The earth"s tilted axis (23. 50) causes unequal distribution of incoming solar radiation across the planet"s surface, and with it creates the seasons. The earth, in its revolutions around the sun, wobbles between 23. 50 n. (tropic of cancer) and s. latitude (tropic of. During the vernal (spring) and autumnal (fall) equinoxes (march 21, and sept. 23), the sun is closer to the equator, and both hemispheres have identical daylengths. Tropics of cancer and capricorn have a fairly steady input of solar radiation, and thus experience relatively little seasonal variation this area is thus known as the tropics. During the winter solstice in the n. hemisphere, points north of the arctic circle (66. 50. N. ) experience 24-h darkness, points south of the antarctic circle (66. 50 s. ) experience. 24-h daylight (during the summer solstice, this situation is reversed); this creates dramatic physiological challenges for the organisms living in these areas www. notesolution. com.