Ole Roemer was born in Denmark on September 25th 1644 and died in Copenhagen, Denmark on September 19th 1710. He later enrolled in the University of Copenhagen in 1662. In this part of his life he met Rasmus Bartholin who was the first to publish his discovery of the double light refraction. When Ole Roemer he had a huge opportunity to study mathematics and astronomy through Tycho Brahe’s previous observations. However Ole went through a long series of jobs before he decided to study astronomy such as astronomer royal, director of the observatory, master of the mint, inspector of naval architecture, harbor surveyor, ballistics expert amd professor of mathematics at the University of Copenhagen. At this time in history very few astronomers even believed that there was a finite speed that light travelled at, most simply believed that it was instantaneous. Roemer was able to accurately determine the speed of light through very careful measurements over long periods of time. The way that Roemer went about calculating the speed of light was through observations of the eclipses of Jupiter’s moons. He realized by looking at the observations of himself and Brahe that the eclipses either took place about 10 minutes earlier or later than they were predicted to, depending on the distance from the Earth to Jupiter. When Jupiter was closest to the Earth he noticed that they were about 10 minutes earlier than the calculations had predicted and while Jupiter was farthest away from the Earth he noticed that they occurred about 10 minutes later than they were predicted to. This led him to the realization that light had a finite speed, which few believed at that time. This made him conclude that light moves at a speed of 142,500 miles per second. The accepted value of light speed today is around 192,500. His estimation was the most accurate at the time. Ole Roemer also contributed to other improvements in his time. He was the inventor of the first street lights in Copenhagen. This was the start of a social reform. In Copenhagen, Roemer made rules for building
new houses, got the city's water supply and sewers back in order, ensured that the city's fire
department got new and better equipment, and was the moving force behind the planning and making
of new pavement in the streets and on the city squares
