Wednesday, November 4, 2009

Swords and Candles

This is really about Hollywood swordsmen but movie pirates are always champion fencers so it sort of applies.

How often has this scene been shot - two swordsmen are about to fight. The villain turns and cuts through a candlestick. The hero makes a swish and appears to miss. He stomps his foot and the candle falls.

So, can this be done? I experimented with this years ago. I discovered two things. First, you cannot cut through a regular candle. The sword is stopped by the wick. There just isn't any way around this. It is difficult to cut a string with a sword. If it is under a load and you have the right stroke then you can do it but it takes a slicing stroke. You can't do this with a candle because of the wax. You have to cut the wax with a straight cut. If you try slicing it, the wax will stick and the candle will go flying.

So, you have to have a special candle with no wick. If you make one of these then it is possible to cut through the candle with one stroke. Thinner blades work better. A machete worked better than a sword.

So that's the first part. The second part is - can you slice through a candle so well that it will not show the cut? This part is impossible.

Think about the physics involved. No matter how sharp your edge is, the rest of the blade takes up space - up to a quarter of an inch. Two solids cannot occupy the same space at once so the candle has to move enough to let the blade pass through. If you could do this very slowly then gravity might pull the top half of the candle back in place but then the sword would not have enough energy to slice the candle in the first place. Instead you have to make a very fast strike. That is going to send the top half flying. There just isn't any other possibility.

This is also true when cutting people (although I have not tried this). The movies Equilibrium and Underworld both have sword fights where someone's head is cut but he doesn't realize it until his face slides off. It can't happen.

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