The traditional explanation for the cause of seasons I have heard is that because of the angle of the axis of the Earth with respect to the ecliptic, the angle at which light rays hit the Earth's surface at a fixed latitude changes through the year, and hence the ray density changes (the ray density changing as $\cos({\theta})$). So when the Sun is higher up in the sky in summer, the ray density on the surface of the Earth is higher and the intensity of light is higher compared to winter.

However, how important is the fact that the Sun's light passes through more air (and hence is scattered/absorbed more) when the Sun is lower above the horizon in winter compared to summer? Isn't this also a factor contributing to the summer nun being 'stronger' than the winter sun? How important is this factor compared to the ray density changes when trying to explain the causes of the seasons?

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    $\begingroup$ Another consideration might be the shortening/lengthening of days $\endgroup$
    – Topcode
    Jun 25 at 22:03
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    $\begingroup$ I suspect the answer is “very little”, since the sunlight absorbed or scattered by the longer path length doesn’t disappear; it mostly either ends up hitting the ground anyway (if it’s scattered) or heats up the air (if it’s absorbed). $\endgroup$ Jun 26 at 12:24
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    $\begingroup$ This might be better suited to Earth Science $\endgroup$ Jun 26 at 15:22


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