Discuss how latitude and longitude on Earth are similar to declination and right ascension in the sky.

RA-Dec (Right Ascension and Declination) system is a coordinate system to locate an object on the celestial sphere. It should be noted that RA-Dec of a star or a celestial object remains same for the observer all over the world. This grid is very similar to the grid on the Earth i. e. Longitude - latitude system. One can consider the RA-Dec grid like we extended the long-lat grid and pasted it on the celestial sphere.

Similarities:

1. They both are global and do not change with change in observer's location.

2. Just like equator is reference for latitude, celestial equator is reference for declination.

3. Declination circles are parallel to celestial equator just like latitude circles are parallel to equator.

4. RA lines drawn from north celestial pole to south celestial pole just like longitudinal lines run from north pole to south pole.