Earth and the Solar System: Presentation script

A walk through the Universe

Outline script
Start by asking the children something along the lines of, "What do you know about space?" This will give you some idea of what their current level of knowledge is, and with a bit of luck will produce some answers such as "space is very big" that you can use to lead into the talk.

Children will ask good questions so be prepared. They like to learn the names of the Moons of the outer planets.

This script is organised by slide number on the corresponding PowerPoint presentation. “Stage directions” are in []. Remember to treat this as a guide: adjust according to the response you get from the children.

Slide 1: Space is Big
[I normally set the presentation up so that this slide is showing while the children come in and settle down. The teachers generally recognise the quote – maybe some of the kids will too!]

Today I’m going to talk about space. What do you know about space?

[Cue forest of little hands! Don’t just settle for one answer – pick quite a few kids, of a range of ages if you’re dealing with a mixed class, and use the answers to “advertise” bits of the talk. Sample answers, with suggested responses:

  • There’s no air there. (Indeed there isn’t – that’s why it’s so hard for us to explore.)
  • That’s where planets/stars are. (That’s right: we’re going to talk about that later.)
  • Rockets go there. (Yes they do: we’ll see some pictures taken from spacecraft later.)
  • There’s no gravity there. Oh yes there is: why do you think the Moon keeps going round the Earth, and the Earth round the Sun? If there weren’t any gravity we would go one way and the Sun would go another, and it would get awfully cold and dark round here!1
  • It’s really big/It goes on for miles and miles. (Yes, and what I’m going to try to do here is show you just how big space really is.)

Slide 2: You Are Here
We’re going to talk about space, but let’s start with something smaller. Do you know where this is?

[Most classes will contain at least one child who realises or guesses that it’s their school.]

That’s right. This [point to school building] is your school as seen from a low-flying plane or a balloon, and this [bottom left] is from a high-flying plane. [Click to get right-hand picture.] And this is what your school looks like from an orbiting satellite – we’re about here. We’re pretty small, aren’t we?

Slide 3: The Earth
Britain looked pretty big on the last picture, but compared to the whole of the Earth it’s quite small. [Point to Britain: it’s half-hidden under cloud. Joke about the weather!] Africa is much larger, isn’t it?

Slides 4 and 5: The Inner Planets – (names are on slide 5)
There are pictures of three more planets here besides the Earth. They’re all drawn to scale, so the Earth is the biggest one shown here. Can anyone name any of the others?

[Many primary school children know some planet names, but they seldom know which is which! Keep trying then show slide 4: the answers are Mercury, top left; Venus, top right (an unusual view, because it’s a Magellan radar image in false colour, not the featureless white cloud tops you get in the optical); Mars, bottom right.]

These are the four planets closest to the Sun: Mercury, Venus, Earth, and Mars, and Earth is the biggest. But is Earth the biggest planet in the whole solar system?

[Ask for a show of hands: who thinks it is? Who thinks it isn’t?]

Slide 6 and 7: The Outer Planets- (names are on slide 7)
Well, here are the other planets of the solar system, and here’s Earth [point to it – it’s in front of Jupiter]. So you see it’s not the biggest, by a long way. Does anyone know the names of these planets? [Work your way through. Then show slide 7: the answers are Jupiter, top left; Saturn, with rings; Uranus, top centre; Neptune, top right. Pluto is below Neptune and is no longer classified as a planet. The extra little dot is Pluto’s moon Charon.]

[When someone gets Uranus:] Yes, that’s Uranus. But did you know it was nearly called George? It was discovered by William Herschel back in 1783; he was a musician and amateur astronomer working at the English court, and he wanted to call it George. Why do you think that was? [They’ll guess that it was his name – point out that his name was William – or his middle name, or his son’s name. Ask who he might have wanted to impress. If that doesn’t work, say that if he’d discovered it today, he would have wanted to call it Elizabeth. That usually does the trick.] Yes, he wanted to call it after King George III, because he thought it might be good for his career. But the other astronomers thought “Mercury, Venus, Earth, Mars, Jupiter, Saturn, George” sounded silly, so it was renamed Uranus, because in the Greek myths Uranus was Saturn’s father just as Saturn was Jupiter’s father.

[When someone gets Neptune:] Yes, that’s Neptune. It’s easy to remember which is Uranus and which is Neptune, because Neptune was the Greek god of the sea, and Neptune the planet is blue like the sea. But that was just luck, because nobody knew it was blue when they named it: it just looked like a little dot of light in the telescope. This picture was taken by a spacecraft called Voyager that visited all the outer planets.

[When we get to Pluto:] It’s very tiny, isn’t it? It’s even smaller than the Moon. Many astronomers think it shouldn’t be called a planet at all – so the solar system really has only eight proper planets, even though all the books say nine!

[When all the planets have been named:] So now we know what all the planets look like and how big they are. Jupiter is the biggest. Is Jupiter the biggest thing in the whole solar system? [Ask for a vote. Agree that the answer is “no”.] What is the biggest thing in the solar system?

Slide 8: The Sun
Yes, the Sun. Here’s a picture of the Sun and Jupiter – see how much larger the Sun is. In fact the Sun weighs 1000 times as much as Jupiter, and Jupiter weighs more than 300 times as much as the Earth.

Now I know these numbers are quite hard to get your heads round, so I’ve got a small demonstration. First I need two volunteers. [Pick two and get them to hold either side of the Sun model (see Apparatus List). Now who wants to be Jupiter? [Similar forest. Get the lucky winner to hold the cardboard Jupiter up in front of the Sun, as in the slide.] And who’s going to be the Earth? I warn you it’s not very impressive being the Earth! [This won’t put them off. Try to get your selected child to hold just the side of the mount, so the audience stand a chance of seeing the Earth disc.] Now let’s be really unimpressive – who wants to be Pluto? [Same comment!]

[Get your volunteers to stand there for a while so the audience has a chance to take it in. This is a photo-opportunity: teachers often want to take pictures.] OK, that was great, thank you. Can I have my planets back please?

Slide 9: The Solar System
So now we see that the Sun is by far the biggest and most important thing in the solar system. That’s why, when we look at other stars, we only see the star and not the planets orbiting round it. But now I want you to think about how far away those planets are. Here’s a diagram of where the planets are, but it’s not very good because they are not drawn to scale – the person who drew the picture wants you to be able to see them! So I’ve got another demonstration. (see Apparatus List). Imagine we shrink the Sun down to 2 mm across – that’s about the size of Pluto that you were holding up a moment ago [point to Pluto volunteer]. This is how far Mercury is from the Sun if the Sun is 2 mm across [hold up Mercury ribbon]. And this is how far away the Earth is [hold up Earth ribbon], and this is Mars [hold up Mars ribbon]. I think it must be pretty cold on Mars, don’t you? But it’s even colder on Jupiter [stretch Jupiter string out at about shoulder height].

The other planets are even further away, so I’m going to need some help here. Who wants to be Saturn? [Pick volunteer, and ask him or her to take one end of the Saturn string and unreel it.] This is how far away Saturn is – remember the Sun is only 2 mm across in this map! [Repeat with Uranus – “or George” – and Pluto.] Pluto is so far from the Sun that it takes over 4 hours for the light to reach it. It only takes 8 minutes for the light to reach the Sun. [Thank volunteers and dismiss them.]

So now we know how big the solar system is. But the Sun is only one of a hundred thousand million stars in our Galaxy. On this scale, with the Sun 2 mm across, how far do you think it is to the nearest star? [You will get wild guesses, especially from younger children. Try using “bigger” and (if necessary) “smaller” to extract a reasonable number. If nothing sensible emerges after a dozen or so guesses, give up.] About 59 km away – that’s somewhere in Leeds(or whatever town is appropriate for your venue). It takes light four years to reach the nearest star: you had just started school when the light we’re seeing from that star left.

Slide 10 and 11: The Milky Way
This [top] is a picture of our Galaxy. It’s hard to see what shape it is, because we’re inside it, but if we could take the starship Enterprise and look at it from outside it would look like this.

Slide 11
Our Sun is about here [yellow Sun symbol]. How many years do you think it takes the light from the centre of our Galaxy to reach us? [Wild guesses. Offer the teachers a chance.] About 25000. We were cavemen when that light started on its way.

[Click to show distances]

Slide 12: Distances – an opportunity to revise before moving on
[Ask questions and use the slide to give the answers by clicking the wording on.]

It takes 8 minutes for light to reach us from the Sun.

(You could add that it takes about 1 second for light to reach us from the Moon.)

A light-year is the distance travelled by light in 1 year.

The Sun is our nearest star.

Our next nearest star, Alpha Centauri is 4 light years away.

The Milky Way is 100 000 light years across.

Slide 13: The Local Group
The nearest big galaxy to ours – in fact it’s a bit bigger than ours – is called the Andromeda Galaxy.

Slide 14
The light from this galaxy has taken two million years to reach us – humans like us weren’t even around then. [Click to show galaxy] You can actually see this galaxy, in the constellation Andromeda, if you find a place where you have very clear skies and no street lights. It’s the most distant thing you can see without a telescope.

Slide15 and 16: The Local Supercluster
If we take a big telescope and look a little further, we can see lots of galaxies. Every dot on this map is a galaxy like ours. The big clump of dots on the right is called the Virgo cluster, and it’s about 65 million light years away.

Slide 16
So the light that made this picture started out 65 million years ago. What else was happening then? [Children being children, someone will probably know it’s the time at which the dinosaurs became extinct!- Click for wording to appear.]

Slide 17: The Universe is mind-bogglingly big!
We have been talking about light years. Let’s try to think about distances again.

The Sun is 150 000 000 km away.

When we look at the night sky the bright stars are about one million times further away than the Sun! We need to imagine the distance to the Sun then lay a million of them end to end - that's had to imagine.

If we can see any galaxies they will be about a hundred thousand times further away than the bright stars! This about 15 million, million, million km away! Image the distance to a bright and lay 100 000 end to end!! Totally mind-boggling! [Emphasise that this is not 3x15 million]

Slide 17: The Hubble Ultra-Deep Field
Using the Hubble Space Telescope, we can look even further away than with the most powerful telescopes on earth. Almost everything in this picture is a galaxy [if you want, you can point out that the things with diffraction spikes are stars, and count them – there are 2 seen clearly and one in the upper left corner below the dark orange galaxy. The diffraction spikes cannot be seen usually when projected.]. Some of these galaxies are over 10 billion light years away. The universe was very young when this light started out: in fact, if you take the present-day universe to be about as old as I am, we are seeing those galaxies as they were when the universe was as old as the youngest people here. [I’m 46, and I’m taking the line that the most distant visible galaxies are seen as they were when the universe was about 10% of its present age.]

The solar system hadn’t even been born when much of the light that made this photograph started its journey.

And at this point, having gone from the roof of your school to the most distant objects ever photographed, I’ll stop talking and ask if you have any more questions.

With thanks to Susan Cartwright, University of Sheffield

1 They get this one from seeing “weightless” astronauts in orbit. It’s quite hard to fix. You can try the “Newton’s cannon” argument, using a ball to represent the Earth and your hand to show trajectories for faster and faster cannonballs.

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