Perturbation theory comprises mathematical methods to find approximate solutions to problems in mechanics. Even though the only maths involved is the application of the three equations of motion and the Newton's Second Law statement (f=ma), it is impossible, in most real cases to find the exact solution to a problem in dynamics.
Case in point, the Coriolis force. Due to the earth's rotation, a body experiences a force that is proportional to velocity in a direction perpendicular to it's velocity. Consider a body freely falling at the equator from a reasonable vertical height, say a kilometre. Even with the usual, almost unreal simplification of assuming that air resistance is absent, it is impossible to find the exact position of the body, theoretically, when it reaches the ground. Here's why.
The Coriolis force acts on the body towards east, increasing linearly with the velocity. Now, the Coriolis force slightly changes the direction and magnitude of velocity, which again changes the Coriolis force, which again changes velocity. This goes on back and forth infinitely, and simply cannot be solved without an approximation.
We take care of the big force, the gravity. Then consider Coriolis force once only, assuming the effect of the force itself doesn't cause more perturbation. We find the deflection to be very small, and using this fact justify the neglect of the next order application of Coriolis force.
Ha!
Sounds like life doesn't it. You consider all the big factors. The ones that have the largest consequence. Try some smaller things. To a level. Justify avoiding other small tasks. Hobbies. So many things we can do but of little consequence. Do we have to do them?
The facts of the matter is the small factors, at least in mechanics, don't amplify, or consolidate the large factors. Instead, they perturb it. Actually come in the way of what would otherwise be smooth, neat, and mathematically elegant motion. With all associated mathematics straight-forward and explicit.
Life differs there though. The small things clear our minds. Refresh us. Allow us to elegantly perform the tasks higher on the priority list.
And those are two things I've learnt after joining university and beginning my life in hostel.
Not all analogies make sense. Not all analogies are true. There is no poetic brilliance in comparing anything to anything. The way my lectures assume you can draw analogies between large lorries trying to pass each other with electron clouds sterically hindering each other. Not everything goes, even in the liberal world of poetry and/or teaching.
Second, the small things are extremely crucial. The creative aspect is essential for clarity in thought. Without physical activity, something to transiently distract you from the burden you carry, sustained effort is nearly impossible.
Writing this blog gives me immense pleasure. And helps me study as well.
Win-win, no perturbations.