How do we distinguish between a valid result and an artifact created by that apparatus? … He [Hacking] pointed out that even though an experimental apparatus is laden with, at the very least, the theory of the apparatus, observations remain robust despite changes in the theory of the apparatus or in the theory of the phenomenon. …Observing the predicted effect strengthens our belief in both the proper operation of the microscope and in the observation.
Hacking correctly argues that it would be a preposterous coincidence if the same pattern of dots were produced in two totally different kinds of physical systems. Different apparatuses have different backgrounds and systematic errors, making the coincidence, if it is an artifact, most unlikely. If it is a correct result, and the instruments are working properly, the coincidence of results is understandable.
The Skeptic's Guide to Physics:
As fallible as your own judgement may be, it is the only authority you can trust. So make sure you can trust it! Tolerate no confusion, no uncertainty, no obscurity. Be skeptical of everything you read until you have thought it through and satisfied yourself that it is indeed correct. If you successfully cultivate this habit, you will be a Physicist.
mp3: Iron Maiden - Run to the hills