Why is carbon more abundant than gold in the universe, and where do these substances come from? This question will hopefully be answered by the end of this section concerning the building blocks that make up the entire universe. Understanding these basic units allows us to manipulate their properties to advance our technologies and cater them to our ever-changing needs. Everything, from the smallest computer chip in your iPod to you to the largest galaxies in the universe, is comprised of what we now call atoms. The study of atoms and their behaviours has led to some very interesting and useful discoveries, without which there would not be an iPod at all. Peruse this section and learn about the basic constituents of that tree you can see from your window, as well as yourself!

If you were asked to imagine an apple, including how it behaves, what it looks like and its size compared to other objects you would have very few problems. This is mostly because, although we don’t really realise it, an apple is of the same order of magnitude as the world we regularly interact with. It’s also easy, for instance, to visualise a computer or another human being. Trying to imagine a single grain of sand or the sheer scale of mountains compared to ourselves is far trickier. This is the reason why our imaginations have such a difficult time comprehending the scale of the universe, for example, or the size of an atom.

The average atomic radius is of order 10-10 m, a million-billion times smaller than the scale on which we generally see and interact. While the size of our galaxy, the Milky Way is on the scale of 1020 m, more than a billion-billion times larger than us. These huge differences make understanding the concepts of the workings of these objects difficult. It also means that observing them in order to further our understanding is hard and requires complicated instruments. Atoms can be observed using a scanning tunnelling microscope, and can even be moved into patterns. However, operating this sort of machine is similar to trying to build a house of Lego while wearing boxing gloves. The difference between our scale and the scale of the atoms makes studying and manipulating them a real challenge. On the larger scales, the sheer distance of billions of light years to other galaxies makes observing them and interpreting what we see highly difficult.
In order to make working with such large and small numbers slightly easier, we have a naming convention, shown below, for the different orders of magnitude. Wavelength, for example, is usually quoted in nanometres, or distances to astronomical objects in megaparsecs.

Name The Number Prefix Symbol
trillion 1,000,000,000,000 tera T
billion 1,000,000,000 giga G
million 1,000,000 mega M
thousand 1,000 kilo k
hundred 100 hecto h
ten 10 deka da
unit 1    
tenth 0.1 deci d
hundredth 0.01 centi c
thousandth 0.001 milli m
millionth 0.000 001 micro µ
billionth 0.000 000 001 nano n
trillionth 0.000 000 000 001 pico p

You may think that on such different scales there cannot be a connection between atoms and galaxies. However, scientists have fairly recently realised that you cannot fully understand the processes within a galaxy without understanding what it’s made of at the most basic level of atoms and smaller. Nuclear physics in particular spans the great divide of the scales, as you will see in a later chapter concerning stars and the critically important process of stellar nucleosynthesis.
We will now go on to look at the matter that makes up everything we see in more detail >