20211223 : tropics

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Now, this is not new information. It is just new to me.

Why am I writing about it?

Because I am happy I found out something which I had taken for granted all along. 

Besides, I am bored and nothing else to do...

All my life, I have known that we in Bangalore have "tropical" weather. I know it is so because it lies between the two lines (tropic of Capricorn and tropic of Cancer).

I had never stopped to ask why the 2 arbitrary lines are there. Surely a km this side or that wouldn't make a big difference to the weather...

And it doesn't. They have nothing to do with the weather. The weather is just a consequence of being there..

If we take a long and narrow pole and erect it perfectly vertical, it will form a shadow based on the time of the day (where the sun is)

At 12 noon, the sun is directly overhead and there is no shadow. 

That is what my textbooks said. The truth is there will still be a shadow depending on the time of the year (tilt of the earth).

That shadow at 12 in the noon, will also change everyday - gradually swinging from long to short and long again on the other side.

Twice in the year, when it crosses over, the shadow becomes zero (the Sun is perfectly on top)

After a distance from the equator (centre), the tilt is too much and it never becomes zero. It just becomes longer and shorter. The Sun is never perfectly on top throughout the year.

The points beyond which it never becomes zero are the 2 tropic lines - not arbitrary as I thought.

And the 2 times it becomes zero in places lying on those lines are the two solistices of the year.

So, if you live in places beyond that point - the sun will never be on top perfectly - hence colder weather.

And if you are on the equator, the Sun is on top perfectly, everyday. Its solistice everyday. Hence warm always...



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