Christians Huygens Christian Huygens (1629 to 1695) was probably the greatest Dutch scientist of his time. He was primarily a mathematician and physicist but also made contributions to astronomy using his own designed telescopes), biology (through his discoveries using microscopes of his own making), and the construction of clocks. He was the son of Constantin Huygens a famous poet and influential statesman and diplomat under the Dutch Republic. He had two other brothers and sisters. Being from an aristocratic family he was educated in languages (including French and Latin) drawing, law, science, engineering, mathematics and music. He is known to have said “science is my religion” (see Cosmos by Sagan pg 143). The Huygens family had many distinguished guests visiting the including Descartes. Huygens also had contact with Spinoza although he did keep this relationship polite but distant (he loaned Spinoza books and Spinoza did work grinding lenses for Huygens). Huygens had contact with other great scientists of his time including Gottfried Leibnitz who visited Huygens to study mathematics with Huygens. Huygens was also a member of French Academy of Science as well as the Royal Society in its early days. He kept an active correspondence with the members of the Royal Society including Isaac Newton, and Robert Hooke. He was greatly admired within these scientific communities. In the field of astronomy Huygens was one of the first to discover the rings of Saturn. He invented the pendulum clock that he hoped could be used to accurately measure time on ships in the opens seas. At this time navigation at sea had a very high priority for trade as well as for military strategy. Note: The idea of longitude is based on the fact that the earth rotates on its axis once every 24 hours. This means that it moves a total of 360 degrees in 24 hours meaning that each hour is equivalent to 15 degrees of longitude. An idea that came from Galileo was to use the moons of Jupiter as a reference point to record the time at any given geographical point on the earth and thereby observe its position at the local time. The difference in the apparent position of the reference point at a specific time in the local area could be used to calculate the longitude compared with a 0 geographical position i.e. the prime meridian. Accurate navigation required the determination of longitude which was not yet known. Therefore governments greatly encouraged the development of such clocks since longitude at sea could be calculated if one knew the time difference between two different geographic positions using a fixed reference point (e.g. position of the sun). Despite Huygen’s efforts the first chronometer that could accurately measure time at sea was invented by a clockmaker John Harrison in 1760. He developed a wave theory to describe the nature of light. Huygens considered that light behaved as if it travelled in waves in a vacuum similar to waves on the ocean. This differed from Newton’s idea that light was composed of particles. Red light was made up of larger particles than blue light. Actually both turned out to be right. Einstein later showed that a particle theory of light could explain the photoelectric effect (that a light beam shinning on a metal surface could knock off electrons). Modern quantum mechanics considers both the light behaves if it is composed of particles and as if it is composed of waves. He made early progress in describing the moving bodies and their collisions but never published them. Centrifugal force and gravity Huygens through experimentation with measuring the motion of pendulums, discovered that they exhibited constant acceleration. Through this work he derived formulas describe this motion and came also to describe motion in terms of centrifugal force around 1647. He saw that centrifugal force and gravity were related (today called the equivalence of gravity and inertial mass). He estimated “g” (the constant for the force of gravity) at 9.8 m/sec2. These discoveries were made independent of Isaac Newton. Discoveries in Astronomy Huygens believed as did Copernicus that the Earth moves around the Sun. This was widely accepted even by ordinary people in Holland at that time. Huygens even mentioned that Copernicus was acknowledged by all astronomers accept those who “were a bit slow witted or under superstitions imposed by merely human authority” (see Cosmos by Sagan pg 145). Christian philosophers during the middle ages argued that the heavens circled the Earth once a day and that it was not infinite in extent and therefore the existence of an infinite number or even a large number of worlds was not possible. The discovery that the Earth and not the sky moving and profound implications with respect to how unique the Earth was considered and whether there was life on other planets. Copernicus thought that the entire universe was heliocentric and Johannes Kepler did not think that stars had planetary systems. Huygens believed in the existence of other inhabitable worlds in the universe. Before he died in 1690, he published a book entitled “The Celestial Worlds Discover’d: Conjectures Concernng the Inhabitants, Plants and Productions of the Worlds in the Planets. In this book Huygens even speculated as to how the inhabitants of these other worlds would look . Huygens maintained that science was his religion and that the planets in the universe must be inhabited otherwise God had created them for nothing.