Friday, November 1, 2013

Horse racing

As mentioned in a previous blog post about climate science, I really don't like horse racing. It's physical and emotional abuse of horses at best. Here are my thoughts from that post:
"I can't stand horse racing. It's simply justified animal abuse in my opinion. If I were to hit you with a whip to make you run faster, I'd surely be done for physical abuse! I've been told however that jockey's don't always hit horses, they pretend to hit them most of the time...which is worse! If I was to pretend to hit you with a whip in order for you to run faster, I could be done for emotional abuse."
I'd like to add to that little rant with this. If there was no-one betting on which horse would win, it wouldn't be a very popular sport, which, by extension, means that the only reason this sport exists, is for gambling, which makes it less like a sport, and more like...gambling! To make some people very rich, and others very sorry that they wasted their money.

Horsehead nebula. We use parallax
to measure Astronomical distances
The only good thing about horse racing is that it uses (or used to) parallax at the finish line to determine the winner of the race. parallax is a very important concept in science and it seems to be left out of a lot of places.

So what is parallax?

Parallax is the observation a fixed object from different perspectives in order to calculate its distance from the observer. The best example is to do it yourself. Put your thumb up and extend your arm out. Make your thumb over up something on the other side of the room, a clock, or light or something and close one eye (it doesn't matter which one). Now keeping your thumb where it is, open the other eye and close the one that was just open. Your thumb has now 'shifted' and it is no longer covering the thing you originally covered. This is parallax. Your point of observation move, therefore the object you were observing appeared to move. With some very simple maths and similar triangles we can calculate how for away the light (or clock...or whatever) is, based on the length of your arm and distance between your eyes.

This is how we measure astronomical distances. We assume that the stars that are a very long way away, don't move much (they do but we don't see it) and we measure a stars position in the night sky in January, then again in July, when the Earth is on the other side of the Sun. the distance that the stars relative position has changed tells us how for away it is. Cool!

The point is though, that if you change where you observe from, you will change your measurement. This is where parallax error comes in. If I measure a volume of liquid standing up, then the same volume of liquid while I am sitting, I'll be observing the liquid from different perspectives therefore giving a different result. Not good!
Japan World cup 2. Horse racing done right!

It's exactly the same with Horse racing. Two people can have different opinions of which horse won a race depending on where the saw the finish line from. Even if they were both next to each other, they would still see the result differently. To get around this, we use a mirror at the finishing post of a horse race.

The mirror helps us eliminate parallax error. The way we do this is to line up the horses nose, with the image of the horses nose in the mirror. When the two things line up, we know for sure that we are looking at the finish post straight on and that will tell us which horse finished first. Lining the object and the image of the object makes sure that we are not changing our perspective. This technique is used in physics all the time to either measure the distance to something, or eliminate observational error.

So next Melbourne cup when we are all experts on horse racing, you'll find me talking about parallax, not the odds of some animal that we make run fast in winning money for us. If I ever owned a horse, I think I'd call it Parallax Error!

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