Justin Li


Drafting

2009-03-23

Last week's question: Why do things appear smaller when they are further away?

This intriguing problem actually has very little discussion. I found several discussion boards, but the people on there are either really confused or half crazy. The last link is the best explanation, although it was also touched on in the other discussion boards.

But in any case, I figured out the solution before reading the boards. It's nice to have my answers checked though.

What happens is that as objects are further away, the angle it forms in our eyes is smaller. All the light has to pass through a small hole (the pupil for the human eye, some other form of lens for cameras and video recorders) before this gets processed. The larger the angle, the larger than image is. When an object is up close, light from that object forms a very obtuse angle. This translates to a large image. When things are further, however, the angle is smaller. This correspondingly makes the image smaller.

The second part of the question was why this was the case. This is the case because light travels in a straight line. If light curved before entering recording device to make a bigger angle, or otherwise curved after that point and before it hits the retina, then closer objects could appear smaller than large ones. But our vision would also be greatly distorted.

In fact, I wonder if there are animals whose eyes work like this.

This week's question: What are the fluid dynamics of drafting in cycling or driving?

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