Experiment!: Planning, Implementing and Interpreting

2.3 The Hypothetico-Deductive Method

When the young Isaac Newton was toying with prisms in 1666 he noticed that they dispersed a white beam of sunlight into all the colors of the rainbow. If the colored light from a part of this rainbow was passed through a second prism it did not result in a new rainbow, only in further dispersion of the colored beam. The experiment is described schematically in Figure 2.2. Newton concluded that the prism did not add the rainbow colors to the light. Maybe the white light of a sunbeam already contained all the colors and all the prism did was to spread them out over the wall opposite his window? As a consequence, he thought, re-combining the colors should produce white light [4]. He set up an experiment to do just this and, as most readers are probably aware, his thought was confirmed.

Figure 2.2 Schematic representation of Newton's experimentum crucis. The second prism does not produce rainbow colors, as the first one does. Newton concluded that prisms do not add color to white light, but the colors are constituents of white light.

This is an example of working out the consequence of an hypothesis by logical deduction and testing it by an experiment (although Newton himself would not agree that this is the full story of what he did [4]). An hypothesis can be seen as a preliminary attempt to explain something – a theoretical statement without ...