Welcome! In this class we’ll start with

NCERT Class 6 Chapter 2, that’s globe understanding the globe. The longitude and the Latitudes.

Now, we’ll first start of latitude and longitude. We’ll move forward with understanding time

zone calculating time zones and the concept of daylight saving now to start with when

we talk about globe. Let’s take this ball as an example of globe and you have a point

here. The light which runs through this point would be the axis for this globe. Assuming

this to be a globe the top most region would be the north pole and the south most region

would be the south pole so we understand the basic terms when we talk about globe is the

axis north pole and the south pole. Now, I can say globe is representation of the real

earth on a small scale so when we are trying to understand this that helps us in drawing,

maps, projections etc. which we’ll see further. Now, understanding the concept of latitudes

and longitudes. Now, I can see this is a kind of Sphere that means it is 360 degrees. So,

you have the time or the excesses 360 Degrees and around these 360 degrees you have the

24 hours that are calculated so when simplifying this, I can say 15 Degrees would be equal

to 1 hour. So, you have 15 degrees as equal to 1 hour and you would have 1 degree equivalent

to 4 minutes, we will see how we use this as we move further. Now, when we talk about

on to the basic concept of the degrees, minutes and seconds we have one degree which equals

to 60 minutes. One minute which equals to 66 seconds. So, that’s the basic criteria

we’ll use as we move across in this lecture. Now, if I try to understand with the help

of this ball. I can see the lines which are drawn horizontally would be the parallels.

So, because we call these parallels also the latitudes. Now, let’s take the simple palace

in which this ball is divided. So, you have 1 parallel that is running here another 2

parallels are running here. So, there is a zone which is green which is remarked at it

by the other 2 zones. So, I can say this zone is the zone which is close to the zero degree

parallel or the parallel that runs through the centre of the earth. And this zone which

runs north and south of the zero degree that’s we call it as equator is known as the Torrid

Zone so all this green would be the Torrid Zone. Now, let’s try to understand here

in this diagram. So, you have the zero degree which is the equator north and south of equator

you have two major learning that are important both in the north hemisphere and the South

Hemisphere. So, you have the equator north of it 23 degrees north. You have the tropic

of cancer and 23 and ½ degrees south you have tropic of Capricorn then you have 66

and ½ degrees south the Antarctica circle and in the north you have the optic circle.

Now, the region between tropic of cancer and tropic of Capricorn that’s 23 degrees north

south of equator would be known as the Torrid Zone. The region between tropic of cancer

and arctic circle in the north and Capricorn and Antarctica surf and Antarctica circle

in the south would be known as the temperate zone since the temperature would be moderate

and finally arctic circle to south pole that 66 and ½ to 90 degrees north and south would

be known as the frigid zones so, these are the cool zones. Now, these zones are important

to understand when we talk about in terms of the heat and the atmospheric circulation

which we have already covered in the classes on climatology. So, if we try to divide earth

into various zones you have 3basic zones that’s the torrid temperate zone and the Frigid Zone

towards the poles the lines that run parallel to the earth that’s horizontally are known

as latitudes or parallels and these learn east to west. So, these are some the basic

characteristics that we try to understand about latitudes also when you have a latitude

here. All the latitudes north of it would be known as north latitude, all the latitudes

south of it would be known as south latitude. The south most region would be the South Pole;

the North Pole region would be the north pole. Now, in a simple way I rotate this ball and

you can see you have a line that runs vertically north to south. So, lines which run vertically

not to south are known as longitudes. So, you have lines running north-south direction

and these are known as longitudes. Longitudes are also known as meridians. So, as we see

here you can have 360 lines that cover this complete circle. So, you have one degree line

for 360 degrees, so one degree will include 4 minutes. So, you would have 4, 4, 4 minutes

for 360 degrees. So, if we calculate that as we see you saw in the previous calculations

you would have 24 hours and we say 1 rotation is completed in 24 hours so, you have the

longitudes I have the longitude I repeat which are known as meridians there run north and

south. The meridian which runs zero degree is known as the prime meridian or the Greenwich

Meridian. It is taken as the standard reference point now a days this Greenwich meridian is

called as UTC that’s the co-ordinated universal time and if this is zero degree the line directly

opposite to it which is one would be 180 degrees and this 180 degree line would be known as

international date line & why we call it dateline is because as we move east or west from the

dateline you have the date that changes. So, if I say today is 4th of august here it would

be 5th of august so you would have changes in the day as you cross the international

date line not so the case with the Greenwich meridian okay? so, understanding this you

have a simple diagram to explain here now I have some point which are given here for

a very simple explanation if I want to seek I can say point A and point B are on the same

vertical line since they are on the same vertical line point A and B are on the same. Longitude

because longitude runs perpendicular again you would have C and D would have the same

longitude. So, A and B would have a common longitude C and D would have common longitude.

However, now let’s talk about the latitude A and E. So, this 1 and this 1 are running

on the same horizontal line since they are running on the same horizontal line, they

would have same latitude or they are on the same parallel. Longitudes as we said are also

known as meridians and there are north to south. So, all lines all points which are

the same north-south point would have same constitute or same meridian. All the points

which are on the same latitude same parallel would be known as the points on the same latitude

and they run east to west. Now, whenever we talk about the horizontal lines there are

some basic things which are very important. as I said I’ll complete earth coverers 360

degrees so let’s take the ball gain I start from this ball again. So, you have this is

the excess point so, I take this here. This is the zero degree and this whole cover 360.

So, half of it would be 180 and half of it would be 180. Now, this would be 180 east

and this would be 180 west. So, this whole region would be west and this whole region

would be east. First of all, when we talk about time zones it’s important to understand

that in time zone you have this which occurs as the centre of the time zone. So, if I talk

about zero degree Greenwich meridian. It’s the centre reference point which runs from

7 and ½ degree and 7 and ½ degree west. So, the whole region 7 and ½ degree east

and 7 and ½ degree west would have common time and that common time would be equalized

or I would say would be standardized at zero degree. Which is the reference point and that

reference point is known as Greenwich meridian. Now, as we talked about the international

dateline which is 180 degrees and this separates 2 consecutive calendar days now this line

has been bent. Now, originally all the meridians that we talked about cross in a perfect meridian

and they do not have any bends except the international dateline. Now, the only reasons

there are bends in the international dateline is attributed to accommodate the island nation

and the small territories. So, that there is a same time within the complete country

and there is no different time within the same country. Again, there was the problem

with the international dateline accommodating Samoa so you had old international datelines

that cross this region later on this international dateline was modified to accommodate Samoa

island and it was this point on the globe, if we see you would have the changes in the

international dateline that took place so this is about the basics of latitude and longitude.

Now, coming to the standard time zones as I said 360 degrees contribute to 24 hours

so you would have 50 degrees which would contribute to 1 hour so every 15 degree meridian would

be 1 hour so I can also say in one degree would be equation to 4 minutes. Now, in India

the extension runs from 68 degrees east to 97 degrees east nearly. So, the total time

zone the total time difference between say Dwarka in the west to the blue here in the

east would be around 1 hour and 54 minutes. However, in India we have standardized the

company time with a single time zone that is 82 and ½ degrees and this 82 and ½ degrees

east is ahead of Greenwich Meridian by 5 hours 30 minutes. So, in simple terms if I say if

in London at Greenwich the local time is saying 2 P.M. the time in India would be at the same

movement would be plus 5:30 to 2 means in the 2 P.M. you would add 5 hours and 30 minutes

more. So, local time would be 7:30 P.M. so, if there is a live match that is going on

in London at 2 P.M. in India you would see it at 7:30 P.M. So, that’s to understand

how we try to calculate the time zone difference with a very fundamental example. Now, here

is something that we will try to explain and elaborate on the concept of time zones. So,

what I have drawn here is the sheet for the time zone and what I am trying to explain

here is understanding the time zones with respect to 2 different concepts one is if

I know earth’s time in a particular time zone. I can find the time in another time

zone the next day if I know the time in the particular time zone and I am having a flight

of say 8 hours or 10 hours and I have to calculate the time in another part when I reach I could

do that so there can be 2 types of calculations that could be involved here. Now, 1st of all

the zero degree is a Greenwich Time that I have taken into consideration. Now, east of

the Greenwich would be 15 degrees for each line so I have just skipped one by one and

written the time. So, it’s 30 degree East then 45, 60 degrees, 90 degrees and so on.

Till you reach 180 degrees and again this 180 degree and this 180 degree is a common

line but since I’m drawing it on paper and marking these 2 lines on both the edges. Now,

there are 2 things which will try to understand when we talk about time zone let’s say at

30 degrees east the local time is 2:00 P.M. I need to find out the local time at 90 degrees

east. How can I do that? As I know with every 15 degrees there is a difference of 1 time

zone and all that is towards the east would be addition or ahead and all towards the west

would be subtraction or loss of time. So, if it is 2:00 P.M. here, at 45 degrees it

would be 3 P.M. at 60 degrees it would be 4:00 P.M. at 75 degrees it would be 5 P.M.

and at 90 degrees it would be 6:00 P.M. So, if I know the time at 30 degrees east which

is 2:00 P.M. I can straight forwardly calculate the time at 90 degrees east which would be

6 P.M. now, that’s one way the other way around would be if I know the time here is

say 5:00 P.M. and the time here would be 9:00 P.M. so, what is the difference between the

time zone so, when I’m having such a question I have to see whether the values are towards

the east or the west since the both the values is 30 degrees east and 90 degrees east and

you have 1 time is 5:00 P.M. and another time is 9:00 P.M. I will simply do the subtraction

of 2 times that’s minus so, 9 minus 5 would be 4 so the difference between the time zone

would be 4 hours. Now, if I have another case which I take as say let’s say 30 degrees

west and 30 degrees east. Now, I have the time which is 5:00 P.M. here I am moving backwards.

So, it would be 4:00 P.M., 3:00 P.M., 2:00 P.M. and 1:00 P.M. okay? So, if it is 5:00

P.M. at 30 degrees east it would be 1:00 P.M. at 30 degree west so, what I’m doing here

is if I know the time zones say let’s say here the time zone is -2 because it’s this

is -1 , this is -2. Okay? And here it’s +1 and +2 and here the time zone is +2. So,

what is the difference between the 2 time zones. Since it’s crossing the Greenwich

meridian you would have to add these 2 values and the time difference would again be 4 hours.

We have the time difference here, which is 2 + 3 + 4 + 5 and + 6 okay? So, if we calculate

that ways you had the time zones here as plus 2 and plus 6 and the difference of (6 – 2)

would be 4 again, okay? You can take the difference by the time itself or the time zones I am

doing it either base. So, the first example explains about the time the 2nd example explains

about the time zone. So, if you are using the time zones, you have say +2 time zone

and +6 time zone the difference would be 4 again. Here you have +2 time zone and -2 time

zone and the difference would be 4 hours again. Let’s understand how so if we run on the

number line let’s say zero. I jump 1 and 2 here and then 3, 4, 5 and 6. So, if we work

for a simple number line for say the lower grid standard students say 4th & 5th standard

students they can easily understand that from 2 if I am jumping onto six there is a difference

of 4. Now, moving onto including the negative number line in the same concept what would

happen. It would be as simple as that i am having +2 time zone here and -2 time zone

here. So, this would be my total jump and i can say it would be 1, 2, 3 and 4 again.

So, this is the simple way to understand when you cross the Greenwich you have to add the

difference between 2 time zones. However, if the values are on the same of Greenwich

be it east or be it west. You would have to subtract the time zones to find out the time

difference. So, that is one way of calculation. Now, let’s work around some examples that

will help you better understand how we work around the time zones. So, let’s say you

have an example where you have 120 degrees west you have a time which is 4 P.M. so, at

120 degrees west you have 4 P.M. now, you have to find out the time at 90 degrees east

how can we do that it’s as simple as that. So, as you move east you are adding so it

would be 5 P.M., 6 P.M., 7 P.M., 8 P.M., 9 P.M., 10 P.M., 11 P.M., 12 noon. Okay? Then

12 noon you would have a shift in the day. So, if it is 4th June it would become 5th

June here and then again you would have 1, 2, 3, 4, 5 and 6. So, it would be 6 A.M. here.

So, if the time is 4 P.M. at 20 degrees west it would become 6 A.M. at 90 degrees east.

So, that’s the kind of very simple calculation I did. Now, let’s complicate it a bit further.

I’ll include the flight time suppose I’m boarding a flight from 120 degrees west again

the same location at the same time say 4 P.M. my flight duration is 6 hours, at what time

I will reach zero degrees. That’s London or the Greenwich meridian here. Now, how do

I calculate this and starting at 4 P.M. my flight time is 6 hours that means that 6 hours

are lost in the air. So, you would have the starting point as 10 P.M. Now, I move till

0 degree what would be the time? It would be 10 P.M., 11 P.M., 12 Midnight, then 1 A.M.,

2 A.M., 3 A.M., 4 A.M., 5 A.M. and 6 A.M. So, I’ll reach zero degree London at 6 A.M.

So, if I’m boarding today I’ll reach tomorrow 6 A.M. So, that’s one concept that you need

to understand. Now, the next important concept is the concept of Dateline. So, when we talk

about Dateline it’s important to understand how we move around the Dateline so, when we

move around to the west of the date line and to the east of the dateline there is a difference.

So, let’s say I start with 105 degrees west and you have 5 P.M. So, you have 105 degrees

5 P.M. is the local time here. Okay? And the date line is saying 8th August. Now, what

would happen now, let’s calculate when would happen when I cross it towards the west and

then we’ll see what would happen when we cross it towards the east. Now, this is the

international Dateline and again this is the same international Dateline we are drawing

it at 2 different locations and we will see how it works around when we cross the international

dateline. Now, when I’m crossing the international Dateline. I’m starting with 5 P.M. it becomes

4 P.M. I’m going back. So, I’m going west I’m losing time so, you have 5 P.M., 4 P.M.,

3 P.M., 2 P.M., 1 P.M. and 12 noon at 180 degrees state line It’s 12 noon. Now, try

to understand as I said we are talking this as a range between 7.5 degrees east and 7.5

degrees west and this whole region would be zero degrees or zero time zone and then you

would have the next time here which would start from here that would be +1. Okay? So,

here again till this point it would be 12 noon and since the day here is 8th August.

What would happen as soon as I cross this the half of the section here it Would be 12

noon and as soon as I will cross beyond it. it would become 9th august so, you would have

a day that would be added as I move there because let’s move this way and then you’ll

understand why we are adjusting the day and it is important to adjusting the days and

why it is important to exist the days at international dateline. Now, the same example let’s go

east so, I have 5:00 P.M., 6:00 P.M., 7:00 P.M., 8:00 P.M., 9:00 P.M., 10:00 P.m., 11:00

P.M. and 12:00 midnight at 12:00 Midnight it automatically changes the day. So, 8th

August would here become 9th August. Now, I want 9th August. Okay? This region was 9th

of August this region is again 9th of August It’s 12:00 Midnight. Now, I’m going further

east. So, it would be adding few more hours. So, 1:00 A.M., 2 A.M., 3 A.M., 4 A.M., 5 A.M.,

6, 7, 8, 9, 10, 11 and 12 Noon and now this 12 Noon till the point I reach here it would

be 9th of August of 12th noon but as soon as I cross the International Dateline towards

the east, I lose a day. That means beyond 180 degrees east it becomes 8th of august

and that is true because we can see here it was 8th of August since I am talking about

the globe. Now, let’s develop a perspective on the globe itself. So, you have 180 degrees.

Let’s say this is 180 degrees and this is zero degrees and starting from the back. I’m

starting somewhere here which is 5:00 P.M. I’m trying to go east. So, it’s 105 degrees

west which is here, somewhere here I am trying to cross the state line towards the east.

So, this is 8th of August I’ll reach the Meridian and I make 9th of August and as soon

as I reach on the other side it should again when I cross it becomes 8th of august. So

as to maintain a common date on the globe. Otherwise, there would be no end to the expansion

of the dates that we do. So, it’s important to understand that since we are on one globe

there should be common time that should happen and that can only happen if you have say this

point which is 180 degrees. If I cross it towards east, I’ll lose a day if I cross

this towards the west, I gain a day. That means if I’m on 9th of August on this side

as soon as I cross the Dateline it becomes 8th of August and this whole region would

remain 8th of august till the midnight of a till the midnight when I reach the Greenwich

and there is a change in time. So, it would become 9th of August. So, in simple terms

I can say how could be 8th of August and how could be 9th of August and when it will rotate

it would shift. So, that’s the basic ides which we try to explain or understand. Here,

now the next thing that is very important is the time zones that I spread across the

country. Now, if we just talk about the mainland itself Russia has the maximum number of time

zones with 11 time zones. However, if we talk about the mainland and its territories across

the globe you would have France that tops the list and France has 12 time zones because

of the territories that are spread throughout the world. So, you have the main France which

is UTC-1. Then you have the territories of French Polynesia here. You have the territories

of French and southern level islands in south of Africa and then towards the Micronesian

and Melanesian island groups. So, all these together if we talk about the expansion of

French territories France have total 12 time zones. However, if we talk about the mainland.

The maximum number of time zones are visible in Russia with 11 time zones. Now, there is

another important concept that you must understand while you are trying to understand the concept

of latitude, longitude and time zones the concept is daylight saving time. Now, daylight

saving time is also known as summer time and when we try to understand summertime in simple

terms it is setting a clock one hour ahead so as to save the daylight. So, it’s mainly

common towards the polar regions not the equatorial bend towards the polar region, what happens

is you would have longer during summers and shorter days during winters. So, to absorb

more and more sunlight for the longer day, what is the best idea is to increase the day

time so you set your clocks 1 hour ahead and you can take the maximum advantage of the

natural light that is coming in this would reduce the burden of the artificial sunlight.

Now, this concept was first introduced at thunder bay in Ontario in Canada in 1908.

However, it was commonly most popularly said that this concept came into origin with Germany

in 1916 and in 2016. We are celebrating a century of daylight saving time. Now, the

countries which are marked in orange are the countries of the northern hemisphere that

follow daylight saving time the countries marked and blue are the countries of south

hemisphere that follow daylight saving time. The countries which are lighter grey in colour

never ever had a daylight saving time. However, the countries which are marked in dark grey

colour at some point of time they use daylight saving but now they are not using the concept

of daylight savings. So, it’s not a kind of very popular concept it usually starts

in around march and April and ends from somewhere between September to November the basic idea

is you are setting your clocks forward during the spring as a result the daylight saving

time starts early and you lose 1 hour. However, during the fall you set your clocks 1 hour

behind and you regain 1 hour. So, it’s a concept that used mainly by the polar countries

to absorb more and more daylight and daylight time and the sunlight during the summers when

they have longer summer days. So, this was a basic idea to introduce you to the concept

of latitude and longitude. So, this we cover the chapter 2 of NCERT in class 6 as I said

we are covering these topics in a bit detail as those given in the NCERT. So that they

are more useful for your upcoming competitive examination. We’ll be covering the remaining

topics of NCERT in our further lectures those who are interested in NCERT series can definitely

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