At some point in my life, I became a big fan of beer. I don't mean the beer that comes in three-dimensional, easily stacked structures, or the beer that lets you know when it's
cold (that deserves a post to itself, although not about the technology behind the indicator, but about the psychology of the people who are actually attracted to it) but the thousands of small breweries around the country, and out of the country, that make and bottle stuff in small quantities. In the end, on the kitchen counter there is invariably a small pile of bottle caps getting ready to do absolutely nothing. Now there's no shortage of
creative uses for these caps, but the way I see it, there's no nobler than to play a role in teaching a child something about our physical world.
The things you need for this little experiment are:
- sewing needle (a pin is okay too, but not one with a plastic head, it's oddly balanced)
- a cold one
- bowl or dish
- water
- refrigerator magnet (or any magnet really, including an electromagnet)
From the above discussion it looks might hypocritical to have a Heineken in the photo, you'll just have to forgive me and not tell anyone. The first thing you want to do is to use the needle to demonstrate how delicate the vitreous body of the human eyeball is. Kidding. Stroke the needle, in one direction only, across one of the magnetic poles. The way to see how the magnet is oriented is simple: just get the magnet near the needle, and see to which side the point of the needle is most attracted. There will be two such points on diametrically opposing sides of the magnet.
It's important not to draw the needle in both directions; pick one direction, and lift the needle, reposition, and repeat. Keep in mind that there are instructions on the internet that say to rub the needle with silk-this is dead wrong. After you've done 40-50 strokes of the needle, take a break and have the cold one. But, when you open it, be very careful to remove the cap by prying up evenly all around the rim-this will leave a cap that's nicely symmetric, and looking like a mini tart tin.
Now, take the needle, and lay it in the middle of the upturned top, and carefully float this in the bowl of water. Within a minute or so, the magnetized needle will align itself with the earth's magnetic field (remember to move the refrigerator magnet away from the bowl!).
