I attended a couple of seminars this week- one by a colleague and another by a famous professor. They both talked about models in different fields. One of them gave an accuracy of 75% (work in progress), and was quite well received, while the other had an accuracy of 99.99%, and researchers asked if it was good enough.
People often think of science and engineering as synonyms. They are not. Science is all about understanding nature, or rather, reducing the complexity of nature into a small set of mathematical equations. It deals with 'pure' substances. A scientist's job is to- Look at nature, understand what it's doing, see if we can figure out a mathematical law, and see if this mathematical law is always valid (if there are exceptions, the cycle starts again), and maybe build a new material using this understanding. Engineering is about practical applications. A mathematical law cannot run a car. It is an engineer's job to use these laws 'sensibly', and build things that can be used in our daily life.
Consider this simple question: How long does it take for a ball dropped from a height of 10 metre to reach the ground? A high school student could probably answer this in less than half a minute. But, is it an answer from science, or was engineering included?
First, we assume laws of classical physics- big objects, low speeds: Fair enough. Next, we can use a simple kinematic formula: h = 1/2 *a*t*t, and calculate the time of descent. But, whenever we use this formula, we assume zero air resistance. Or rather, we assume it is negligible. This is an engineering approximation. Scientific accuracy requires that you account for everything, engineering accuracy lets you get away with small approximations. In fact, this assumption, that air resistance is negligible, is not always valid. If you drop the ball from 500m instead of 10m, air resistance becomes very important.
There are actually even more assumptions. We always neglect the earth's rotation, and the fact that the acceleration due to gravity decreases as one moves away from the earth's surface. We can include them in the calculation, but - engineering accuracy : neglect them. If you are doing this for a satellite, you can't ignore any of these.
Now, this may make engineers look like a bunch of lazy guys who just hate solving everything. Say, we want to account for the air resistance. How do we include it in the equation for time of descent? We can say that the drag force is given by an equation like 1/2*density*velocity*velocity*area*drag coefficient. But then, this equation is also an engineering approximation. The more exact equations to solve are what we call 'Navier-Stokes Equations'. These equations are so hard to handle, that there is a million dollar prize for proving that unique solutions exist to the equations. And we haven't even talked about the elasticity of the material of the ball, or the surface texture.
And, did I mention that the Navier-Stokes Equations are also based on an approximation called the continuity hypothesis? This is how hard a very simple problem would be if we do not use engineering approximations. An engineer's job is to figure out what approximations work, and use them to build practical stuff. That does not mean that science is not a big deal, it is. Scientific laws are the basics over which we make approximations. These laws give us confidence in our work. It is just that without approximations, even the simplest of problems become extremely difficult to solve (but not impossible, hopefully). Imagine what it would be like to calculate the thrust of a rocket engine without using any approximations.
People often think of science and engineering as synonyms. They are not. Science is all about understanding nature, or rather, reducing the complexity of nature into a small set of mathematical equations. It deals with 'pure' substances. A scientist's job is to- Look at nature, understand what it's doing, see if we can figure out a mathematical law, and see if this mathematical law is always valid (if there are exceptions, the cycle starts again), and maybe build a new material using this understanding. Engineering is about practical applications. A mathematical law cannot run a car. It is an engineer's job to use these laws 'sensibly', and build things that can be used in our daily life.
Consider this simple question: How long does it take for a ball dropped from a height of 10 metre to reach the ground? A high school student could probably answer this in less than half a minute. But, is it an answer from science, or was engineering included?
First, we assume laws of classical physics- big objects, low speeds: Fair enough. Next, we can use a simple kinematic formula: h = 1/2 *a*t*t, and calculate the time of descent. But, whenever we use this formula, we assume zero air resistance. Or rather, we assume it is negligible. This is an engineering approximation. Scientific accuracy requires that you account for everything, engineering accuracy lets you get away with small approximations. In fact, this assumption, that air resistance is negligible, is not always valid. If you drop the ball from 500m instead of 10m, air resistance becomes very important.
There are actually even more assumptions. We always neglect the earth's rotation, and the fact that the acceleration due to gravity decreases as one moves away from the earth's surface. We can include them in the calculation, but - engineering accuracy : neglect them. If you are doing this for a satellite, you can't ignore any of these.
Now, this may make engineers look like a bunch of lazy guys who just hate solving everything. Say, we want to account for the air resistance. How do we include it in the equation for time of descent? We can say that the drag force is given by an equation like 1/2*density*velocity*velocity*area*drag coefficient. But then, this equation is also an engineering approximation. The more exact equations to solve are what we call 'Navier-Stokes Equations'. These equations are so hard to handle, that there is a million dollar prize for proving that unique solutions exist to the equations. And we haven't even talked about the elasticity of the material of the ball, or the surface texture.
And, did I mention that the Navier-Stokes Equations are also based on an approximation called the continuity hypothesis? This is how hard a very simple problem would be if we do not use engineering approximations. An engineer's job is to figure out what approximations work, and use them to build practical stuff. That does not mean that science is not a big deal, it is. Scientific laws are the basics over which we make approximations. These laws give us confidence in our work. It is just that without approximations, even the simplest of problems become extremely difficult to solve (but not impossible, hopefully). Imagine what it would be like to calculate the thrust of a rocket engine without using any approximations.
