6 July

1687: On 6 July 1687, Newton's Philosophiae Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy) was published for the frist time. This work is often held to represent the culmination of the 'Scientific Revolution', in which science as we know it today was born.

Among the concepts originated by Newton and appearing in the Principia, the most important is that of 'mass,' introduced and named in Definition 1 of the Principia. In this work, he also describes the three 'Laws of Motion,' and also the first appearance in print of Newton's invention of calculus.

1476: On 6 July 1476, Regiomontanus died.

Regiomontanus was a German astronomer and mathematician. In January 1472, he made observations of a comet which were accurate enough to allow it to be identified with Comet Halley comet 210 years later. He also observed several eclipses of the Moon.

His interest in the motion of the Moon led him to make the important observation that the method of lunar distances could be used to determine longitude at sea. However, instruments of the time lacked the necessary accuracy to use the method.