Pendulum the pendulum could be used to measure the force of gravity. During his expedition to Cayenne, French Guiana in 1671, Jean Richer found that a pendulum clock was minutes per day slower at Cayenne than at Paris. From this he deduced that the force of gravity was lower at Cayenne. In 1687, Isaac Newton in "Principia Mathematica" showed that this was because the Earth was not a true sphere but slightly oblate (flattened at the poles) from the effect of centrifugal force due to its rotation, causing gravity to increase with latitude. Portable pendulums began to be taken on voyages
Which? shops selling hearing aids and an investigation into electronics shop staffs' knowledge of the products that they sell. Other publications include "Which? Travel", "Which? Car", "Which? Money", "Which? Computing" and "Which? Gardening". The Consumer's Association has experienced sharply increased income in recent years as its trading subsidiaries have expanded their activities. Which? regularly briefs and lobbies MPs, Peers, AMs, MLAs, MSPs and MEPs on national, European and international consumer issues. For example, Which? successfully lobbied to put an end to the '65-day rule' that allowed energy companies to wait 65 days before informing their customers of a price change. Following