Problem
Explain the difference between an experimental law and a hypothesis; give a concrete example in which a hypothesis is not confirmed by the data and therefore has to be modified.
Solution
A hypothesis is a conjecture, that is, a possible explanation or relationship proposed before or during an investigation, which has not yet been tested against the data. It serves as a starting point: it says “let’s suppose things are like this” and indicates which experiments to carry out to check it.
An experimental law, on the other hand, is a relationship between physical quantities that has already been corroborated by a set of reproducible measurements: it is no longer a mere supposition, but a regularity confirmed by experiment within a certain range of validity. In short, the hypothesis stands at the start of the experimental method, while the law is one of its possible outcomes, once the data support it.
Example in which the hypothesis is disproved. Suppose we put forward the hypothesis: “the period of oscillation of a pendulum depends on the mass hung from it”. To check it, we keep the length of the string fixed and measure the period while hanging increasingly larger masses. The data show that the period stays practically constant as the mass varies: the hypothesis is not confirmed. We must therefore reject it or modify it, reformulating it into a version compatible with the measurements, for example: “the period of the pendulum does not depend on the mass, but depends on the length of the string”. This new hypothesis, subjected to further tests and confirmed, becomes an experimental law.
The essential point is methodological: it is the experiment, not intuition, that has the final word. A hypothesis that disagrees with reliable data must be abandoned or corrected.
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Topics: Experimental method