Sense of Scale part 2

A common way to put things in perspective is to literally line them up, side by side. We’re visual creatures. We like to see, not imagine abstract numbers. To our brains, a million, billion, and trillion all seem like large, vague numbers.
Apple knows this. Many of its ads compare products to everyday objects, rather than touting the raw dimensions:
The Macbook Air fits into a manilla envelope. The ipod nano is as thick as a pencil. Certain cameras fit in a box of altoids. You know their size without busting out a ruler. Just yesterday, I got a haircut with the #5 clippers (”As wide as your finger”) and knew what it meant. The hairdresser didn’t have to say “.875 inches”.
It seems backwards that “casual” measurements like a pencil’s width can be more useful than a count of millimeters. But we’re not machines — our everyday experience is with pencils, not millimeters, and we can easily imagine how much room a pencil takes.

Source: Mental Math Shortcuts