Quantum MeasurementMeasurement |
MeasurementPhysics versus Natural Philosophy
Later in the 19th century the use of mathematical relations in formulating physical theories became very common. In this way, the study of physics became more and more quantitative and its theoretical formulation became more mathematical. (See a page from Einstein's publication.) By the beginning of the twentieth-century partly because of the mathematical complexities of theoretical physics and partly because of the instrumental complexities of experimental physics few scientists could fill both of these shoes. This resulted in creation of two separate "branches of physics": Experimental and Theoretical. The primary task of the experimentalists is to perform experiments and make measurements and quantifications. The theorists use these results and try to infer relationships among the measured quantities. They also try to determine the consequences of these inferences by predicting results of yet to be performed experiments. (A somewhat of an aside to our present discussion, this distinction between theory and experiment has, within the past century, been used and miss-used for political reasons! See the notes on Max Born's famous lecture!)
Process of Quantification - VariablesOf course, in order to make a measurement we first need to specify what is that we want to measure. The quantity that we want to measure must not only be measurable, but its value must also be re-measurable. Without this "repeatability" of the measurement our results would go against one of the most important requirements of scientific method: "empirical replication". (For a good description of scientific method see the site at University of Rochester.) Another important aspect of measurement is the process and the tools of the measurement. Once we have decided what is that we want to measure we need to specify a means of making the measurement. The aim of the process of the measurement has to include a sound means for the measurement. It must also result in production of a reliable outcome. This is what we call experimental procedure. We expect that once the same procedure is followed by others the same outcome is reached. We also expect that different, yet sound, procedures produce the same results too. Among different procedures the one that gives us smallest systematic error is considered superior.
Perfection of InstrumentIn order to quantify an observation we also need to come up with (build, beg, or borrow) an instrument for our measurement. The importance of the instrument is not just in its ability to make the measurement, but also for the precision of the results it could render. A superior instrument is one that measures with a high degree of precision. In fact, at times, the availability of good experimental apparatus allows for success and discovery, while its absence may result in "failure". So, a major task of the experimentalists is to perfect their tools of measurement. In the field of observational astronomy, for example, the availability of the Hubble Space Telescope has, literally, created a new universe just in the last few years. Similarly, the recent study of nano-sciences begun with the invention of a new "microscope", the Scanning Electron Microscope.
SummaryIn summary, the reliance of physics on quantification is the primary factor for its separation from natural philosophy. One could go so far as to state that if "it" is not quantifiable, it is not physics! This strong restriction forces us to closely examine the requirements for a sound quantification. One of these requirements is that when we employ different procedures, the value of variables which we measure should produce closely agreeing results . Another is that in order to obtain results with higher and higher precision we have to employ more clever procedures and better instruments for our measurements. Next, we need to discuss variations in the value of our results due to "errors" in the measurement. How could we reduce, or better yet eliminate, all errors? Could we continue to improve on the precision of our measurement so long as we work harder and harder in the lab? |