If You Could See The Earth... (1967)

[Music] [Applause] [Music] [Applause] [Music] [Applause] [Music] for millions of years man has lived on the earth and has had some very strange ideas about it because it looked flat he decided that it was flat definitely [Music] flat in India centuries ago some people thought that the Earth rested on the backs of huge eles the elephant stood on a giant turtle which swam forever in an Endless [Music] Sea there were ancient Greeks who believed that the Flat Earth was surrounded by an ocean with towering pillars supporting the sky with the Sun the and all of the [Music] stars there were those who insisted that the Earth had an edge Beyond which lived frightful demons if you came too close to the [Music] edge as time went on however people became dissatisfied with these ideas of what the Earth was like it could be flat they reasoned because it looked flat and felt flat but why did the sun always set in one place in the evening and Rise the next morning in [Music] another why did ships disappear below the Horizon as they sailed out to [Music] seea if the Earth were not flat and if a ship sailed always in the same direction it might eventually return to where it had started when a ship did indeed sail around the earth man could no longer doubt its shape it was round today if you were an astronaut you could fly far out into space and see what the Earth is really like one fire [Music] Zero from here you can see that the Earth is a sphere that seems to hang in space if you take a closer look you can see that it is partly covered with water or oceans and partly with land which we know as continents notice that there is about twice as much water as there is land that each continent has mountains valleys deserts lakes and rivers each a different size and shape the Earth turns constantly this is called [Applause] [Music] rotation rotation how do it work find something that's round the orange will do anything shaped like this we call a sphere next we need a [Music] stick now push the pencil through the middle of the [Music] orange the orange turns or rotates around the pencil the pencil can be called an axis the axis around which the orange [Music] turns now let's look at the Earth it turns just like the orange but the Earth doesn't have an axis the Earth's axis isn't something that you can see or touch like the pencil but it does have one if you could see it it might look like this with the North Pole at one end and the South Pole at the other although we can't see the axis the Earth still turns or rotates around it now let's go farther out into space where we can see both the Earth and the Sun [Music] outside the capsule you will simply float because in space things don't fall down as they do on Earth from here we can see that the sun's Rays shine on the earth giving heat and light but does the sun shine on all of the Earth at [Music] once on the side that's facing the Sun sun it's daytime on the Earth but what about the side that's facing away from the Sun what's happening there yes people are asleep because it's night time on the dark side of the earth what does the rotation of the earth have to do with night and [Music] day the Earth's rotation causes day to change into night and night into day again let's see a day is 24 hours long so that must mean it takes a day for the earth to make one rotation we've learned something about the Earth here in space but there's more to learn back on Earth itself [Music] [Applause] can we find out for instance why things always fall to the Earth they don't in space why is it that unless something is held up it always falls down is there some kind of force which pulls us and everything else to the Earth there is and the force is called gravity [Music] pick an apple let go of it what pulled it down what pulls them all to the Earth gravity if it weren't for Gravity our Earth might be a rather difficult place in which to live everything would float like an astronaut in space gravity Keeps Us and everything around us on the ground and holds us there we've learned a lot about the Earth but we've only begun to learn more we can use a model of the Earth a globe like the Earth the globe is a sphere it surface is divided into oceans and continents and it rotates on an imaginary exis just as the Earth itself wherever the Sun Shines on the earth it's daytime and wherever it doesn't it's night rotation causes day to change into night and night back into day again gravity causes things to fall to the Earth and holds them there actually the glob probe can help with many questions about the [Music] Earth why do we have winter and summer why do the seasons change why is it colder at the North Pole than at the equator why do snow and ice never melt at the North and South polls why do we have temperate zones in Equatorial regions [Applause]