About half a century ago I saw a Cartoon in Punch at the Central Library of IIT KGP.
The first picture showed a kid teasing a centipede in his garden. The second showed the centipede winding itself into a tight spiral. The third showed the kid kicking the rolled up centipede. The last showed the thing rolling fast along the ground, with the kid shouting:
"Wheel!"
So, it is not true that wheel is a human invention as is commonly claimed:
"...The oldest wheel found in archeological excavations was discovered in what was Mesopotamia and is believed to be over fifty-five hundred years old...."
...http://inventors.about.com/od/wstartinventions/a/wheel.htm
Of course most every heavenly body spins, but to convert this spin into rolling, one requires a solid ground with friction, which may be available only on planets like our earth. Or no?
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But what about the screw?
I don't know if Mother Nature had invented the screw long before man did.
The human body has any number of joints of several varieties but apparently no screws are needed to work them. Of course if crucial bones fracture, I am told that stainless steel plates are screwed up to keep them in place.
Rinku, the naughty daughter of RSS, used to say of anyone searching for anything on the ground in the dark:
"Uncle, unka screw gir gaya lagtha!"
The seashells we see on the seashore (repeat: "she sells seashells on seashore" quickly again and again) may be Nature's mimicry of our screws whose feature is a helical groove.
As a student in Pre-University I was fascinated by the figure that showed the screw as nothing but the inclined plane; just roll it around your pencil.
Getting the screw gauge formula was easy enough but that of the Vernier Calipers was always a mystery...the explanatory diagrams worsened it.
Till I encountered a spectrometer in the Third Year Lab at KGP that had a negative-reading Vernier: it had its main scale divisions shorter than its Vernier's. I mean, instead of 9 msds coinciding with 10 vsds, it was the other way round. It was fun to figure out how to use it. I am sure it was put in the students' lab just to make them learn how a Vernier Calipers works.
It is funny that we learn to think when we are forced to, by a ridiculous situation. For instance, we take for granted the 'angle of contact' of a liquid surface with glass on one side and air on the other by looking up Tables.
But to get the true measure of what the angle of contact does needs the viva question:
"What happens if you insert a capillary tube of protruding length 2 cm into a beaker of water for which the capillary rise is 4 cm?"
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Screws come in the left hand and right hand varieties.
One may ask: why?
One of the reasons is that when a right handed screw joins a thing that rotates clockwise, say, it will get loose and fall off (like Rinku says) in due course, unlike when it rotates anticlockwise. So, a left handed screw is to be employed in such situations (e.g. fan blades, cycle pedal).
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Talking of left and right handedness reminds of their absoluteness...I mean parity non-conservation and stuff for which the entire class of Chandra got their Nobels leaving the Dame in the lurch.
Also I read Feynman worried about the so-called left-right inversion by a plane mirror till he realized that a plane mirror doesn't so much invert right and left as it turns the viewer 'inside out'.
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It was a revelation to me in my student days to learn that the 'propeller' of Wright Bros is an 'air-screw'...give it to them, these goras are great inventors.
Take Stevenson's locomotive...just look up:
http://en.wikipedia.org/wiki/George_Stephenson
I read somewhere (it may be junk info) that mathematicians as usual jumped in and 'proved' that to-and-fro shuttling motion can't be converted into circular motion...till Stevenson came up with his design.
They are like that!
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Googling for 'screw' led me to Screw's Sulfur Spa in Dominica.
Apparently Screw is the nickname of its designer.
Funny, how folks get nicknames.
Sometimes the nickname becomes so popular that the original name is forgot.
In the 1960s, Alankar, the Students' Magazine @ KGP brought out a list of their teachers' names on the left and their nicknames on the right of a Table.
Like say:
'B. G. Chatterjee'...... 'Bum Chat'
'G. P. Sastry'..............'gypsy'
But there was this curious entry:
'Chotta Motta'.............'Ashrujit Mukherjee'
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Looking up for Dominica gave me a thrill:
"..The Dominican Republic (
i /dəˌmɪnSome sweet-sounding words there!
And sweeter mental imagery!!
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