Nature creates round objects all the time (stones in a river, a hedgehog in a ball,…), but the principle of an axle is not found as far as I know.
Nature creates round objects all the time (stones in a river, a hedgehog in a ball,…), but the principle of an axle is not found as far as I know.
yep, i don’t think there’s basically any living organism that is made of two parts that are not solidly attached to another, sothat they can rotate against one another.
knee joint might come to mind, but that’s also connected by collagene i think, so it can’t rotate by more than 360°.
Wikipedia has a whole article on this subject:
https://en.wikipedia.org/wiki/Rotating_locomotion_in_living_systems
The exceptions it mentions are bacterial flagella and part of the digestive system of some bivalves.
yeah thanks for the article! rotating bacterial flagella is what came to my mind as well, but it’s microscopically small (i think the flagella is a single macro-molecule?) so i’m not sure whether to include it in the list of (macroscopic) “mechanical rotation”… it’s more like biochemical mechanical rotation.
if we go for biochemical mechanical rotation, there’s more: ATP-Synthase is a molecule that sits in cell membranes and that rotates as well each time that a proton passes through it.
I think the bivalve style is the more interesting case—it’s like their guts have a built-in mortar-and-pestle.
If your knee can turn 360°, you should talk to some scientists, so that they can study you.
Rotating is in nature, but as you said: always with a maximum rotation, never free without limits.
How about this insect with a pair toothed gears? Not an axle, but still amazing!
it’s gears, alright, but i don’t think that it can rotate by more than 360°?
No, that’s what I meant by not an axle.
But, come to think of it, we can swing our arms round and round, more than 360°.
I would argue that’s more due to the up-down and front-back limited rotations combining to form a circular mode, kinda like a Cartesian to Polar coordinate mapping
that’s reasonable.
bonus fun fact - the etymology is connected - “axle” comes from older words for “shoulder”, or “armpit”, which survives in some regional Englishes as “oxter” - the connection is apparently that you’d carry a person by putting their arms up and linking at the shoulders, much like an axle is how wheels carry a cart.
https://www.etymonline.com/word/axle