By Michael Carroll
Best-selling author of Science for Beginners

Introduction     Part 1     Part 2     Part 3     Part 4     Part 5

Preamble:

I'm told by our esteemed editor that a number of readers have written to complain about the first part of this series. "Who is this guy?" they ask, and, "What are his credentials? What qualifies him to write about science?"

Well, I'm not normally one to blow my own trumpet, but since so many people seem to be interested (or at the very least suspicious), I've decided to give you a little autobiographical information. Who am I? Well, I'm a full-time writer and part-time scientist. I studied for a time at the School of Life, but was suspended for skipping classes. Later, I enrolled in a parallel university and studied Quantum Mechanics and Quantum Plumbers.

Sadly, few of my great discoveries were ever officially recognised by the scientific community: I was not able to see as far as other men because giants were standing on my shoulders.

Amongst the many scientific papers I have had published are:
Preposterone – The Alcohol-Triggered Hormone That Makes Drunks Talk Rubbish
The Jiggle Factor – A Study Of Why Women Walk With Their Arms Folded

Lesson 2 – Atomic Physics:

Back in the old days, science was a lot simpler... There were four elements: earth, air, fire and water, as seen in the table below:

Everything imaginable (at the time) could be made by combining one or more of these elements: For example, Mud (E2Wa) was made of two parts Earth to one part Water. The chemical symbol for rain was A10Wa (ten parts Air to one part Water). Hot water was simply Wa3F (Wa2F if the water was really hot).

But then electron microscopes were invented, and all of a sudden scientists realised that they'd been wrong. There are in fact many elements, such as Lithium.

All of the elements – at last count there were over a hundred – consist of atoms made up of at least one proton, at least one electron, and at least one neutron. Except hydrogen, which is so tiny there isn't any room for a neutron. It has one electron and one proton. This is not the only thing that distinguishes hydrogen from all the other elements: because hydrogen atoms are so tiny, hydrogen is very light and makes an ideal filler for airships. However, hydrogen is highly flammable, which is why these days airships are made out of asbestos.

The neutron (named in honour of the physicist Sir Isaac Neutron, inventor of gravity) is pretty much the stable part of an atom. Think of an atom like a swingball set: the electrons are the tennis-ball-on-a-string part, and the neutrons and protons (known as the nucleus) are the pole bit. The electrons swing around the pole bit in a more or less fixed orbit, until they encounter the bat (which in atomic terms could be radiation, or other stuff).

Now, atoms can be combined to make what we call molecules. Water, previously thought to be an element all of its own, is a molecule made up of two hydrogen atoms for every oxygen atom. Now, I know what you're thinking: hydrogen and oxygen are both gases, and both highly flammable. So, (a) how come water is a liquid and (b) why doesn't it burn?

Atoms come in two flavours, stable and unstable. They also come in a variety of sizes: the more electrons and suchlike, the bigger they are. For various reasons that I won't go into here, the electrons of an atom have orbits that you can think of like a series of Russian dolls: each one inside another, except for the outer one. The smallest doll (not counting the really teeny one that you can't take apart) is the innermost shell: it has only enough room for two electrons to spin around without hitting off each other. Further shells have room for more electrons.

Now, if an atom has less than the required number of electrons to fill its outermost shell, it's considered to be unstable: it needs electrons. This is known as the "vacancy" of an atom. Hydrogen needs one electron to make it happy: oxygen needs two. Thankfully, atoms are designed to share electrons whenever they can. So, two hydrogen atoms can share their electrons with an oxygen atom. For a more precise description, please see my textbook The A-Z of Physics, volume 3 (H to O).

So, we now have a water molecule... As you might guess, it doesn't burn because it's now quite stable, but why is it a liquid? Well, I wish I knew that. It's a bit beyond my knowledge. Even the greatest scientists in the world have a hard time figuring out liquids. We know that every element can exist in any of three states: solid, liquid, or gas. Their state depends on the temperature: Mercury is a metal, but at room temperature it's a liquid (and it's not the only one – ten points to whoever can name the other one, because I forget it at the moment). Iron is also a metal, but at room temperature it's solid. Heat it up, though, and it becomes liquid. Heat it up even further, and it will become a gas.

This is true for every atom, and pretty much every molecule with a few notable exceptions, particularly wood, which won't turn from a solid to a liquid – it'll just burn, which is a real shame because liquid wood would be very handy (there is also liquid paper, but that's just a brand name and it doesn't count). Now, this whole "solid to liquid to gas" thing can be confusing. Let's take concrete for example. You put the ingredients into a cement mixer, mix them up, and you have a liquid. Heat this enough and it turns into a solid. Heat it more, and it'll turn into a liquid! Weird, isn't it?

If you recall, you'll see that above I said "at last count there were over a hundred" elements. What do I mean by "at last count"? Well, the fact is, it's quite simple to create new elements (in theory). Add more protons and neutrons to an atom's nucleus and all of a sudden it'll start looking for electrons – and taking them from wherever it can find them.

Creating these new atoms is a time-consuming process, so scientists use particle accelerators to speed things up. Think of a particle accelerator as a kind of bobsleigh run. At the finish line is the target atom. If you're going to try this at home, it's best to use one of the heavier elements, as they're a lot bigger and therefore easier to hit. Put a proton at the start line, and give it a push. Ideally, it'll charge down the bobsleigh run and collide with the target atom, bonding with it. The more protons you add, the more electrons it'll need – but don't worry: atoms are reasonably self-sufficient and are generally capable of finding their own electrons.

Here's an interesting fact: A lot of the heavier elements don't actually appear in nature! They've been totally man-made! That's why they have such interesting names – the scientists who make them are allowed to name them. Some are named after places (americium, californium, europium, belgium), others are named after people (einsteinium, mendelevium, lawrencium of arabium). I once proposed the name "equilibrium" for a stable element, but it was rejected by the rest of the scientific community for being too clever.

Interestingly, some of the more recently proposed names seem to perfectly match the career of the average scientist: honorarium, opium, pandemonium, sanatorium, tedium and crematorium.

So, in conclusium – I mean, in conclusion – that's pretty much all you need to know about atomic physics. Everything is made up of subatomic particles known as protons, neutrons and electrons in a variety of combinations. Some elements are less stable than others, while some are not.

You should also be aware that there's another level to all this – quantum physics. I don't have any room to go into this right now, which is just as well because there aren't many people bright enough to understand it. Me included.