A collection of down-to-Earth facts about our planet and its place in the solar system.
This collection introduces the Sun as the main source of light and heat on Earth. It explains that the Earth orbits the sun and rotates as it does so, causing the day and night cycle. As well as rotating, the Earth has a tilt in its axis that brings the northern and southern hemispheres closer to and further away from the Sun each year, which causes the seasons.
The Moon's reflection of light from the Sun is explained, as is its change in appearance each month between a new moon and a full moon.
The effect of a planet's mass on an object or person's weight is explored and pupils can explore the idea of being heavier on Jupiter than on Earth, but lighter on Pluto. The consequences of weightlessness on the human body are illustrated by British astronaut Helen Sharman aboard the International Space Station.
These clips are from the BBC series, Primary Focus Science and Science Clips, Earth, Sun and Moon.
Sun, shadows and time of day
Our main source of natural light is the Sun.
Nuclear reactions at the core of the Sun create energy in the form of heat and light.
Although the Sun is some one hundred and forty four million kilometres away.
It takes just eight minutes for its light to reach us on Earth.
The Earth as we know it, could not exist without the Sun's light, every living thing on this planet needs light, to grow and survive.
Although the Sun appears to move through the sky.
It is really the Earth and you that are moving around the Sun, the Sun appears to rise and fall as the Earth turns you around to face it.
Whenever the Sun shines brightly you can see the strong shadows it casts.
At noon when the Sun is high, shadows are short, but as it sinks lower in the afternoon, the shadows grow longer and longer.
Night falls when the Earth spins around so far that we face away from the Sun.
Earth's orbit of the Sun
If you imagine a line running between the North and South Poles, the Earth rotates about this line, called an axis.
In winter, the North Pole is tilted away from the Sun.
So the Sun's rays can't reach places in the far north, the Arctic Circle.
In these places, it stays dark all day in the middle of winter.
But the Earth travels around the Sun, taking a year to do so.
As the Earth moves around the Sun, in the north, you can see the amount of daylight gradually increasing, so the days there get longer, as in springtime.
By June, the Earth has moved around the Sun, so the North Pole is now tilted towards the Sun and places in the far north get really long days.
At the North Pole, it doesn't get dark.
The Earth takes a whole year to orbit the Sun.
But it's the tilt which gives us the seasons.
Here, the North Pole is back in midwinter darkness again.
How do we know the Earth is spherical?
We know the Earth is round, like a ball.
But only 50 years ago, such pictures weren't possible.
Two and a half thousand years ago, it was impossible to see beyond your immediate neighbourhood.
And if this was what you saw, what would you think?
It looks flat. It feels flat.
Most people just assumed the Earth was flat.
But in Ancient Greece, some people were asking questions, including the philosopher Aristotle.
He reasoned that the world was a sphere.
And he also had evidence.
What was this evidence?
At first sight, ships appear to just get smaller and smaller as they disappear into a hazy horizon.
But in the clearer Greek skies, Aristotle observed that the hull, the bottom, disappeared first.
He maintained that would only happen on a curved surface.
If the Earth was flat, we'd see the whole ship getting smaller and smaller until it becomes a tiny dot.
But on a curved Earth, when the ship reaches the horizon, the hull disappears first.
And there was further evidence in the night sky.
By this time people had discovered you saw different constellations as you moved north to south.
Again, Aristotle argued, that proved the Earth was round.
If you were standing on a flat Earth, looking at the night sky, then surely you'd see the same stars, on the same night,wherever you stood?
But not if the world is round.
And finally, he observed a shadow cast by the Earth on the Moon as it was eclipsed - it was curved, not straight.
How to tell the time of day from shadows cast by the Sun. The Sun is the main source of light on Earth. Nuclear reactions at the core of the Sun create energy in the form of heat and light. The light reaches the Earth in just eight minutes and life depends upon it to grow and survive.
An explanation of how seasons and day length are affected by the Earth's tilt. The Earth is not completely upright - it leans at a slight angle, so that the northern and southern hemispheres are sometimes tilted towards the Sun, sometimes away. This creates warmer and colder periods called seasons.
How people discovered the Earth is round or spherical. Aristotle's reasoning is explained. The evidence includes a ship's hull disappearing first over the horizon.
The Moon and its orbit around Earth
I'm going to be the Earth, and this is the Moon.
The Moon in the sky is lit up by the Sun.
The Moon reflects the Sun's light, but the light can't go round corners, so only half of the Moon is lit up by the Sun.
The other half of the Moon is dark.
The Moon orbits the Earth.
As it does that, the lit-up side stays facing the Sun.
Let's look at it on its journey.
This part of its journey, me living on the Earth, I can't see any of the lit-up side.
So I can't see the Moon in the sky at all. It's what we call a new moon.
As the Moon starts to make its orbit, I can suddenly see a tiny sliver of the lit-up side, so we call it a crescent moon.
I can gradually see a little bit more.
That's what we call a quarter moon.
A little bit more… and that's going to carry on until the Moon is in this position.
Opposite the Sun, I can see all of the lit-up side. It's a full moon.
It's going to carry on around the Earth, and I can start to see less of the lit-up side and you can see a quarter moon again.
We see a crescent moon again… and once again, I can't see any of the lit-up side - it's a new moon again.
Gravity on Earth, Jupiter and Pluto
The Earth pulls Femi's mass of 55kg with the force of about 550 newtons.
But if she were able to visit Jupiter, her mass would be just the same as on Earth - 55kg.
Wherever she is, in space, on Earth, or even on Jupiter, she's still made of the same amount of stuff.
But on Jupiter, she would feel much heavier.
The Earth and Jupiter are planets that are very different in size.
Gravity is the pull that the planet exerts towards its centre and gravity depends on mass.
Jupiter has more mass than Earth, so on Jupiter her weight would be nearly 1,400 newtons, because the force of gravity is greater.
The force of gravity on Jupiter is two and a half times gravity on Earth.
So, imagining that Femi could take herself off to Pluto, which is even smaller than our Moon, the force of gravity would be much weaker than on Earth.
Though her mass would be the same, her weight would only be about 20 newtons.
Weightlessness in space
Helen Sharman is a British astronaut.
When I was weightless, there was no force left to tell me up from down.
So the roof of the space station doesn't really have to look any different from the floor.
My sleeping bag was tied to the wall.
It means you can use everything, all three dimensions of the room.
It was very easy for me to move from one side of the space station to the other.
All I had to do was push off from one wall and I would float to the other end.
The biggest problem we had was that things would float off if you didn't tie them down properly.
So if you go looking for something, you don't just look downwards, you have to look all around.
The funny thing was, of course, the food didn't sit down at the bottom of my stomach.
You can feel it sloshing about, floating around inside.
The Moon is not a source of light. The Moon is only visible from Earth when light from the Sun falls on it and is reflected back to Earth. At times the Earth casts a shadow that seems to change the Moon's shape.
If a person with a mass of 55kg were to travel to Jupiter or Pluto, the effects of gravity would be very different from those on Earth. Gravity is the pull that a planet exerts towards its centre.
In a space station, you can no longer feel the effects of the gravitational pull from the Earth. Where there is no gravitational force, you cannot tell up from down.
Teacher Notes
These clips can introduce pupils to the Sun and how it casts shadows upon the Earth. In pairs, the pupils could use chalk to draw around each other's shadows on the school playground. Standing in the same spot, they could draw around the shadows at regular intervals. They could take photographs and discuss what happened to the shadows and why.
The class could discuss the effects on the seasons of the Earth's tilt and orbit of the Sun. Teachers could demonstrate this phenomenon further by using a torch and an inflatable globe or ball. This same technique can be used to explain the way in which the Moon appears to change shape as it orbits Earth.
Explain the constant force of gravity and how it differs from one planet to another. In more advanced sessions it could be used to illustrate the difference between mass and weight. The pupils could be asked to observe how objects stretch elastic bands and springs, leading to work measuring mass in newtons.
Curriculum Notes
These short clips are relevant for teaching Science at KS2 in England, Wales and Northern Ireland and second level in Scotland.
