Ask A Scientist Astronomy Archive

name         Heather S.
status       educator
grade        6-8
location     WA

Question -   Why does the real time of local noon seem to change 
from one month to the next? 
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This is because the Earth's orbit around the Sun is not circular. The
Sun-Earth distance varies from approximately 146 million to 153
million km (91 million to 95 million miles), so the apparent Sun is
early each November and late each February. A further complication is
the tilt of the Earth's axis 23.5° from the orbital plane.

The maximum divergence is 14m 14s in February, and 16m 26s in
November, with secondary 'peaks' of 3m 41s in May and 6m 29s in July.

HOWARD BARNES.
Astronomer.
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