Galileo could have simulated his early data on the phases of Venus

Abstract

Galileo claimed the phases of Venus as his own discovery. His priority claim hinges on the authenticity of his December 1610 record of observations ostensibly dating back to October. Scholars have argued that Galileo’s report must be truthful, since it is too accurate and detailed to have been forged after the fact. However, I show that Galileo could easily have forged these data by means of a basic simulation with a physical sphere rather than actual observations. This calls into question the received view that Galileo must have known about the phases of Venus already before it was brought to his attention by others.