Comments from “Ole Rømer og den bevægede Jord – en dansk førsteplads” by Jan Teuber in the book “Ole Rømer – videnskabsmand og samfundstjener”, Gads Forlag 2004 and Erling Poulsen:Here are told that Rømer has “devised”, the article are written by somebody else.
Here the reader must get the impression that it will take light a little less than a second to travel the Earth diameter, this are about twenty times less than what are written later.
If the Earth moves 210 diameters in 42½ hours then it will move 4.94 diameters in one hour and the circumference of the orbit must be 43300 diameters, the radius of the orbit are then 6900 Earth diameters, but from Rømers notebook and from his letters to Huygens we know that he used a distance EarthSun of 12000 Earth diameters. Here we learn that if it takes light one second to travel one Earth diameter (which is very wrong) then it will take 3½ minutes to travel 210 diameters (we learn that 210 seconds equals 3½ minutes, very interesting) and we learn that if two such intervals are added we get nearly half a quarter of an hour.
This cryptic part is difficult to understand but an interpretation could be that the proportion between the velocity of light and the velocity of the Earth is like (40 revolutions of Io seen from one side of the Earth orbit + 40 seen from the other)*42½*60 to 22, this gives 9300 very near today’s value 10000.
If we use this value then we get: Earth velocity = 2π/365.25/24/60 = 1.195*10^{5} AU/min; light 9300 times as fast = 0.111 AU/min or 9 min./AU; on August 23^{rd} 1676 the distance EarthJupiter were 4.408 AU, on November 9^{th} the distance were 5.526 AU, increase 1.118 AU (WinStars 2 is used, but it can be calculated by help of Kepler’s laws), therefore it will happen 9*1.118 =10 minutes later.
This article must have been written by a not so clever scientific journalist.
