The orbital daylight/darkness cycle

gkell1

The Earth has two distinct daylight/darkness cycles,one arising from the daily rotation of the Earth and the other from the specific way the Earth orbits the Sun hence,in the absence of daily rotation,all locations on the planet would experience a single day/night cycle over the course of a year in the absence of daily rotation.

At the North South poles ,where daily rotation is residual,they experience 6 months of daylight followed by 6 months of darkness while at the equinox,the polar coordinates either enter or exit the circle of illumination as the planet slowly and unevenly turns to the central Sun while moving around its orbital circumference.

The original explanation for the seasons by Copernicus relied on variable 'tilt' to the Sun whereas the new explanation introduces an additional daylight/darkness cycle arising from the orbital behavior of the Earth,the original De Revolutionibus hypothesis being flawed -

"..the equator and the earth's axis must be understood to have a variable inclination. For if they stayed at a constant angle, and were affected exclusively by the motion of the centre, no inequality of days and nights would be observed. On the contrary,it day or the day of equal daylight and darkness, or summer or winter, or whatever the character of the season, it would remain identical and unchanged." Copernicus

To the contemporary mind,we now take for granted with human habitation at the South pole,the experience of 6 months of daylight followed by 6 months of darkness presents no real difficulty to recognize yet ,as it is a single cycle where daily rotation plays no part,requires an explanation borrowed from the Earth's orbital motion around the Sun.It would not have been so obvious to people 400 years ago and indeed up until recently but taking the wider view opens up an entirely different approach to explaining the temperature fluctuations between July and January,that somewhere on the planet it is orbital noon and another place orbital midnight (the poles experience that at the Solstice) and why natural noon cycles vary when allied with steady daily rotation.

It is a fairly new modification so unfamiliarity is the only real obstacle until readers think the issue through.