����ý

When you wake up in the morning, one of the first things you might notice is the light peeking through your curtains. This light comes from the Sun.

So, what is the Sun and why is it so important?

Well, the Sun is a star, a swirling ball of glowing gases. It looks a lot bigger than other stars, the ones we see in the night sky, because it is the closest star to us, 150 million Km away.

Its temperature in the centre is around 15 million°C.

The Sun gives off energy which we experience as heat, light and ultraviolet light, a kind of energy that you can’t see or feel.

We can feel the Sun's heat, especially on a clear summers day - when it's warm enough to wear a t-shirt without jacket. Even in winter, the heat from the Sun can melt the snow or ice on your street.

The Sun's light helps us to see clearly, even on cloudy days! It also helps us know what time of day it is; we get up in the morning when the Sun's light is bright and go to sleep when we can't see the Sun's light anymore.

Ultraviolet light is what can cause us to have a suntan, or sunburn if we’re not careful! We can protect ourselves from the Sun's ultraviolet light by applying Sunscreen that stops it getting into our skin and by limiting how much time we spend in the direct sunlight.

The Sun affects all of our weather.

The heat from the Sun can make our days hotter. We feel it most in the middle of the day when the Sun is shining down on us more directly from overhead.

The heat also evaporates cloud and fog - turning them from drops of liquid water into water vapour, an invisible gas. That can make for a clear, lovely day.

So, when you feel the Sun hitting your skin on a nice summer’s day, remember where the light and heat has come from, and how far the energy has travelled before reaching you.

KAWSER: It's going to be a sunny day, well, for some of us. And if we take a look at the weather map, we can see where it's going to be sunny where we don't have any cloud and it's clear. Now the amount of sunshine that we get can affect our daily lives in lots of ways. And that's why it's very important to find out how much sunshine there is. So how do we measure sunshine hours? And why is it useful?

Farmers need to know if the crops are getting enough sunshine and if there's too much sun they'll need to water the crops more or pick fruit to stop the sun drying it out. We need to be aware of how much time we spend in the sun and apply sun cream to protect our skin from damage.

Sunshine is measured at weather stations all around the UK. Let's see how it's measured at the MET Office in Edinburgh.

PUPIL: Can you tell us how sunshine hours are recorded?

MET OFFICE WORKER: Yeah, we measure sunshine using a sunshine recorder like this. It works on the same principle as when you have a magnifying glass and you focus it on a piece of paper which then burst into flames. In this case, this sphere is your magnifying glass and the card underneath is your paper. And as the sun moves round, this focuses on a different part of the card as it goes round and you end up at the end of the day with a card that looks a bit like that. You add up the length of all the burnt through bits. Then, with each of those white lines being an hour apart, you can then work out exactly how much sunshine you've had during the day.

KAWSER: The Campbell Stokes sunshine recorder was invented by John Francis Campbell in 1853 and it was updated by Sir George Gabriel Stokes in 1879. In the past, this was the way all sunshine hours were recorded.

PUPIL: How do we record sunshine hours nowadays?

MET OFFICE WORKER: Nowadays, we use this instrument: a sunshine duration detector. It's measuring the strength of the sun as it hits it. And whenever the strength of the sun is one hundred and twenty watts per square metre, it will interpret that as being sunshine, it'll give you a total for every hour of the day and total for the full day.

KAWSER: You don't need special equipment to measure sunshine hours. You can do it by observation. Count sunshine hours where you are by making a chart from sunrise to sunset and marking when the sun is in the sky. But be careful when looking up to the sky that you don't look into the sun.

PUPIL: Hey Mia, how much sunshine did we have today?

PUPIL: At 11am, we had sunshine then at twelve noon, we had cloud with a little bit of sunshine and at 1pm we had sun and at 2pm we had clouds again.

KAWSER: So now you know how to measure sunshine hours, maybe you can measure how much sunshine you get where you are.