<P> The rotation constants have been measured by measuring the motion of various features ( `` tracers '' ) on the solar surface . The first and most widely used tracers are sunspots . Though sunspots had been observed since ancient times , it was only when the telescope came into use that they were observed to turn with the Sun , and thus the period of the solar rotation could be defined . The English scholar Thomas Harriot was probably the first to observe sunspots telescopically as evidenced by a drawing in his notebook dated December 8 , 1610 , and the first published observations ( June 1611 ) entitled `` De Maculis in Sole Observatis , et Apparente earum cum Sole Conversione Narratio '' ( `` Narration on Spots Observed on the Sun and their Apparent Rotation with the Sun '' ) were by Johannes Fabricius who had been systematically observing the spots for a few months and had noted also their movement across the solar disc . This can be considered the first observational evidence of the solar rotation . Christopher Scheiner ( `` Rosa Ursine sive solis '' , book 4 , part 2 , 1630 ) was the first to measure the equatorial rotation rate of the Sun and noticed that the rotation at higher latitudes is slower , so he can be considered the discoverer of solar differential rotation . </P>
<P> The rotation constants have been measured by measuring the motion of various features ( `` tracers '' ) on the solar surface . The first and most widely used tracers are sunspots . Though sunspots had been observed since ancient times , it was only when the telescope came into use that they were observed to turn with the Sun , and thus the period of the solar rotation could be defined . The English scholar Thomas Harriot was probably the first to observe sunspots telescopically as evidenced by a drawing in his notebook dated December 8 , 1610 , and the first published observations ( June 1611 ) entitled `` De Maculis in Sole Observatis , et Apparente earum cum Sole Conversione Narratio '' ( `` Narration on Spots Observed on the Sun and their Apparent Rotation with the Sun '' ) were by Johannes Fabricius who had been systematically observing the spots for a few months and had noted also their movement across the solar disc . This can be considered the first observational evidence of the solar rotation . Christopher Scheiner ( `` Rosa Ursine sive solis '' , book 4 , part 2 , 1630 ) was the first to measure the equatorial rotation rate of the Sun and noticed that the rotation at higher latitudes is slower , so he can be considered the discoverer of solar differential rotation . </P>
when was it discovered that the sun rotates
when was it discovered that the sun rotates
1630
1630