The video is being made. Until it arrives, here is what it will say (117 words, about 58 seconds):

Here's a cat asleep on a windowsill, in the sunshine. The sill is warm, but nothing hot has touched it.

Now let's go indoors at night. A lamp has been on all evening. A boy switches it off, brushes the bulb by accident, and ouch, it's hot!

The lamp is for giving light. So why is the bulb hot?

And now let's step outside on a frosty morning. A girl's hands are cold. She rubs them together, and they warm up.

Three warm things. Where did the warmth come from each time?

That's this topic: light, and the warmth that comes with it.

Okay, so are you ready to find out why the sunny windowsill is warm?

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