Why seasons swap hemispheres.
Why is winter here summer somewhere else?
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Why is winter here summer somewhere else?
Move Earth around its circular orbit and compare hemispheres.
Earth’s tilted axis keeps nearly the same direction as Earth orbits the Sun. A hemisphere tilted toward the Sun receives more direct light and longer days. The opposite hemisphere receives shorter days. Distance from the Sun does not explain these opposite seasons.
Circular orbit, fixed parallel axis. Declination asin(sin tilt×cos orbit angle); daylight from solar hour angle at ±latitude. Refraction and seasonal lag omitted. Seasons are due to tilt, not orbital distance.
Give the northern hemisphere a longer summer day than the southern hemisphere.
Compare daylight in opposite hemispheres.