Ole Rømer
Videos
Ole Christensen Rømer was a Danish astronomer who, in 1676, first demonstrated that light travels at a finite speed. Rømer also invented the modern thermometer showing the temperature between two fixe
Ole Rømer, portrait by Jacob Coning from c. 1700
Rundetårn ("round tower") in Copenhagen, on top of which the university had its observatory from the mid 17th century until the mid 19th century when it was moved to new premises. The current observatory there was built in the 20th century to serve amateurs.
Ole Rømer at work
Meridian circle
Videos
The meridian circle is an instrument for timing of the passage of stars across the local meridian, an event known as a culmination, while at the same time measuring their angular distance from the nad
Ole Rømer
…is 8 minutes and 19 seconds, and a speed of 299,792,458 m/s. In addition to inventing the first street lights in Copenhagen, Rømer also invented the meridian circle, the altazimuth, and the passage instrument (also known as the transit instrument, a type of meridian circle whose horizontal axis is not fixed in the…
Groombridge transit circle of 1806
Meridian circle at Saint Petersburg Kunstkamera, built by T.L. Ertel, Germany, 1828
Meridian circle at the Kuffner observatory, Vienna, Austria, built by Repsold & Sons, Hamburg, 1886. Note the counterweights, the short, green cylindrical objects at the outer top of the mechanism, and the four long, thin, microscopes for reading the circles.
Meridian circle at the Quito Astronomical Observatory. Built by Repsold & Sons, Hamburg, 1889.