Brian Clegg

body, your body, to explore the most extreme aspects of science. It’s all there. Everything from the chemistry of indigestion to the Big Bang and the most intractable mysteries of the universe is reflected in that single, compact structure. Your body will be your laboratory and your observatory.
You can look at the whole body, treating it as a single remarkable object. A living creature. But you can also plunge into the detail, exploring the ways your body interacts with the world around it, or how it makes use of the energy in food to get you moving. Zoom in further and you will find somewhere between ten and 100 trillion cells. Each cell is a sophisticated package of life, yet taken alone a single cell is certainly not you. Go further still and you will find complex chemistry abounding – you have a copy of the largest known molecule in most of your body’s cells: the DNA in chromosome 1.
Continue to look in even g

traditional numbers become clumsy; a typical adult is made up of around 7,000,000,000,000,000,000,000,000,000 atoms. It’s much easier to say 7 × 1027, simply meaning 7 with 27 zeroes after it. That’s more than a billion atoms for every second the universe is thought to have existed.
There’s a whole lot going on inside that apparently simple form that you see standing in front of you in the mirror.
On reflection
In a moment we’ll plunge in to explore the miniature universe that is you, but let’s briefly stay on the outside, looking at your image in the mirror. Here’s a chance to explore a mystery that puzzled people for centuries.
Stand in front of a mirror. Raise your right hand. Which hand does your reflection raise?
As you’d expect from experience, your reflection raises its left hand.
Here’s the puzzle. The mirror swaps everything left and right – something we take for granted. Your left hand becomes your reflection’s right hand. If you close your right eye, your reflection closes its left. If your hair is parted on the left, your reflection’s hair is parted on the right. Yet the top of your head is reflected at the top of the mirror and your feet (if it’s a full-length mirror) are down at the bottom. Why does the mirror switch around left and right, but leave top and bottom the same?

The book in the mirror is printed in mirror writing, swapped left to right.
The reflected book is as far behind the mirror as my book is in front of it.
The book’s colours are the same in the mirror as they are on my side.
The front cover of the book in the mirror is the back cover of my book.
Just take a look at that last statement. If I simply consider the book in the mirror to be an ordinary book then, as I look at it, my book’s back cover has become the mirror book’s front cover. Lurking here is the explanation of the mirror’s mystery. It doesn’t swap left and right at all. It swaps back and front.
In effect, what the mirror does is turn an image inside out. The back of my book becomes the front of the book in the mirror. Put the book down and look at your own reflection again. Imagine that your skin is made of rubber and is detachable. Take off that imaginary skin, move it straight through the mirror and, without turning it round, turn it inside out. The point of your nose, which was pointing into the mirror is now pointing out of the mirror. The parts of you that are nearest the mirror are also nearest in the reflection. Your entire image has been turned inside out.
In reality there is no swapping of left and right, so you don’t have to explain why the mirror handles this differently from top and bottom. The reason we have the illusion of a left-right switch is down to your brain. When you see your reflection in a mirror your brain tries to turn the reflection into you. It makes a fairly close match if it rotates you through 180 degrees and moves you back into the mirror.

scope, use that, but otherwise use a magnifying glass.
That strand of hair is going to start us off on everything from philosophy to physics. Dubious about just how philosophical hair can be? Consider this: you are alive and that hair is an integral part of you (or at least it was until you pulled it out). Yet the hairs on your body are dead – they are not made up of living cells. The same is true of fingernails and toenails. So you are alive, but part of what goes to make ‘you’ is dead.
Remember that next time a TV advert is encouraging you to ‘nourish’ your hair. You can’t feed hair. You can’t make it healthy. It’s dead. Deceased. It has fallen off its metaphorical perch. Worried that your hair is lifeless? Well, don’t be. That’s how it is supposed to be. It’s quite amazing just how many hair products are advertised us

Infinity, as no end of people will tell you, is a big subject. It will take you into history, philosophy and the physical world, but is best first approached through mathematics. It makes sense to ease into it via big numbers.

giving a lengthy number a name you seem to demonstrate your power over it – and the bigger the number is, the more impressive your ability. This is reflected in the reported early life of Gautama Buddha. As part of his testing as a young man in an attempt to win the hand of Gopa, Gautama was required to name numbers up to a huge, totally worthless value. Not only did he succeed, but he carried on to bigger numbers still.

By giving a lengthy number a name you seem to demonstrate your power over it – and the bigger the number is, the more impressive your ability. This is reflected in the reported early life of Gautama Buddha. As part of his testing as a young man in an attempt to win the hand of Gopa, Gautama was required to name numbers up to a huge, totally worthless value. Not only did he succeed, but he carried on to bigger numbers still.

100,000,000,000,000,000? EASY, THAT’S ACHOBYA.

It’s fine giving names to numbers we encounter every day, but how many of us will ever use this number?

One, pheomelanin, produces red colours. Blonde and brown hair colourings are due to the presence of more or less of the other variant of the pigment, eumelanin. This is the original form of hair pigment – red hair is the result of a mutation at some point in the history of human development.
As we become older, the amount of pigment in our hair decreases, eventually disappearing altogether. Grey and white hairs don’t have any melanin-based pigment inside. In effect they are colourless, but the shape of the hair and its inner structure has an effect on the way that the light passes through it, producing grey and white tones.

isn’t particularly obvious when you hold a single strand in your hand and look at it with the naked eye, but under a microscope it becomes clear that there is more going on than just a simple filament of uniform material. In effect your hairs have three layers: an inner one that is mostly empty, a middle one (the cortex) that has a complex structure that holds the pigments and can take in water to swell up, and an outer layer called the cuticle which looks scaly under considerable magnification, and which has a water-resistant skin.
On the end of the hair, where you have pulled it out of your scalp, there may be parts of the follicle, the section of the hair usually buried under your skin. The follicle is responsible for producing the rest of the structure and is the only part of the hair that is alive.
Dyeing to be attr