For locations north or south of the equator , the main feature accompanying each season is a change in temperature caused by the varying amount of sunlight that falls on each hemisphere of the Earth throughout its annual orbit. The hemisphere tilted towards the Sun will experience longer hours of sunlight, and more direct sunlight. As the Sun is higher in the sky during summer, the sunlight reaching the surface is more concentrated.
In winter, the Sun is lower in the sky, and sunlight is spread out over a larger area. During spring and autumn, both hemispheres receive about the same amount of sunlight. Furthermore, a large amount of the Sun's energy is scattered before reaching the ground because the energy has to travel through more of the atmosphere.
Therefore near June 21st, the southern hemisphere is having its winter solstice because it "leans" away from the Sun. Advancing 90 days, the Earth is at the autumnal equinox on or about September 21st. As the Earth revolves around the Sun, it gets positioned such that the Sun is directly over the equator. Basically, the Sun's energy is in balance between the northern and southern hemispheres.
The same holds true on the spring equinox near March 21st, as the Sun is once again directly over the equator. Lastly, on the winter solstice near December 21st, the Sun is positioned directly over the Tropic of Capricorn at The southern hemisphere is therefore receiving the direct sunlight, with little scattering of the sun's rays and a high sun angle producing long days.
The northern hemisphere is tipped away from the Sun, producing short days and a low sun angle. What kind of effect does the earth's tilt and subsequent seasons have on our length of daylight defined as sunrise to sunset.
Over the equator, the answer is not much. If you live on or very close to the equator, your daylight would be basically within a few minutes of 12 hours the year around. The daylight difference is subtle in the tropics, but becomes extremely large in the northern latitudes. Where we live in the mid latitudes, daylight ranges from about 15 hours around the summer solstice to near nine hours close to the winter solstice. Moving to the arctic circle at But around the winter solstice, the daylight only lasts slightly more than two hours.
There becomes a profound difference in the length of daylight heading north of the arctic circle. Barrow, Alaska at slightly more than 71 degrees north latitude, lies just less than nautical miles north of the arctic circle.
Barrow sees two months of total darkness, as the Sun never rises for about a month on each side of the winter solstice. The sun does not get cold in the winter. The sun is a giant ball of fire driven by nuclear reactions. The surface of the sun stays at an incredibly hot temperature of about Kelvin all year long. The high temperature of the sun causes it to constantly emit prodigious amounts of thermal radiation in all directions, mostly in the form of infrared waves, visible light, and ultraviolet waves.
This radiation spreads throughout our solar system and warms everything it hits. Regions of earth are colder in the winter because the tilt of the earth causes the sunlight to be spread over a larger area and therefore be weaker per unit area in these regions.
Some people think the earth gets colder in the winter because the earth is farther away from the sun, but this idea is wrong. In fact, the earth is farthest from the sun in the northern hemisphere's summer, and not winter. But distance to the sun does not have much effect on the amount of sunlight the earth receives because the distance to the sun does not really change that much. The earth is about ,, kilometers away from the sun. Over the course of a year, the distance from the earth to the sun changes by at most 5 million kilometers.
To put this in perspective, the orbit of the earth around the sun throughout the year is plotted below to scale.
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