2008

The direction of the curl isn't really endemic to the hair; it wants to curl, but it doesn't care which way, like a coiled phone cord. Individual hairs can have their coils reversed with a twist. Clumps of curls are harder to reverse, especially if they're always styled the same way, but the direction of the curl is not immutable.

How can I speak so authoritatively on the subject? Because I am ulotrichous.
posted by ulotrichous at 8:00 AM on June 5, 2008 [2 favorites]

Mine tend to coil toward my face, which means they're curling different directions depending on which side of my head they're on, and they just kind of meet in a tangly mish-mash in the back.

Not necessarily, because the skin on your face points in a different direction on each side.

I wrote a long post on this but it was a little confusing. Let me try to write this more concisely.

Okay, so imagine the tangent of your hair as it comes out of your head (that is the direction it's pointing before it starts curving). Then imagine a plane that contains that vector and is perpendicular to your skin. Lets say that the normal of that plane is the dot product of the first vector and the line of intersection between that plane your skin in the 'small angle'.

Okay. In that case, in that plane, I think my hairs always curl in the counterclockwise direction, and also I think thats the case for more people.

The other thing to look at is how the hairs 'wind' if they get long enough to do so. That is, the direction that the hairs wind as they move away from your skin. But I actually think that's just determined by gravity or other factors, not by the hair itself.

I spent way too much time thinking about this :P
posted by delmoi at 8:04 AM on June 5, 2008

delmoi, I think you have the geometry wrong. The relevant directions are the direction the hair grows ("normal to the skin" or so) and the direction of the twist, which most people relate using the "right-hand rule." If the hair from both temples curls towards the face, the hair coming from the right temple is left-handed and the hair coming from the left temple is right-handed. You can see this if you put your fists on your ears so your thumbs stick out: the fingers on your right- and left-handed hands both point to the back of your head. ulotrichous has it.

You think you devote too much thought to this? back to thesis
posted by fantabulous timewaster at 8:41 AM on June 5, 2008

My hair also curls toward my face, and therefore curls in different directions. If you were to look at the back of my head, you would see 2 locks of hair right next to each other. One lock would be curling to the left, and one to the right.
posted by bluefly at 11:30 AM on June 5, 2008

My hair curls in different directions on the same hair. While some of my curls are one long spiral, some of them spiral, then have a section where the curl sort of 'opens' (like what a phone cord does when you begin to uncurl it) and then starts to curl the other way.
posted by Kololo at 12:26 PM on June 5, 2008

I have some that do what Kololo is describing. But I can recurl them into whichever direction and they generally stay. I think both sides curl the same way, so one towards and one away from my face, whereas the back doesn't really curl properly at all.

All of which reminds me I really need a haircut.
posted by shelleycat at 11:02 PM on June 5, 2008