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Science and Engineering

August 10, 2015

Previously, as in maybe 100+ years ago, “science” was important and the importance of it vastly exceeded the importance of engineering.  Today, I believe that trend has changed and the discipline of “engineering” is probably more important.  But, I am of the believe that engineering is at least the stepchild of science and you can’t ignore scientific discipline any more than you can ignore gravity.

Engineering, in layman’s terms, is the practice and discipline of making things that work, making things that aren’t working work, and the skills and abilities to be able to convert someone’s theory into practice.  This is certainly concerned with science but is more practically grounded.  In today’s world the distinction is important.

One of the key aspects of this is the motivation of the scientist is always “Why?” whereas in general the engineer isn’t really concerned with why or why not but just getting the thing working.  Out in the desert with a non-working car the scientist is going to be stuck on the point of trying to figure out where the water in the cooling system went and while he might have some interesting theories about where you could find water in the desert, the engineer is going to be focused a lot more firmly on both getting something into the cooling system and that it stays put.  The idea of using a children’s fruit drink isn’t going to occur to the scientist – its not water, remember – but to the engineer the sugar in the drink might just be the ticket to sealing up the leak.

McGyver is certainly not a scientist but he is the 1980s answer for engineering.

Over the weekend I made a big mistake; once again I watched the movie “The Core”.  This came out over 10 years ago and, as far as I know, has never been equaled in its mistakes, gotchas and distortions.  One of my least favorite lines is where one of the “scientists” in explaining to someone that all science is “best guess” and nobody really knows anything.  This might be a cute line for a post-modernistic movie tailored for an audience that believes science has given them nothing but Agent Orange and Tang but shows a disturbing lack of education.

Part of the annoyance of watching the movie is that for the entire 135 minutes there is about one silly thing every minute or so.  There are plenty of web sites that talk about the “bad science” of this movie, so many that there is no need to repeat the litany of wrong-headedness that pervades this movie.

The tie-in with this post is early on in the beginning of the movie we see pigeons crashing through big windows in tall buildings.  Now a “scientist” might be able to come up with a plausible theory how this is possible, but from an engineering perspective it is incredibly silly.  I did a very small amount of research on this last night and discovered the phrase that tempered glass is a pretty old technique and one that has been superceded by a number of other ways to make higher strength glass.  But even tempered glass in a 1/4 inch thick window glass form requires an impact of around 10,000 PSI to punch through it.  With a hammer, what you need is 10,000 pounds of force (better expressed in something like neutons, but I’m trying to stick with what I have) to break such a window – not impossible with a 1-pound hammer with about a 1/4 inch striking surface and a good swing at the window.  This is assuming the hammer is tilted somewhat when striking the window – if the head of the hammer was perfectly perpendicular to the glass the striking force would be distributed over a larger area and require even more powerful a swing.

OK, so what about a pigeon?  Your average pigeon is 9-13 ounces in weight, and the top of its little head might be at most 1 square inch in area after some initial mashing occurred.  So could a pigeon create a 10,000 PSI impact into a glass window?  I am NOT going to get into the full depth of the mathematics here to prove such a thing is impossible, but I am going to say that it would require the pigeon be flying over 100 MPH at the time of impact.  Highly doubtful.  I don’t think you could break a modern building window with a pigeon even if it was fired from a good-sized air cannon at over 100 MPH.  One of the key aspects of this is the little pigeon body has far less resistance to impact forces than the glass.  So even if you has sufficient acceleration of the pigeon, the pigeon would be pulped rather than actually breaking the glass.

Could you break the window with more pigeon impacts?  Say, 100 pigeons striking at the same time?  Dividing up the force required by 100 would certainly change things some, but still we are talking about 100 pounds of pigeon needing to develop far more than 10,000 pounds of force because it is spread over a much larger area.  The end result is 100 pigeons become a sticky mass of pulped pigeon and the window remains intact.

This commentary on pigeons can also be applied to the 1963 Alfred Hitchcock classic “The Birds”.  Although we are dealing with small window pane glass or the glass in a telephone booth, still the mismatch between bird structure and glass structure leads one to the inescapable conclusion that the birds simply do not have sufficient mass or cohesiveness to effect damage on virtually any size piece of glass.  At least for birds the size of pigeons or smaller.  Now, if you want to talk about bald eagles going up against a window the size of the bird itself, well, we are talking about a whole different sort of scale here.

Here is where the engineering discipline makes a significant difference.  A scientist is likely to focus on mass-on-mass impact and come out with a lot of equations showing that at 1027 MPH a pigeon can penetrate a large office building window.  The engineer is far more likely to note very early on that one reason pigeons do not fly over 30-40 MPH is because their wings would tear off.  Similarly, upon impact with any hard surface the less cohesive mass is going to come apart and distribute the impact energy over a much larger area.  There is little question that a pigeon is less cohesive than a big glass window.

So rather than expressing the problem as a purely mathematical one that has a solution – all it takes is a big blackboard – the engineer can get right to the heart of the question and say all the math is pointless because the pigeon comes apart.

This is the difference between the scientist and the engineer.

I would happily further this discussion with people that want to refute this or confirm it.

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