Hello and welcome to today's lesson from the Unit, Earth, Sun, and Moon.

This lesson is called "The Shape of the Earth".

Hi, I'm Mrs. Waller and in this lesson today, you're able to consider evidence from the past and describe the shape of the earth.

Let's start by taking a look at the keywords we'll be using in the lesson today.

Earth evidence, spherical, globe, horizon.

Just take a moment.

Have you heard of some of these words before? Do you know what any of these words mean already? Well, don't worry if not because we'll be using these words through the lesson today.

Today's lesson is in two parts.

The first part, we'll be looking at early ideas about the earth and then moving on to look for more evidence for his spherical earth.

Today we're going to be looking at lots of evidence from the past.

We know that throughout history, people have disagreed about the shape of the earth.

There have been some ideas that have included things like, the world is a spinning disc in the ocean or how about, the earth is flat with a dome for the sky, or finally, well maps are flat, so the earth must be flat.

Do you agree with any of these ideas? Today we are particularly thinking about the earth.

Now we know that for centuries, people have looked up into space, they've examined the night sky and they've wondered about the shape of stars and planets and in particular, the shape of the planet where we live, planet earth.

So take a moment to think about what shape do you think planet earth is? Maybe you could share your ideas with someone else.

So hopefully you've got some ideas now about what shape you think the earth is.

But for many years, people thought the earth was flat.

Scientists have gathered information called evidence, to prove that this is not true.

Now that word there evidence, that's one of our key words in the lesson today.

So we're looking at information that scientists gather together to make a case for something being true or not true.

Around 2000 years ago, so we're talking a long time ago, a very famous Greek scientist called Aristotle made some very important observations and what he noticed about the night sky was so important that there are now statues of him to celebrate his discoveries.

What Aristotle observed was that when a ship sails out to sea, it looks like it's very gradually disappearing at the horizon line.

So there's a photograph of two large sailing ships and I've put a label on the horizon line.

That's another one of our keywords from today's lesson.

The horizon is the line in the far distance where the sky appears to meet the land or to meet the sea.

So it looks like there's this straight, horizontal line here where the sky appears to meet the sea and when ships are sailing away from us, it looks like they gradually disappear.

The bottom of the ship disappears from view first and then the last thing that we see is the very top of the ship.

So we don't see the whole ship disappearing all at once at the same time.

Now Aristotle is really curious about this and this led him to think that this potentially could be evidence that the earth is round and not flat.

So I'm going to tell you a little bit more about Aristotle's evidence, but first I'm just going to ask you a few questions to check your understanding of the first part of this lesson today.

Scientists collect evidence about the shape of the earth.

What does evidence mean? Information to show something is true.

Information to show something is not true or both of these are correct.

Take a moment to think about which one will you choose.

Yes, that's right.

It's actually both of these are correct.

So the evidence that scientists collect is information that helps us to decide if something is true or not true, well done.

Now we know that people have disagreed about the shape of the earth for centuries.

What word describes the actual shape of the earth? Is the earth flat, is the earth bumpy, is the earth round? So don't forget, we're looking for the word that describes the shape of the earth.

And the correct answer is round.

And we know that Aristotle's evidence that he'd collected whilst observing ships disappear and appear at the horizon really did go some way in helping us to believe that that's the true representation of the earth.

Moving on to your first practise task now.

Some children are discussing their ideas and evidence about the shape of the earth and we've got some different ideas here.

Laura says, "If you keep sailing in the same direction, you will come back to the same place you started from." Jun says, "The top of a boat appears first when it is sailing towards you." And Sofia says, "Under the waves of the sea the surface of the earth is completely flat." So you might want to pause the video and think about these ideas a little bit more and I'd like you to decide Laura, Jun, Sofia, who supports the idea that the earth is round and whose idea is incorrect and can you explain why? Remember to think like a scientist.

So let's take a look at these ideas again.

Who supports the idea that the earth is round? Well, Laura and Jun are both discussing evidence that the earth is round.

They are both correct.

So Laura says, "If you're in a ship and you keep sailing in the same direction, you will eventually come back to the same place that you started from." That is correct, yes.

And that's more evidence to suggest that the earth is round.

Now remember what Jun said, "It's the top of the boat that appears first when it is sailing towards you." So that's in line with Aristotle's ideas that when a boat is sailing away from you, it's the bottom of the boat that disappears first and the top that disappears last.

So in reverse of that, if the ship is sailing towards you then you're going to see the top of the boat first and the bottom of the boat will be the last thing that you see as it travels over the curved rounded surface of the earth.

Well done everybody, some tricky questions here.

So moving on to whose idea is incorrect and can you explain why? So that leads us to the remaining idea that Sofia's idea must be incorrect.

And she says that under the waves of the sea, the surface of the earth is completely flat.

Now I wonder if you agreed with Sofia.

Now we know that that is an incorrect idea because the surface of the sea looks completely flat.

However, it's curved because the surface of the sea sits on the surface of the earth and we know that the earth is shaped round like a ball.

Well done.

We're moving on to this second part of this lesson today now, and we've already started thinking about early ideas and some evidence from the past.

So in the second part today we're continuing to look at the evidence that's been collected for a spherical earth.

Let's go back to Aristotle's evidence.

So remember he showed that as a ship travels over the earth's curved surface, the bottom of a ship disappears from view first and the tallest part disappears last.

So I've put together a scientific diagram and if you can see the little person standing at the curve of the earth and we've got the dotted line which shows the view that the person can see representing the line of the horizon.

And at the moment, we've got this sailing ship and we can see all of the ship.

Now as the ship sails away from us, we are noticing that the bottom of the ship appears to disappear first.

And as the ship continues to sail away, we can only see the very top part, which are the sails of the ship, before the ship appears to completely disappear from view.

Does that help you to understand that a little bit more? So let's just compare that idea to which part of a ship would you see if the earth was flat, it would be a different view.

So think about if the earth was flat and which part of the ship would you see as it was sailing away from you? So have another diagram here to help you to understand what you would actually see.

If the earth was flat, you would see the entire ship as it sailed away from you.

So we can see the entire ship now, we've got our representation of a flat earth and the ship is sailing away and we can still see all of it and it's sailing away a little bit further and we can still see all of it.

And we know that that's not actually true.

That's not what you would observe in real life.

If you've ever stood at the beach, at the shore, and you've watched boats sailing away and towards you, we know that this evidence is not true.

It's evidence like this that has helped us to know and understand about the real shape of the earth.

Let's hear about some more evidence from the past.

So we're still going way back into history to 1519 and we know that a navigator from Portugal called, Ferdinand Magellan, started sailing from Spain with a group of other sailors.

Now this was a really brave thing to do at the time because many or most people at the time thought that the earth was flat and they were worried that the further these sailors sailed away, they would get to the edge of the flat earth and they would fall off.

So they kept travelling in the same direction and three years later, the ships came back to the same place they had started from.

This was the very first time, it was the first expedition that anybody had ever sailed around the world.

So you can see here by the diagram that the ship, it didn't fall off the flat earth, it kept sailing and sailing and sailing.

And in three years time, it was a long expedition, it finally came back to where it started from, more evidence to prove that the earth is round and not indeed flat.

Let's think about what people think of the shape of the earth today.

Now it's due to evidence collected from the past from incredible people like Aristotle and Magellan, that most people today do agree that the earth is round like a ball and we call this shape a sphere.

Now you've probably heard the word sphere before, maybe in your maths lesson when representing the 2D shape of a circle in a 3D form.

Knowing that the earth is the shape of a sphere, we can use a globe as a way of representing the entire shape of the earth.

A globe helps us to see that we live on the surface of a spherical planet.

All the countries of the world can be found on a globe.

And now I'm going to do a few checks for understanding for the second part of today's lesson.

Why is a globe the shape of a sphere? A globe is a shape of a sphere, so you can bounce it.

A globe is a shape of a sphere because the earth is a sphere.

A globe is a sphere, so it has no sharp corners.

Which one do you think? Yes, that's right.

Remember, a globe is a representation of the earth and the earth is the shape of a sphere.

Therefore the same for a globe.

Now we have three images here.

Which image below do you think is the correct way to represent how we live on the earth? And can you also think about why do you think this? So we've got representation A and B and C.

Take a moment to think about which one do you think is the correct way to represent how we live on planet earth? And the correct answer is B.

Now this is a tricky one.

Remember, throughout history people have disagreed about the shape of the earth and we actually live on the surface of the earth and remember that the earth is the shape of the sphere.

Moving on for your practise tasks now.

Now I can show you lots of pictures, lots of photographs, lots of diagrams of ships disappearing over a spherical earth at the horizon line.

But I think it would be brilliant if you could make a model to represent this and have a look for yourself.

So our first practise task, I would like you, if you've got a toy ship or a toy boat, but don't worry if you haven't, you could find a small box and maybe stick something in there and make a little mast with a triangle piece of card.

And first of all, we're thinking about if the earth was flat.

So to represent that we're going to use a long, flat surface such as a table and this is going to be our flat earth.

So what you need to do is you need to get down to the level of the horizon line.

So you might want to bend down or kneel down on the floor so that your eyes are level with the table.

Just like in this diagram here.

Now what I need you to do is to get somebody to help you and they're going to very slowly move the boat or move the toy ship away from you.

And I want you to think about what do you observe? So imagine that you are Aristotle way back 2000 years ago making your observations and collecting your scientific evidence and what do you observe as the ship is first of all moved away from you? And then as the ship is moved towards you, and I want you to think about this as collecting your scientific evidence.

What evidence is this for the shape of the earth? Pause the video and have a go.

So here's what you should have observed as the ship was moved away and towards you on a flat table representing if the earth was flat.

As the toy ship moves away on the flat earth, I can see every part of the whole ship all of the time.

Is that what you observe too? So what evidence is this for the shape of the earth? Well, this is not what happens in real life because the earth is not flat.

So can you remember that the evidence that we collect goes towards saying that something is true or also that something is not true.

So this evidence helps us to understand that the earth is not flat.

Let's go back to our model now.

So this time we need to think about how we can represent a sphere for the earth.

So I'm going to use this large ball.

You could use something if you've got a football or a beach ball or something like that that you can use.

You're definitely going to need somebody to help you here to hold the ball in place and maybe yes, to even hold the ship in place on top of the ball.

Now you're going to stand up this time or maybe sit on a chair depending on the size of the ball.

And your partner is going to hold the ship on top of the ball and this is going to represent a spherical earth.

So you can see here on the diagram that again, your eyes are level with the top of the ball so you should be looking around the bottom of the ship.

And what we're going to do this time is ask your partner to very, very slowly move the ship away from you but moving it on the surface of the ball.

And then I would like your partner to slowly move the ship towards you, but all the time remember, they're not floating it away in a straight line.

They're following the ball's curve.

Collect your scientific evidence this time, make your observations and I want you to be able to explain what evidence is this for the real shape of the earth.

You might want to pause the video now and have a go.

So by now you'll have had time to try out your model.

And what did you observe as the ship is slowly moved away and towards you, but this time following the ball's curve? Well, if I start with the ship on the other side of the ball and it moves very, very slowly towards me, I can see the tall mast first.

So is that what you saw? If you've made a boat, did you see your cardboard triangular sail appearing first before the rest of the ship? So you should have seen the tall mast first before any other part.

So what evidence is this for the shape of the earth? This is what happens when real ships appear at the horizon line.

We see the tallest parts first as they appear over the curved surface of the earth.

Well done scientists, you've collected your own scientific evidence today and you've been able to explain the shape of the earth.

Well done everyone.

We've come to the end of today's lesson and it's time to summarise our learning today.

We know that there have been disagreements for many years about the shape of objects in space.

Take a minute to think about what some of those disagreements might have been and some of the ideas that people have had throughout history about the shape of the earth.

What else have we been learning today? Yes, we know that there is evidence from the past and this has helped us to understand the shape of the earth.

And if we go back to thinking about Aristotle's ideas, he was particularly observing ships as they appeared and disappeared at the horizon line.

Anything else? We know that the earth is round like a ball and we call this shape a sphere.

The shape of the earth can be represented using a globe.

Now would be a great time to go back to those keywords from the start of the lesson and explain to somebody else what each one of those words mean.

Well done, you've come to the end of today's lesson and now it's time for you to have a go at the exit quiz.

Remember to think like a scientist, and I look forward to seeing you for the next lesson next time.