Monday, June 25, 2007

This Blog is Back Online!

School re-opens today. Haha. Hope you guys had a good day in school, but, in other news, this blog is back! Let's begin with something light.

I'm not sure if you've ever wondered how physics is organised: how is it broken down into different categories, and how is physics taught in general? Actually, from the lessons you've had so far, you should probably have a rather good idea of how some of this organisation is done. You have encountered one important branch of physics already: optics, or the study of light.

Actually, the physics that you will be learning for the most part is known as classical physics, or physics that was thought to be correct up till the start of the 20th century. Yes, I know it can be quite upsetting to hear that the physics that you are learning now is "incorrect" (actually, a sizeable portion of it still stands, but a significant number of important facts that you are taught are in fact either outrightly incorrect, or are approximations of something more correct), but what is taught gives correct results in every day experiments.

Classical physics can be divided into three really gigantic groups: classical mechanics, electromagnetism and thermodynamics.

As an indication of how gigantic and complex classical mechanics is, the things that you are learning now constitute what is known as Newtonian mechanics: so all the kinematics stuff, Newton's laws, energy work and power etc. fall under Newtonian mechanics. Mechanics is a study of motion, whether it is the motion of a point particle (particle mechanics), a ball (mechanics of many-particle systems), a rotating disk (rotational mechanics), two galaxies colliding (celestial mechanics), a sound wave or air over an aerofoil (fluid mechanics).

In itself Newtonian mechanics is riddled with complexities, but, can you believe it, mechanics has been reformulated twice into Lagrangian mechanics and Hamiltonian mechanics. These are basically different versions of mechanics that can be used in more rigorous and complex ways, that are fundamentally the same as what Newtonian mechanics says.

Electromagnetism is the study of electricity, magnetism and their combined phenomena, e.g. electromagnetic waves. Optics actually falls under this category, but at our level, we treat it like a typical wave. Electromagnetism is essentially a study of charges and the kind of effects associated with stationary (electrostatics) and moving (electrodynamics) charges. Charged particles also produce electric and magnetic fields, and the study of the interaction of these two fields with each other is an integral part of electromagnetism.

Thermodynamics is a study of how large systems of particles (with too many particles to account for one by one: think of how many particles there are in one mole!) respond to changes in their surroundings. This branch of physics deals with heat, temperature, pressure and volume, and is an attempt to describe a huge and complicated system with each an every particle in the system behaving differently with simple laws. An important mathematical tool here that is not commonly found in the other two classical disciplines is statistics. In statistical mechanics (a very closely related field to thermodynamics) is the physics of linking microscopic properties of the atoms and molecules, like energy and velocity of each particle, to macroscopic properties of the whole system, like temperature, pressure and volume.

These are the three main branches of classical physics: you will find that Sec 3 will deal mostly with mechanics and optics, while Sec 4 will deal with thermodynamics and electromagnetism, plus a little bit of modern physics.

So if classical physics is "classical" and rather out of date, what is modern physics? And how is it organised? Curiously, you'll find that topics in classical physics tend to overlap each other, even at the fundamental level, but modern physics can be clearly divided into two: Relativity, the theory that deals with everything gigantic, and quantum mechanics, which deals with the minute. Of course, they do overlap, resulting in (dear God) relativistic quantum mechanics, which I don't pretend to understand in the least bit, but there is at this moment some conflict of interest going on between quantum mechanics and relativity. You will, of course, deal with a little bit of quantum mechanics in Sec 4, but don't be afraid, it's really simple stuff: just an introduction to radioactivity.

If you do a little bit of reading about classical physics, you will realise something interesting about each of the three categories: they have a set of laws governing each, and interestingly, there are four most most fundamental laws for each of the three main categories (they are: Newton's three laws and his law of gravitation for mechanics, Maxwell's Equations of Electromagnetism (there are four) for electromagnetism, and the Laws of Thermodynamics (from zeroth law to third law)). Don't think that they are distinct and separate: they overlap on many occasions, and indeed, their unification is one of the driving forces behind the advancement of physics as a science.

Indeed, if there's one thing you should realise, now that you know the categorisation and all, it is that each category is governed essentially by a few very simple laws that can give rise to many results. Please, do check out the fundamental laws that I've listed out for you earlier, and then appreciate this fact that I've quoted from a book as you study this science. This is why I constantly tell you guys there's no need to study for physics!

"Applying the laws of physics can give rise to challenging problems whose solutions call for clever insight and mathematical agility. The challenge of problem solving is what gives physics some of its intellectual interest and also its reputation as a difficult subject. But if you approach this course thinking that physics presents you with numerous difficult things to learn, you're missing the point. Because it is so fundamental, physics is inherently simple. There are only a few basic laws to learn; if you really understand those laws, you can apply them in a wide variety of situations. We wrote this book in a spirit that emphasises the underlying simplicity of physics by reminding you how diverse examples are really manifestations of the same underlying physical laws. You should come to understand the basic laws thoroughly so you can apply them confidently in new situations. As you read the text and work the problems, remember the simplicity of the underlying physical principles. Ask yourself how each problem you approach is really similar to other problems and to the text examples. And you will find that similarity, because the many problems and examples really do involve only a few underlying laws. So physics is simple - challenging, too - but with an underlying simplicity that reflects the scope and power of this fundamental science." - Physics For Scientists and Engineers, Wolfson & Pasachoff.

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