ABSTRACT
It is interesting to note that to measure the temperature of the water, Joule observed the position of the top of a column of mercury relative to a scale on his thermometer. To measure the weight of the water and the weight of the falling mass, Joule observed the position of a mechanical pointer relative to a ruler on his scale. In both cases, careful calibration allowed the measured positions to be converted into temperature and weight. Nevertheless, these were fundamentally positions that were being measured, and when the measurements were being made, the column of mercury and the mechanical pointer were stationary and not moving. This tells us that in addition to knowing the position of the top of the column of mercury and the mechanical pointer, Joule also knew their speeds to be zero. This is a very natural part of our experience with nature where we intuitively
9.1 Introduction ........................................................................................................................ 189 9.2 Classical measurement ...................................................................................................... 190 9.3 Quantum measurement .................................................................................................... 192 9.4 Conclusion ..........................................................................................................................200 References ..................................................................................................................................... 201
expect to be able to simultaneously know both the position and speed of an object. For example, as we drive to work, we can read the speedometer while we pass under a bridge. We then simultaneously know the position of the car to be under the bridge, and the speed of the car as reported by the speedometer. While this is a very natural thing for us to expect to always be true, it turns out that it is not. As the scale of an object becomes much smaller than the scale, we can easily observe without specialized tools, a new and surprising picture emerges with regard to what we can measure. This new picture is a consequence of the laws of quantum mechanics as they are used to describe the behavior of particles at these smaller spatial dimensions.
