 Objectivity in science is an attempt to uncover truths about the natural world by eliminating personal biases, emotions, and false beliefs. It is often linked to observation as part of the scientific method. It is thus intimately related to the aim of testability and reproducibility. To be considered objective, the results of measurement must be communicated from person to person, and then demonstrated for third parties, as an advance in a collective understanding of the world. Such demonstrable knowledge has ordinarily conferred demonstrable powers of prediction or technology. The problem of philosophical objectivity is contrasted with personal subjectivity, sometimes exacerbated by the overgeneralization of a hypothesis to the whole. Newton's law of universal gravitation appears to be the norm for the attraction between celestial bodies, but it was later superseded by the more general theory of relativity. Another methodological aspect is the avoidance of bias, which can involve cognitive bias, cultural bias, or sampling bias. Biases for avoiding or overcoming such biases include random sampling and double-blind trials. However, objectivity in measurement can be unobtainable in certain circumstances. Even the most quantitative social sciences such as economics employ measures that are constructs conventions, to employ the term coin by Pierre Duhamp, for instance, one can use different weighting schemes when calculating inflation rates. Applying different conventions such as the POSC and LASPARDS indexes leads to obtaining diverging results.