Arcturus peering through the clouds at night | Image copyright Graham Jarvis 2014, all rights reserved

Today I’m going to tell you about a star. Just one. Its not a particularly special star but there is a very good reason that I am going to talk to you about this star first, of all the many many stars in the sky. It is because it is easy to find. If we are going to to talk about stars in the night sky together I want to you to be able to look up and see what I am seeing. Even if you don’t know much about stars, I think I will be able to teach you how to find this one.

The name of this star is Arcturus. Funny name, isn’t it? All stars have names given to them by people who watch stars for a living but some stars have nick-names that are often very old. Arcturus means something like “bear-watcher”, in the Greek language. Why would a star watch a bear? Well it goes back to the days before television and street lights, when people had little to do in the evening but look up at the stars on clear nights. They imagined they could join the stars with lines (like a dot-to-dot puzzle) and draw shapes with them. Its the same as when you see a cloud in the sky that looks like something familiar. One shape high up in the sky they thought looked like a big bear. It also was in the northern part of the sky and north was the direction that Greek-speaking people knew bears lived. The star we are talking about, Arcturus, isn’t part of this dot-to-dot shape but is nearby - like it might be at a distance watching the bear-shape. So that is how it got its name.

These days we don’t see bears in our gardens quite so often and street lights make the night stars a bit harder to see and so the dot-to-dot bear shape is harder to notice. I am sure you have seen another shape up in the sky that we would both recognise. To me it looks like a saucepan and handle. To others it looks like an old-fashioned plough; the type that used to be pulled by horses on farm fields. Have you seen that shape before? It is called The Plough or The Big Dipper and is actually part of the nose and back of the big bear. Don’t worry if you you can’t see the whole bear - I still can’t make out all of it either. The Plough shape is often found high in the Northern part of the sky. I made a picture of the shape so you can look at the night sky and find it yourself one night:

So if that is the nose of the bear then where is the bear-watcher? It is not so far away. If you draw an imaginary curved line using the curve of the saucepan’s handle to guide you then you will find a very bright star a little distance away. People who like watching stars remember this way of finding it by saying they arc to Arcturus. Look at the dotted line curve on the diagram and follow it to the bright star.

Arcturus is the fourth brightest star in the sky. Two of the even brighter stars can only be seen in places much further south than where I live in England and so, for me, Arcturus is the second brightest star in my sky. The best time to see it is in the Spring and Summer.

I really hope that you get a chance to see it for yourself in your sky because I want to talk more about it another time and I want you to know that it is a real thing. Not something that someone made up in a story. But I will understand if you don’t get a chance to see it by the time I next write. If fact, the difficulties of being able to see the stars when you are young is what I will talk about next time.

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Julia's Engagement Ring | Image copyright Graham Jarvis 2014, all rights reserved

Last time we talked about stuff being made of Lego-like bricks called atoms. Just to be clear before we talk more, when I say atoms are like Lego bricks I don’t mean exactly the same as them. Real atoms are not actually Lego bricks. You know already that they are much much smaller. In some ways atoms can be sticky like Lego bricks and they can fit together in different ways, but in other ways they are different too. I’m using something you know about to describe something else that you don’t to help you to draw a picture in your mind. It is not always the best drawn picture, but knowing about Lego, as I’m sure you do, is still really helpful to understand how these atom things work and how reality is made, even though they are not exactly the same thing. All of the real world around you is made from these atoms, so it is worth trying to understand.

Let me tell you another thing about atoms using lego bricks to draw the picture in your mind. If you make something made of the same type of lego brick, for example if you made something from one hundred red square bricks, then it will be something that is made only of square red bricks. But the thing you make from those bricks won’t have to be square and blocky, though it will be red. You could build a tall tower from those bricks or small little blocks made of just two red bricks each or giant rings made of bricks. Some stuff that we see around us is just like this - made of only one type of atom and some people say it is made of just one element. As we said before we know of 118 different elements or different types of brick, in our not perfect Lego illustration.

A good example of an element is a precious diamond. It is made up of just one type of small little atom. Each atom-brick is closely joined to all of its neighbours which is why a diamond is very hard stuff indeed - in fact one of the hardest things there is. Another example is the metal gold. Gold atoms don’t join well with other types of atom and so they are often found joined together having a private party on their own. This is also why gold things stay golden and shiny for a very long time when other things made with different more friendly atom-bricks will change. For example, iron goes rusty because iron atoms quite easily join up with oxygen atoms in the air to make rust; which is something made of both types of atom. We will talk more later about stuff that is made from more than one type of element.

So the picture at the top of this post is the diamond engagement ring I gave to my wife on the day I asked her to marry me. And now you know that it is mostly made up of just two types of atom-brick. Don’t tell her that though she might feel a bit cheated.

In the real world, just as in the box containing your Lego bricks, things are rarely that simple or ordered. Most of the stuff you can see around you is made up of many different types of atom bricks joined together in repeating patterns that create similar looking bigger blocks. These blocks are called molecules. Most things are made of molecules. We will talk more about them next time.

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Today let’s talk about what stuff is made of.

Cuckoo Spit In June | Image copyright Graham Jarvis 2014, all rights reserved

What is cuckoo spit? The answer isn’t the spit of a cuckoo. It is something much more interesting.