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Where are we On the Earth
Where is Earth? In the Solar System
In the Solar System, what is Earth doing? We will learn about it through this model.
What is this? This is the Earth.
Actually, a model of the Earth. We call it the GLOBE.
What is this doing See what it is doing
It is revolving How is it revolving?
It is rotating around itself and revolving around the sun.
It is rotating around itself and also around the sun.
Where is the Sun Dharini? Here
Shall we assume this to be the Sun? We know that Sun gives light.
So, since this gives light let's assume this is Sun.
Here, you have just said that the Earth revolves around itself as well as around the sun.
When earth revolves around itself, what is it called?
It is called Earth's rotation. Right. Very Good
So, when earth revolves around its own axis it is called rotation.
Now, see Dharani, what is she doing?
She is rotating.
How is she rotating? She is rotating around herself.
What can we say now?
Can we call his Dharani's rotation? Yes
Why? Because Dharani is rotating around herself.
Now, what if Dharani will rotate around this table.
Earth's revolution...
It is Dharani who is rotating, so, It will be Dharni's revolution.
Similarly, the earth rotates around its own axis which is called rotation.
At the same time it revolves around the sun, it is called revolution.
What is the use of Earth's rotation? How does it benefit us?
It creates Day and Night for us.
How does it happen? Shall we see?
Now Dharani show me, where is Day and where you have night.
Day is here Night is here
Now, because sun is here, the sunlight falls here
This half portion where there is light, it becomes day.
Here it is dark. So this dark portion has night.
Now, let's assume this girl is Dharani.
She is right here on the Earth in India.
Lavanya has gone to America.
Where did she go? America
Where will America be, will it be here or under?
It will be under. Below here.
Here she is
Now see where Dharani is standing what time is it there?
It is 12 noon
It is 12 noon because her head is vertical.
What does Earth do? It keeps rotating.
Now what time is it?
1 PM
Now? 2 PM
Now? 3 PM
Now? 4 PM
Now? 5 PM
Now? 6
Which 6 will it be for Dharani?
6 in the evening.
What about Lavanya? 6 AM
Now if Dharani is seeing the Sun, she sees it setting.
Now if Lavanya is see, She sees the sun rising.
Does the Sun actually go down? No
Does the Sun actually rise? No
Actually what happens is that
the Earth keeps rotating
and this girl is moving from the lit zone to non-lit zone,
and this other girl? She is moving from a non-lit zone to a lit zone
Why does this happen?
Because earth is rotating. Yes, because earth is rotating.
Now, 7 8 9 10 11 and 12
Now, which 12 does Dharani experience?
12 Midnight
And for Lavanya. 12 Noon
With the rotation of the earth we experience Day and Night
Day
Night
Day
Night
Thus, because earth rotates around its own axis, we experience Day and Night
Now what is Earth doing here?
It is revolving around the Sun.
Now, if the Earth is like this, what will be the time?
6 PM
Why? Because sun's rays are slanting.
If it is this way? It is vertical.
Now, you keep observing while I rotate the Earth.
The Earth will be in another position.
After some days will it come here or not?
Now, what time is it for this girl?
12 Noon
12 Noon. Right. Why is it so?
Sun is right above the head.
Now you see, what time is it for this girl now?
12 Noon.
Right, 12 Noon. Why?
Because the sun is vertical, above the head.
Now, if it comes this way, what would be the time?
6' Oclock. Right 6' O'clock. Why is it so?
Because, sun's rays are slanting. From here and from here.
Now, if it is like this what would be the time?
12 Noon
Whenever the sun is right above our head, what will the time be? 12 Noon.
Now, can you tell how many time did Vijay revolve around the sun?
13 times. How is it so?
He claims he has revolved around the sun 13 times.
Let's ask him. Can you tell how ?
It takes one year for Earth to go around the sun. Right. So?
How did you arrive at 13 years?
It is because he is 13 years old. Very Good!
Now, if this girl is here, what would the time be?
6 PM. 6 PM.
Why, because, it is vertical here and here the sun's rays are slanting.
Now, see this girl goes from here to here.
She is standing at this point.
Now, what would be the time for her?
3 PM. And what about this other girl?
3 PM. 3 PM Is it?
Now, see the Earth is rotating like this...
Now, what would be the time for this girl?
6 PM And for this girl?
6 PM again. Are you sure?
Okay. Now what time is it for this girl?
12 Midnight
Then, for this girl?
12 Midnight. 12 Midnight. Is it? Why is it?
Both are on the same line.
That's right. Very good.
They are in the same line. Do you notice these lines on the Earth?
These horizontal lines are called Latitudes.
And the vertical lines are called Longitudes.
Both these two girls are on the same longitude.
Earlier Lavanya said the time here was 3 PM. But is it 3 PM for this girl?
What time is it for this girl? 12 O'clock
And for this girl? 12 O'clock.
As our Earth revolves, when it come here, she should fall right right?
Why doesn't she fall?
Only the Earth is rotating and we are not rotating.
We are on the Earth right? When we come here, why don't we just fall off this way?
When we throw something up, what happens? It falls back.
Why is it so? Due to Earth's Gravitational Force
Now here there is Gum so that girl is stuck
But when we come here why we don't fall is because
What does the Earth keep doing? It pulls us towards itself. So we don't fall.
If we do, where will we fall?
We will fall back on the Earth.
You see SPACE/SKY everyday don't you?
Is it the same or is it different each day?
It is the same. Is it?
Let's see.
It is day here for this girl.
Now during day time how far above can she see the sky?
Can she she only until here or can she see the space above the sun also?
She can see only up till the Sun.
Will the space above the Sun be visible? No.
Now when this girl comes here, what do you say?
This is the leg and this is the head.
Now when her head is here, which part of the sky can she see - the one here or the one here
The one here.
What it means is that she gets to see a different sky during day and a different one at night.
Are we seeing the same part or different portion?
We see different portions (of the sky).
In the same way, when the Earth revolves,
the portion of Sky at night that we see also changes.
During day, it is this and during night it is this.
What month is it now? 4th month.
That is April.
Let's assume that in April Earth is here.
During April, this girl will see this portion during the day. Right?
At night, she will see this portion.
Now after 6 months, May, June, July, August, September, October
When it is October, what is the time now?
12 Noon 12 Noon right?
How much of the sky can this girl see at 12 Noon?
Up till here. Right up till here.
The same way, at night, which part of the sky will the girl see?
The one here or the one here? The one at the top.
So, in October she is seeing this portion,
but during April nights, she sees the stars that are there in this portion of the sky.
But, after six months, she sees this portion.
Then, would it be possible to see the sky that is here? No.
Why? Because the Earth keeps revolving.
So, when the Revolution of the Earth takes place,
the night sky keeps changing for us.
So, with just this one model what did we learn?
Day and Night
Rotation and Revolution
How does the Sun's rays fall on the Earth - Vertical or Slanting...
We learnt all this. Did you understand all of it? Yes we did!