![]() Despite Earth being its closest to the sun (yes, this happens in winter - not summer), its axis now points its farthest away from the sun. On December 20 or 21, 6 months after the first day of summer, Earth's orientation has totally reversed. Winter Solstice: Earth leans toward the cold of space.(The opposite applies for the Southern Hemisphere, whose surface is curved farthest away from the Sun.) This means that warmer temperatures and more daylight are experienced there. ![]() As a result, the sun's direct rays strike at the Tropic of Cancer (23.5° north latitude) and heat the Northern Hemisphere more efficiently than any other region on Earth. Observed on June 20 or 21 in the Northern Hemisphere, the summer solstice is the date on which Earth's axis points its innermost towards the sun. Summer Solstice: Earth's max tilt gives us max heat.But if Earth's motions gradually change at each point along its route, why are there only 4 seasons? The four seasons correspond to four unique points where Earth's axis is tilted (1) at a maximum toward the sun, (2) at a maximum away from the sun, and equidistant from the sun (which happens twice). Together, Earth's tilt and trip around the sun create the seasons. (If Earth's axis wasn't tilted, the poles would also be at 90° angles to the sun's radiation and the entire planet would be heated equally.)īecause it greatly affects the intensity of heating, Earth's tilt - not its distance from the sun - is considered to be the primary cause of the 4 seasons. On the contrary, if a region is located slantwise from the sun (for example, like Earth's poles are) the same amount of energy is received, but it intercepts Earth's surface at a shallower angle, resulting in less intense heating. When a region directly faces the sun, sunrays strike the surface head-on, at a 90° angle, delivering concentrated heat. ![]() This tilt controls the strength of sunlight reaching Earth's surface. While journeying around the sun, our planet doesn't "sit" perfectly upright - rather, it leans 23.5° from its axis (the imaginary vertical line through Earth's center which points toward the North Star). (One trip takes approximately 365 1/4 days to complete, sound familiar?) If it wasn't for Earth's orbit, the same side of the planet would directly face the sun and temperatures would remain either perpetually hot or cold year round. How Earth Moves Around the Sun (Earth's Orbit & Axial Tilt)Įarth travels around the Sun on an oval-shaped path known as an orbit. ![]()
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