Because of the Earth's tilt on its axis, the declination of the Sun varies systematically throughout the year.
|Date||Declination of Sun|
|Mar 21st||0 degrees|
|Jun 21st||+23.5 degrees|
|Sep 21st||0 degrees|
|Dec 21st||-23.5 degrees|
Therefore, the path that the Sun takes across the sky varies through the year. Here is what happens in Ithaca:
On June 21st, the Sun is at its highest declination, +23.5 degrees. The path of the Sun on that day is longest, so the length of the daylight hours is longest.
|Can you figure out what happens on Mar 21st and Sept 21st?|
On Dec 21st, the Sun is at its lowest declination, -23.5 degrees. The path of the Sun on that day is shortest, so the length of the daylight hours is shortest.
This means that the noontime altitude of the Sun is different at different times of the year. The Sun transits the meridian at a higher altitude in the summer than in the winter.