Engineering Physics

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In response to the post: Negligence:

http://gpsastry.blogspot.com/2011/12/negligence.html

Pratik sent me the following delightful Dirac Quote:

"The system of approximations I shall use will be somewhat similar to the approximation that engineers use in their calculations. Engineers have to get results and there are so many factors occurring in their problems that they have to neglect an awful lot of them; they don't have time to study everything seriously and they develop a sort of feeling as to what can be neglected and what can't. I believe that physicists will have to develop a similar sort of feeling as to what can be neglected and what can't. The final test is whether the resulting theory is coherent and is in reasonable agreement with experiment."

...P. A. M. Dirac (1966)

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Remember that Dirac trained as an Electrical Engineer, held the Lucasian Chair of Mathematics at Cambridge, and won the Nobel in Physics...some combo!

Coming to the 'feeling' Engineers develop and ignore hi-fi Physics and Mathematics, Feynman said a mouthful. He was talking to a Mechanical Engineer and receiving instructions:

"...when you have a gear ratio, say 2 to 1, and you are wondering whether to make it 10 to 5 or 24 to 12 or 48 to 24, here's how to decide: You look in the Boston Gear Catalogue, and select those gears that are in the middle of the list. The ones at the high end have so many teeth they're hard to make. If they could make gears with even finer teeth, they'd have made the list go even higher. The gears at the low end have so few teeth they break easy. So, the best design uses gears from the middle of the list."

Great lesson from a Military Engineer to a Quantum Freak!

During the British Rule, 'Engineers' meant only Civil Engineers trained to build Roads and Bungalows (still called R & B), bridges over rivulets, anicuts and railroads. This is because the British, unfortunately, couldn't import Roads and Buildings and Bridges from England and charge Indians for the same. They didn't bother to train Mechanical Engineers because simple machines like nail-files and razors could easily be imported from Home Sweet Home.

The Faculty Hostel I lived in at IIT KGP for 7 long and eventful years was named after the Engineer Supreme of British India, Visvesvarayya, (they knighted him...he lived a 102 years and also won the Bharat Ratna). The name was not unfamiliar to me because when I joined my AU at Waltair (Visakhapatnam), my MD Uncle took me to its famous natural harbor and pointed to what looked like a dead and floating giant whale and asked me to guess what it was. Even then I was a follower of Lincoln's Precept and fell silent. And then he triumphantly told me the answer: "It is the deck of the ship loaded with cement bags by Visvesvarayya who sank it at the mouth of the narrow sea-creek entering the harbor sandwiched between two verdant hills."

That is what precisely Dirac calls 'feeling' of great Engineers. The mouth of the creek was too turbulent and ships trying to enter the harbor were buffeted and bashed and shattered before they appealed to our Visvesvarayya. I don't think he would have hit upon his novel solution if he were merely trained at IIT KGP (or worse, IIT Cawnpoor) where rumor went that they teach: "Stress tensor is symmetric", and let it go at that ;-)

My friend NP (who rose to the position of DD at KGP) told me the following (spurious) Q & A Session that went on in his first Interview for the position of the exalted Assistant Professor in ME:

Q: What will happen if a 10-ton crane is loaded with a 20 ton boulder?

A: The stresses developed would no longer be within the elastic limit

Q: That is not the answer expected of a Mechanical Engineer

A: The strains in the cables would be outside the designed range

Q: So what???

A: They will SNAP!!!

Q: Precisely! You are selected...


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