Today let’s talk about what stuff is made of.
I invite you to try something. Take a piece of paper or a lump of blu-tack or Playdoh and hold it with both hands in front of you. If you don’t have anything to do this, it’s OK, just imagine you are doing it; this is sometimes called a thought experiment and is popular amongst thinkers who don’t like getting their hands dirty, or philosophers as they are otherwise known.
Take the paper, or whatever it is you have in front of you, and tear or break it in half. Done that? OK now take one of those two pieces and set the other aside. Take that half and then tear or break that into half of itself. Take one of those pieces and then divide that into two. And keep going until you have to stop.
What have you got? A big mess and a very small piece the stuff that you started with in your hand or on your fingertip.
At some point the stuff you are halving becomes so small that it becomes difficult to see it and pick it up. It is still there of course. You might imagine if you were much smaller or had a big microscope that you could keep on going dividing the stuff into two again and again and again forever, right?
You would be wrong. Because at some stage you would get to lumps of the stuff that are so small that they cannot be broken in two.
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All stuff is exactly like this. It is made up of tiny little lego brick-like things that are so small we can't see them except when we are using the most powerful microscopes. They are known as _atoms_. Funny word, isn't it? It comes from a word in the Greek language, atomos, that means something like "can't divide them into smaller bits or cut them up". There are many different types of these brick-like atoms; in fact we have found 98 different ones in nature, we have created 20 or so man-made ones ourselves and there could be a few more left to discover and so the current total is 118.
I've heard that there are 2200 different types of Lego brick, but only the people who make Lego truly know the answer to that. Whatever the real number, our Universe only needs 98 types of atom to make everything you know around you. The floor you are standing on, the clouds in the sky, the air you are breathing right now, the food that you eat - everything is made of atoms. These different kinds of tiny brick-like things join up in many different ways to make bigger, but still very small to us, blocks in regular patterns. We will talk more about them another time.
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