Music Weather is a really important topic for many, many people. Most of us want to know if it's going to rain, for example, like it is today or if it's going to be a hot sunny day, we need to decide whether we need to take an umbrella like this or wear a hat or wear warm clothes. So knowing what weather we're receiving and predicting the future weather for the next day is really important for lots of people. For farmers it's particularly important because they're growing crops for the rest of us to buy vegetables and fruit and grains and that sort of thing. So they need to know very accurately how much rain has fallen and whether they will need to irrigate their crops and that sort of thing. And for people living in towns and cities like most of us do, we need to know if there are going to be floods. We need to know if the wind is going to get strong like it is just this minute, whether there's any danger to us, whether we should be careful because there might be flooded roads, that sort of thing, or maybe even our houses can get flooded. So knowing the amount of rain is one of the components of weather that we need to be able to measure. Now when we're measuring rain you might think straight away, well, the units we're going to use are units of volume because rain is a liquid and we measure liquids generally using units like milliliters and liters because that's how we measure liquids. But when it comes to the rain we're not going to measure the volume simply because there's a lot of rain falling all over the ground. So I'm standing under one umbrella, there's a certain amount of rain falling on the umbrella. But there's a lot more rain landing all around me in other areas. And to measure the volume we would have to know how big an area we're measuring the rain over. So instead of that we measure how deep it is. So just like you might stand in water in a swimming pool and work out where the water comes to on your body and think whether it's deep or shallow. We want to do the same sort of thing with rain and we want to measure how deep the rain is on the ground. Now of course because most land is not flat we can't just put a ruler on the ground and see where the water comes to because the water runs away downhill. Just like it is where I'm standing on my driveway the rain is running downhill continuously. So even though we're getting lots and lots of rain today it won't stay here where I'm standing. So to measure it we need to capture the rain and then measure the depth. So I'll just hold this up. This is an example of what we call a rain gauge. So this is for measuring rainfall. It's the shape of a cylinder and the rain falls in the top and is collected inside. And then we can measure inside the cylinder how deep the water is. Now there's another part to this and that is that measuring depths in millimeters is quite difficult because they're very small measures. And if we want to be truly accurate it's going to be difficult to do that with just a standard ruler in a cylinder. So the makers of rain gauges like this one have come up with a clever solution. They have a funnel. So if you look at that you can see it's wider at the top and there's a small hole in the bottom. So there's a nice big area to catch the rain and then it's funneled through the funnel into a small tube inside the big tube. And so the small tube captures the rain but you can tell that the rain will come further up the tube than it would if it was just landing in a normal straight cylinder. And that's because the opening on the funnel is much wider. And then if we get lots of rain like we do today and it goes over that measurement it will overflow the small tube and go into the big tube. So I'm going to go and put this back out in the weather, out in the rain so I can capture the rain for today. And by tomorrow morning I'll come out and I will measure using the markings on the tube how much rain we have received today.