How many sidereal days are there during 1 tropicy year?
The sidereal day is the time taken for the same star to return to the meridian (due south for the observer), and is about 23 hours and 56 minutes (4 minutes shorter than the solar day due to the Earth’s orbital motion around the Sun). The tropical year is the one used for civil purposes, and is basically the one that keeps the seasons on the same dates each year. This contrasts with the sidereal year which would have the same constellations forever visible on the same dates (for example Orion more or less due South on December nights), but you would end up sowing your crops in October, and is considered less convenient for society. In 12000 years you will see Orion in June. There is only about 15 minutes difference between the 2 alternative ‘years’, and therefore, approximately 366.25 sidereal days in an average tropical year rather than the 365.25 solar days.
