(a) linear & b (log-log) Planetary orbital periods versus distance from sun.

perihelion aphelion Geometry of the earth’s orbit. (not to scale.)

Center of sun to Center of earth Relationship of declination angle δ s to tilt of the earth’s axis.

Position (solid lines) of the sun for Vancouver, Canada for various seasons. September 21 and March 23 nearly coincide. Isochrones are dashed. All times are pacific standard time

Flux F through an area A into one side of a volume.

Planck blackbody irradiance,,from the sun.

Planck blackbody irradiance,,from the earth.

Black-body irradiance E* reaching top of Earth’s atmosphere from the sun and irradiance of terrestrial radiation leaving the top of the atmosphere, plotted on log-log graph.

Reduction of radiation across a path due to absorption by particles, illustrating Beer’s law.

Typical diurnal variation of radiative fluxes at the surface. Fluxes are positive upward.

Fate of sunlight en route to the earth’s surface.