 He was the first to explain the tides using the attraction of the moon.In 1586, he demonstrated that two objects of different weight fall down with exactly the same acceleration.The first mention of equal temperament related to the twelfth root of two in the West appeared in Simon Stevin's unfinished manuscript "Van de Spiegheling der singconst "(ca 1605) published posthumously three hundred years later in 1884; however, due to insufficient accuracy of his calculation, many of the numbers (for string length) he obtained were off by one or two units from the correct values.