# Lesson video

In progress...

Hello there, my friends, and welcome to this lesson on the unit of Building Locational Knowledge: Hemisphere and Tropics.

My name is Mr. Pedroza and in this lesson, we're going to have a look at the following question.

So the question is, why is there a time difference between different countries? I always wondered that, so I'm glad that I'm doing this lesson with you.

Now, let's look at the structure of the lesson.

We'll begin with the star words, and then after that we'll have a look at, what is a time zone? Then we're going to look at what is a Meridian, and why is it important? We'll look at why is there a time difference between countries, and then what is a date line? We'll have a look at, how does time difference affect human activity? And then we'll do our end of lesson quiz.

Things you're going to need in this lesson are going to be, exercise book or paper, you need a pencil or pen, and then you're also going to need a ruler.

So if you haven't got those things, go and get them now.

Great job my friends, that was super speedy.

Now, let's look at the star words, we've got five, we got time zone, meridian, Prime Meridian, and date line and axis.

A time zone is a region, in which all the clocks are set to the same time.

A meridian is an imaginary line around the Earth that passes through the North and South Pole.

And Prime Meridian is a meridian that passes through Greenwich in England.

And it's used as the starting line for the measurement of longitude East and West.

A date line is an imaginary North to South line drawn in the Pacific Ocean.

And an axis is a real or imaginary line through the centre of an object, around which the object turns.

So let's begin with, what is a time zone? Now, a time is an region or area that observes the same standard time.

Time zones are divided by imaginary lines called meridians, which run from the North Pole to the South Pole.

And the world is divided longitudinally into time zones.

Remember that lines in longitude, helps to find out how fast east or west a place is.

And these lines from top of the Earth to the bottom, cause they run North to South, they run vertically.

Now on this map that you're seeing right now, the colours, they represent different time zones.

A common misconception is that there are only 24 time zones, because there are 24 hours in a day, however, due to some countries having half-hour time zones, there are currently more than 24 time zones in the world.

What I want you to do is really, really simple.

Mark the North and South Pole, and then as a challenge, there's a question so, what are the imaginary lines that run from the North to South Pole called? They are called, what are they called? Again, you can point to the North and South Pole.

If you have access to a printer, you can print them out, and then you can complete that task.

So at this point, pause the video and complete this task.

Okay, let's see, where is the North Pole and the South Pole? The North Pole is of course, in the Northern Hemisphere.

The South Pole is in the Southern Hemisphere.

And then my challenge is, what are the imaginary lines that run from the North to the South Pole called? They're called meridians.

Excellent job my friends, well done.

I'm going to leave it up, for you to check your work.

Okay, let's have a look at the next one.

So what is a meridian and why it's important? So as a reminder, time zones are divided by imaginary lines called meridians, and they run from the North Pole to the South Pole.

Now notice that there's a red line running through the United Kingdom.

So there's this red line, and it runs through the United Kingdom.

Why do you think that may be? Well, why is this significant? Well, this red line indicates the Prime Meridian.

And so let's find out where this red line is located, and why it's important.

Prime Meridian is zero degrees longitude, and it splits the world into Eastern and Western Hemispheres.

Prime Meridian is particularly important, because it tells us if we're going east or west.

It also helps us to determine time zones.

Time in countries to the east of the Prime Meridian is always ahead of that in the UK.

And time in countries to the west of Prime Meridian, is always behind, that of the UK.

And the Prime Meridian, runs through Greenwich in London.

But, why is that? Well, in 1884, when Britain was at the height of its imperial power, and had great influence over maritime matters, Greenwich was chosen as the international standard for Prime Meridian.

On my map on the left, I'm showing you the location of the border of Greenwich in London.

Now, before then, before this agreement, countries used to produce map, showing their respective capitols with zero longitude with Prime Meridian running through their capital cities.

This made navigation over long distances, incredibly difficult, because Prime Meridian was in different places, according to different maps.

So on the right, you have a picture that shows Prime Meridian in Greenwich, London.

What is a meridian and why it's important? In this task, what I want you to do, is I want you to fill in the missing blanks using two keywords, which are ahead and behind.

So time in countries to the east of the Prime Meridian is always, is it ahead or is it behind of that in the UK? And then time in countries to the west of the Prime Meridian is always, is it ahead or is that behind of the UK? So at this point, pause the video and complete that task.

Okay, let's see if you've got this one right, I know that you did.

So you could use the word, ahead or behind, and you had to fill in the blanks using the keywords.

First one, time in countries to the east of the Prime Meridian is always ahead of that in the UK.

And time in countries to the west of the Prime Meridian is always behind that of the UK.

Awesome job my friends, well done.

I'm going to leave this answer up, so that you can check your own.

Awesome job, now let's continue.

But in this unit, we're trying to build up our locational knowledge.

So let's use this map to build up our skills.

What I'd like you to do, is to list three countries that are in the Western Hemisphere, and three countries are in the Eastern Hemisphere.

Remember that the red line marks the Prime Meridian.

So, this is the Western Hemisphere here, and this is the Eastern Hemisphere.

So can you name at least three countries that are in the Western Hemisphere, and three countries that are in the Eastern Hemisphere? And that red line marks the Prime Meridian, which runs through, what does it run through? Runs through Greenwich in London.

All right, at this point I'm going to make this graph really big, I'm going to blow it up, so that you can use it.

And I want you to list three countries in the Western Hemisphere and then three countries in the Eastern Hemisphere.

Good luck, have a go.

Now, let's have a look and see, if you managed to get three countries in the Western Hemisphere, and three countries in the Eastern Hemisphere.

So, let's have a look.

So, I chosen these ones, so I have three countries in the Western Hemisphere, I said the United States, Brazil, and then also Mexico.

And then three countries in the Eastern Hemisphere, I chose Australia, I chose India, and I chose Russia.

I nearly chose China, but I decided to go for India instead, ahh.

So again, at this point, pause the video, and check whether you got my answers, but remember there could be more than one answer as well.

Great job my friends, well done.

So now, let's move on.

Why is there a time difference between countries? So, have you ever wondered, why is that? Why that's the case? Why is there a different time in one country compared to another? Well, it's got to do with the Earth's rotation around its axis.

Remember that an axis is a real or an imaginary line through the centre of an object, around which the object turns.

The Sun only shines on the side of the Earth that it is facing.

And this means that it is daytime for the parts of the Earth that have the Sun shining on them.

Conversely, it is night-time for places that are on the opposite side of the Earth, and are in the shade.

So to recap, the rotation of the Earth causes night and day to alternate.

So let's write whether these statements are true or false.

So statement a, the Earth rotates on its axis.

Is that true? Or is that false? Statement b, the Sun only shines on the side of the Earth that it is facing.

And then statement c, it is night-time for the parts of the Earth that have the Sun shining on them, is that true or is that false? So at this point, what I want you to do is pause the video, and then complete that task.

Okay, let's have a look.

So, the Earth rotates on its axis, that is true, good job.

The Sun only shines on the side of the Earth that is facing, that is also true.

C, it is night-time for the parts of the Earth that have the Sun shining on them, that is false.

It would be night-time, it is night-time for places that on the opposite side of the Earth and are in the shade.

It is daytime for the parts of the Earth that have the Sun shining on them.

Awesome job, my friends.

I'm going to leave this answer up so that you can check them against your own.

Now, awesome job my friends, well done.

Let's use this map that we have here, in order to better understand the concepts of Prime Meridian, and how countries to the east are ahead, and countries to the west are behind in time.

So let's pick two countries.

I'm going to zoom my map in, I'm going to make it really, really big.

So, we know that Prime Meridian runs through Greenwich in London.

And we know that any countries that are to the east of Prime Meridian are ahead of time, and that any countries to the west of Prime Meridian are behind of time.

So let's pick for example, Moscow in Russia, which is a Russian capital.

So Moscow, I know is going to be ahead of time, because it is east of Prime Meridian.

And as you can confirm here, by standard time zones, it says that Moscow is three hours ahead of Prime Meridian.

That means that if in London, it was 12:00 at midnight, in Russia it would be 1AM, 2AM, 3AM.

It would be 3AM in the morning, because it's three hours ahead of Prime Meridian.

Conversely, here in Brazil, in Rio de Janeiro, you can see that it's three hours behind Prime Meridian, because it's to the west of Prime Meridian.

So again, if it was midnight in London, then it would be 11:00, 10:00, 9:00, be 9:00 at night in Rio de Janeiro.

So I remember that any countries that are to the east of Prime Meridian, they're going to be ahead of time.

Any countries that are to the west of Prime Meridian, they're going to be behind time of that, of the UK.

I hope that's very clear.

Now let's move on to the next section.

What is a date line? So in the middle of the Pacific Ocean, there's an imaginary line that is called the International Date Line, and this runs, again from the North to South Pole.

And it's almost directly, on the opposite side of the Earth from the Prime Meridian.

So there is Prime Meridian, and here you can see, it's not much of a line, it's quite squiggly, but you have the International Date Line.

Now, the reason why it's so squiggly is because of the geography of certain countries that falls, that are around the International Date Line.

Now the International Date Line was drawn about 130 years ago, and it's officially, it's officially the line that separates two different days on the calendar.

So on one side of the line, it might be Tuesday.

So let's say on this side of the line, it might be Tuesday.

On the other side of the line, it might be Wednesday.

So this is a really important imaginary line, because it helps us to identify what day we are in.

So if you stood on one side of that, and then you hopped over to the other side, you could say you're sort of time travelling, oh, what a funky concept.

And the International Date Line, it runs from the North to the South Pole.

And it's almost directly on the opposite side of the Earth from the Prime Meridian.

So let's complete the sentence now.

You got three words that you can use, you can use Meridian, you could use opposite, or you could use North.

So at this point, pause the video, and then have a go at completing those sentences.

Now let's check it, let's have a look.

So we can use Meridian, opposite and North.

So the International Date Line runs from the North Pole to the South Pole, and it is almost directly on the opposite side of the Earth from the Prime Meridian.

Awesome job my friends, well done.

Again, I'm going to leave this up so that you can check your answer, and compare it against mine.

Now let's look at an example where the International Date Line throws out a really unusual situation.

So on this map, remember that Prime Meridian, it goes through Greenwich, goes through London, and anything to the east is ahead of Prime Meridian, and anything to the west is behind Prime Meridian.

Now, the example that I'm going to give you, comes from the Line Islands, which are part of Kiribati, which is an island nation in the South Pacific.

And so I marked it there in red.

So, lets' zoom in, just to see a little bit clearer.

So 3, 2, 1, and, boom, we zoomed in.

On this map, we can see both the Line Islands, which are here, and you can also see the U.

S.

state of Hawaii.

So they're both islands, and, notice also that placement of the International Date Line, so it's here.

And again, don't be fooled by the idea that International Date Line is a straight line, it is not a straight line.

Now, the placement of the International Date Line means that the time of day on the Line Islands is the same as in Hawaii.

So the time of day is the same, but the date is one day ahead.

So in both examples, it might be mid-day, might be 12:00, but on the Line Islands, it's going to be one day ahead of Hawaii.

And Hawaii is going to be one day behind the Line Islands.

So both places, both Hawaii and the Line Islands, they share the same time of day.

But the Line Islands is one day ahead of Hawaii, and Hawaii is one day behind the Line Islands.

How strange, what a weird concept.

Again, both places have the same time, but they have, they have different date.

Line Islands are one day ahead, Hawaii is one day behind.

And it's all because, it's all due to the fact that the International Date Line is placed right there in such a manner.

Let's go to the next one, how does time difference affect human activity? So, time difference can affect this in many different ways.

And one way is that, when we travel from one place to another, we sometimes feel really tired and sleepy, because we're going into a different time zone, and this is called jet lag.

Now, time difference can also impact business, and the economy.

Sometimes we have to work with people in different countries, in different time zones, and therefore we have to find different ways to communicate with them.

And therefore, time difference affects both business and travel, because you have to take into consideration what time it is in another part of the world when you travel, or when you want to work with someone from there.

And guys, that is the end of our lesson.

So it's now time to compete your end of lesson quiz.