Lecture 11: Radiometry & Photometry (28)
Ankur

Just wanted to add onto Professor Ng's explanation of the seasons--the reason we know that the Earth's tilt is what causes is seasons is also because the days get longer in the summer and shorter in the winter. Aside from the Sun's rays hitting the surface more directly and causing warming weather, the tilt makes it such that the Northern hemisphere receives sunlight for more hours in the day during the Summer.

One way to intuitively think about this is that if the Earth were at a 90 degree tilt (with the North pole facing the sun), then there must be a season when there's light on the pole for 24 hours and a season when there's light on the pole for 0 hours in a day.

ZizhengTai

Kind of off-topic, but this graph reminds me about how sun light is actually almost perfectly modeled by the Lambert law, since the sun is so far away from us and thus sun light rays are basically parallel when they reach earth.

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