Take a look at this science how-to video to see how to make a homemade compass. It's very easy to build your own DIY compass and is a great science project for the kids.
You only need a few materials: a tea light (candle), a magnet, tape and a bowl of water. Take the candle out of the aluminum housing and tape the magnet into the aluminum can. Now just sit it inside the bowl of water and watch it... is it north or is it south? This is great if you're lost in the wilderness, although I doubt you would have a tea candle on you.
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