That circle of latitude is called the Arctic Circle. Earth on June This is the date of the summer solstice in the Northern Hemisphere. Note that as Earth turns on its axis the line connecting the North and South Poles , the North Pole is in constant sunlight while the South Pole is veiled in 24 hours of darkness. The Sun is at the zenith for observers on the Tropic of Cancer. Many early cultures scheduled special events around the summer solstice to celebrate the longest days and thank their gods for making the weather warm.
In spring, the Sun will rise farther and farther north of east, and set farther and farther north of west, reaching the maximum around the summer solstice. Now look at the South Pole in [link]. The situation is reversed 6 months later, about December 21 the date of the winter solstice , or the first day of winter in the Northern Hemisphere , as shown in [link]. Now it is the Arctic Circle that has the hour night and the Antarctic Circle that has the midnight Sun.
Days are longer in the Southern Hemisphere and shorter in the north. In the United States and Southern Europe, there may be only 9 or 10 hours of sunshine during the day. It is winter in the Northern Hemisphere and summer in the Southern Hemisphere. Earth on December This is the date of the winter solstice in the Northern Hemisphere. Now the North Pole is in darkness for 24 hours and the South Pole is illuminated.
The Sun is at the zenith for observers on the Tropic of Capricorn and thus is low in the sky for the residents of the Northern Hemisphere. As you can see in [link] , the Tropic of Cancer is the latitude for which the Sun is directly overhead on the summer solstice. If Earth were tilted a bit less, then the Tropic of Cancer would be at a lower latitude, closer to the equator. The Arctic Circle marks the southernmost latitude for which the day length is 24 hours on the day of the summer solstice.
If Earth were tilted a bit less, then the Arctic Circle would move farther North. What would be the effect on the seasons and the locations of the Tropic of Cancer and Arctic Circle? What, then, would be the difference in latitude between the Arctic Circle and the Tropic of Cancer? Many cultures that developed some distance north of the equator have a celebration around December 21 to help people deal with the depressing lack of sunlight and the often dangerously cold temperatures.
Originally, this was often a time for huddling with family and friends, for sharing the reserves of food and drink, and for rituals asking the gods to return the light and heat and turn the cycle of the seasons around. Many cultures constructed elaborate devices for anticipating when the shortest day of the year was coming. Stonehenge in England, built long before the invention of writing, is probably one such device. In our own time, we continue the winter solstice tradition with various holiday celebrations around that December date.
Halfway between the solstices, on about March 21 and September 21, the Sun is on the celestial equator. Every place on Earth then receives roughly 12 hours of sunshine and 12 hours of night. The points where the Sun crosses the celestial equator are called the vernal spring and autumnal fall equinoxes.
The seasonal effects are different at different latitudes on Earth. These are the latitudes where the Sun is directly overhead at noon once a year. These solstice days are the days with the most for Summer or fewest for Winter hours of sunlight during the whole year. The Sun is directly overhead at "high-noon" on Summer Solstice at the latitude called the Tropic of Cancer.
Credit: Przemyslaw Idzkiewicz, via Wikipedia Commons. The Sun is directly overhead at "high-noon" on Winter Solstice at the latitude called the Tropic of Capricorn. The Sun is directly overhead at "high-noon" on the equator twice per year, at the two equinoxes. Except at the equator, the equinoxes are the only dates with equal daylight and dark.
At the equator, all days of the year have the same number of hours of light and dark. Between the two tropics zones, which includes the equator, the Sun is directly overhead twice per year. Outside the tropic zones, whether to the south or north, the Sun is never directly overhead.
In particular, when we combine them, we can immediately see why our analemma looks like an "8" that's pinched on one narrow side. As the Earth rotates on its axis and orbits the Sun in an ellipse, the Sun's apparent position Here on Earth, perihelion occurs on January 3rd: just 2 weeks after the December solstice. All told, we can combine these effects to make an equation for where the Sun will be located at any particular time as viewed from any location on Earth.
We call this derived quantity the equation of time. The equation of time is determined by both the shape of a planet's orbit and its axial tilt, as well All told, it's only axial tilt and ellipticity that determine the shape of the Sun's path as viewed at the same time, every day, from Earth.
The Earth's analemma is fixed in this particular shape. But there are two more factors at play in determining the exact orientation of the analemma. One is your location on Earth: observers from the Northern Hemisphere will see the small analemma loop occur high in the sky and the large loop occur lower in the sky, while Southern Hemisphere observers will see the reverse. If you photograph the Sun every day at noon, your analemma will appear perfectly vertical left.
These images are further proof, for any doubters out there, that the Earth is round. And the other is at what time of day you take your photographs. If you take your daily photograph:. Over the course of a day year, the Sun appears to move not only up-and-down in the sky, as When both effects are combined, the pinched figure-8 that results is known as an analemma. It's easy to see that the topmost point corresponds to the summer solstice, while the lowest point corresponds to the winter solstice, but there is no special astronomical significance to the "crossing-point" in the Sun's analemma as seen from Earth.
Occurring approximately on April 14th and August 30th, those dates are only determined by the way our seasons, determined by axial tilt, align with our planet's orbit around the Sun.
If our perihelion and aphelion were aligned with the equinoxes, rather than the solstices, we'd have a teardrop-shaped analemma, rather than a figure-8, which is how the Sun appears from Mars! The analemma is the beautiful, natural shape traced out by the Sun over time, creating a figure-8 as both our orbit and axial tilt dictate. This is a BETA experience. You may opt-out by clicking here. More From Forbes. Nov 10, , pm EST.
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