Wednesday 21 March 2012

Why Is It Dark In Other Countries When It Is Light Here?

What Garden Girl really asked me was, 'Why does Uncle M only get out of bed when we are already having lunch?' He currently lives in Peru and consequently there is a 5 hour time difference. In order to explain why this is, the best thing to do is get a ball and a torch, but I also used this diagram:

The earth is shaped like a ball and hangs in space. But it doesn't stay still. Although we can't feel it moving, the earth is spinning all the time. It never stops. It takes a full day (24 hours) for the earth to spin around once. I put a sticker on a ball to represent Garden Girl and showed her that as the earth spins, so does she. When the sticker is on the same side as the torch, light from the torch can reach the sticker. It is day time for the sticker when the torch light shines on it. When the ball has turned half way around, the torch light cannot reach the sticker so it is dark and night time for the sticker.

It is the same for our house. When our house is facing the sun, the sun light can reach us and it is daytime. When the earth has moved halfway around and our house is on the side facing away from the sun, the sunlight cannot reach our house. It is dark and it is night time.

Because people live all around the earth in different countries, as the earth spins around, the sun hits different countries at different times, so Uncle M wakes up 5 hours after us because that is when his house has just started to turn towards the sun.

I put a few stickers on the ball, in different locations, to show Garden Girl how one sticker might still be in the torch light, while another one is just entering the torch light, and yet another might still be in the dark. I asked her to tell me which sticker would be the next to wake up and to spot a sticker that will soon be going to bed. It was a fun activitiy that illustrated, not just that one side of the earth is light while the other side is awake, but that also showed how light arrives at different times for different countries.

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