Μήνας: Ιανουάριος 2017

There are many phenomena related to the Moon:

It is known from antiquity that the Moon influences the water masses of oceans, lakes and rivers, producing the tide effect. The variable lunar gravitational attraction on earth surface causes the flood tide, i.e. the rising of water height, and the ebb tide, i.e. the falling of water height.

Newton tried first to explain the tide phenomenon; he also referred to the contribution of sun attraction. It is known now that the tide’s intensity is bigger during the syzygies. The height increase depends also on the morphology of the coastline, the winds, the atmospherical pressure etc. The high tides can produce floods and are dangerous for sailors and fishermen. Therefore, their predictability has always been most valuable.

Διαβάστε περισσότερα “The lunar influence”

The moon phases refer exclusively to the Synodic month, but the necessary time for a full moon revolution round the Earth is approximately 2 days small. How does this happen?

Earth moves: it revolves round the Sun. Therefore, the Earth has moved during the necessary time for the Moon to make a full circle round the Earth (cf. points E and E₁ in figure). When the Moon has moved to point S, its projection on the sky is the same with the corresponding star on the projection point M. Despite its full revolution in the zodiac, the Moon has to move on the small arc S – M₁ to synod with the Earth and the Sun (–> synodic month).

The necessary time interval for Moon to make a full revolution round the Earth and to have the same projection on sky, is called Sidereal month. Its duration is 27,32166 days.

Διαβάστε περισσότερα “The real lunar motion”