Pictures are helpful for this sort of discussion, thanks. I see there’s more going on than I initially thought.
If I saw spirals in that picture without any reference, I’d call the top left one a “right-handed, counter-clockwise spiral” because it matches my right hand with the thumb up and fingers pointing in the direction of the curl.
But that’s not how it’s labeled, but the complete opposite. It looks like the labeler wants to follow the spiral from the outside to the center. Given that assumption, their labeling is consistent.
It’s a matter of convention. I visualize spirals from the center going out (matching how I draw one or define the curve r = a x theta) and that controls my perception. Apparently biologists visualize the spiral from the outside going in. Maybe because of how they probe the shells? Or, alternatively, their thumbs point down. Anyway, I’ll have to remember they do it backwards.
A spiral does not have a definite handedness, because you can view it from either side. A helix, however, does have a definite handedness. The convention I’ve usually seen is that a common “righty-tighty” screw is a right-handed helix. Most mollusc shells are a combination of a spiral and a helix, with the helical component giving them their handedness.
We certainly could. It’s a durn shame the mathematicians standardized the other way from how everybody else does it though.
There’s room in the world for more than one standard. But it’s real rare for one to be replaced by it’s polar (:)) opposite. Evolution, whether of critters or memes or standards, hates abrupt 180s.
That’s how twisted ropes are named, and they are helix shaped. We say the rope has a right twist (clockwise) or left twist. What’s more, a right twisted rope has to be coiled clockwise for storage or else it will kink up, a left twist counterclockwise. Coiling is just a spiral and is not helical, but anyone who made or worked with ropes for a living would soon realize that the way it was twisted during construction and the way it was coiled were really the same thing, and would have come up with a word for it.
There is supposedly evidence of twisted ropes from 17000 BC, but we know for sure ancient Egyptians made them because they left very detailed hieroglyphs showing advanced rope-making techniques. I would bet anything they knew clockwise twist and coil from a counter-clockwise twist and coil and had a name for both. Assuming such words existed, I suspect they were more likely to have gotten them from everyday rope making rather than describing molluscs.
So, suppose you have two workers standing on either side of a spool, and they’re coiling a right-twisted rope onto it. Which worker gets to say which way to coil it?
You have to follow the twist of the rope no matter which direction you’re looking at it from, and the twist looks the same from both sides, so both workers would agree which direction to coil it.
Sure, the coil would appear to be clockwise to one and counterclockwise to the other, but the question isn’t whether “clockwise” looks the same from all directions. It doesn’t, but the word still exists. It’s just a theory, but I still bet rope work would have led to a word for clockwise.
So, both workers see that the rope is right-handed, so both workers agree that it should be coiled clockwise, so one worker coils it clockwise and the other coils it counterclockwise, but they’re both right because those are the same direction? I can’t see where the disconnect is, here.
“both workers agree that it should be coiled clockwise.” No, they agree it has to follow the twist of the rope. It will appear clockwise to one, counter clockwise to the other, but it follows the twist to both observers.
I don’t know what you’re getting at. I wasn’t disagreeing with your post, it just made me realize how ropemaking could have spawned a word for clockwise. I don’t know that it did, but it dawned on me that the most basic principals of rope work have two avenues for coming up with a word for clockwise.
I still don’t know what you’re getting at. It seems like you’re trying to get me to say the coiling is relative? It is, and I’ve said that three times.
To begin with I said:
Ok, that one just implied it was relative. I didn’t expect it to turn into a multi-day issue or I would have gone into more detail.
Later I said:
I don’t know how that could possibly make sense if it weren’t relative.
Relative terms are still useful if there’s a known vantage point. We use clockwise every day because we know it means you’re looking at the face of the clock. In the case of coiling, it refers to one person with a rope laid in front of them. To anyone else, it’s relative. If they’re on the other side of the rope of the person doing the coiling, it appears counter clockwise. If they’re on the same side, clockwise.
When it comes to two people on either side of a spool, you don’t have to worry about it. You coil the rope in the direction of the twists, which are helical. To one, it will turn out to be clockwise, just like a single person working with a rope in their lap. To the other, it will appear counterclockwise, just like a person watching a single person working with a rope from… under that person’s lap I guess.
However, if a two-factor definition can be admitted, right-hand rule is either a rule about electrical field or a rule about right hands. Or a conspiracy of the IEEE logo.
No, it isn’t. You agreed that the direction would be described as “clockwise” from one side, and “counterclockwise” from the other side. You also said that the direction had to be clockwise. You haven’t stated how to reconcile these two statements.
