Machine learning (ML) and artificial intelligence (AI) algorithms are now being used to automate the discovery of physics principles and governing equations from measurement data alone. However, positing a universal physical law from data is challenging without simultaneously proposing an accompanying discrepancy model to account for the inevitable mismatch between theory and measurements. By revisiting the classic problem of modeling falling objects of different size and mass, we highlight a number of subtle and nuanced issues that must be addressed by modern datadriven methods for the automated discovery of physics. Specifically, we show that measurement noise and complex secondary physical mechanisms, such as unsteady fluid drag forces, can obscure the underlying law of gravitation, leading to an erroneous model. Without proposing an appropriate discrepancy model to handle these drag forces, the data supports an Aristotelian, versus a Galilean, theory of gravitation. Using the sparse identification of nonlinear dynamics (SINDy) algorithm, with the additional assumption that each separate falling object is governed by the same physical law, we are able to identify a viable discrepancy model to account for the fluid dynamic forces that explain the mismatch between a posited universal law of gravity and the measurement data. This work highlights the fact that the simple application of ML/AI will generally be insufficient to extract universal physical laws without further modification.1. Introduction. The ability to derive governing equations and physical principles has been a hallmark feature of scientific discovery and technological progress throughout human history. Even before the scientific revolution, the Ptolemaic doctrine of the perfect circle [1, 2] provided a principled decomposition of planetary motion into a hierarchy of circles, i.e. a bona fide theory for planetary motion. The scientific revolution and the resulting development of calculus provided the mathematical framework and language to precisely describe scientific principles, including gravitation, fluid dynamics, electromagnetism, quantum mechanics, etc. With advances in data science over the past few decades, principled methods are emerging for such scientific discovery from time-series measurements alone. Indeed, across the engineering, physical and biological sciences, significant advances in sensor and measurement technologies have afforded unprecedented new opportunities for scientific exploration. Despite its rapid advancements and wide-spread deployment, machine learning (ML) and artificial intelligence (AI) algorithms for scientific discovery face significant challenges and limitations, including noisy and corrupt data, latent variables, multiscale physics, and the tendency for overfitting. In this manuscript, we revisit one of the classic problems of physics considered by Galileo and Newton, that of falling objects and gravitation. We demonstrate that a sparse regression framework is ideally suited for physics discovery, highlighting ...