Shrinkies

OK, so you can't really shrink people like they show in movies. But here's a fun experiment you can do with something that actually does shrink.

What you'll need:
Foam plastic plates
Scissors
Markers
Foil
Oven set to 350^o
Oven mitts

Cut out small round or rectangular pieces from the flat bottom of the foam plates. Draw pictures on them with the markers. Arrange them on a piece of foil so that they are not touching, and heat in the oven for 4-5 minutes, or until they have shrunk. Take the foil out of the oven carefully using the oven mitts and let the shrinkies cool. You will see a miniaturized version of what you originally drew!

So, why does this kind of shrinking work? The foam has a Swiss-cheese-like structure, with lots of air holes. When you heat the piece of foam, the air bubbles collapse, and you end up with a solid piece of plastic. You have actually changed the density of the plastic, by decreasing the volume, keeping the mass (weight) the same.

Incredible Shrinking Movies

One science theme that shows up in movies from time to time is the ability to shrink things down to a tiny size. The 1957 movie, The Incredible Shrinking Man, didn't use computer graphics because there were no computers at the time! In 1966, Fantastic Voyage told the story of medical professionals who were miniaturized and injected into the bloodstream of a patient so that they could perform surgery on a blood clot. More recently, in Honey, I Shrunk the Kids , a scientist invents a shrinking machine which puts his children, and his neighbor's children, in danger (although they're all OK in the end).

So, what about the science behind these movies? It's not so good - in fact the science is very wrong. It's true that, at normal size, there's a lot of space between the molecules of our bodies. But you can't actually make the molecules smaller; they'd just have to get closer together, and that would start to change the way our bodies work. In science, there's a Law of Conservation of Mass, which means that you wouldn't get any lighter, even if you could get smaller. So you would just become more dense. Just imagine a group of normal-weight people swimming through your blood vessels! These movies may be a lot of fun, but they really are incredible!