Thank you for the opportunity to help you with your question!
A solar noon is defined when the Sun is directly above.because the Earth revolves round the Sun, the point that is above would always have changed because earth is in a different position
from the previous noon.
the earth's orbit is not a circle but an eclipe it travels in a high speed when in contact to the sun and more slow when far from
the sun. The duration from solar noon to solar noon is a sidereal
day,in addition,the time it takes to compensate
for how long it has traveled in its orbit Please let me know if you need any clarification. I'm always happy to answer your questions.