Antarctica gets sunlight
For a long time the people of Qaanaaq endured in complete darkness. Now, in mid-February, the moment has come that they have been looking forward to for months. Despite the freezing cold of minus 35 degrees Celsius, they gathered at lunchtime. When the first rays of sunshine shine on their faces, people sing a song in the old tradition and throw their hats in the air.
Qaanaaq is one of the northernmost settlements in the world. It is located at the extreme point of Greenland, just south of the 78th parallel. Around 600 people, most of them Inuit, live here - almost four months a year in complete darkness. In winter it is the polar night, the sun stays behind the horizon around the clock. In the summer it does not go under for four months. It seems only flat, but at least the temperatures climb above freezing during these months. In between there are months in the twilight when it is neither day nor night. The seasons in Qaanaaq cannot be compared to ours.
The mirror sun
Thomas Schuler has a problem similar to that of the Inuit: For four months there was no sun on his farm. However, he does not live far in the north, but deep in the Black Forest, in Simonswald. There the sun rises every day even in winter, but it only drags a flat path across the sky. Too flat for the Schuler's farm, which is surrounded by the ridges of the Black Forest. In winter these cast shadows for so long that no ray of sunshine reaches the courtyard all day. But the resourceful inventor knew what to do: he installed a large mirror on the opposite mountain slope. Now at least a little sunlight shines through the window even in winter.
Polar regions - Arctic and Antarctic
The largest ice sheets on earth are around the North Pole and the South Pole. Because of their special location, the polar regions receive very little sunlight and solar heat, and the summers are particularly short there. That is why it is always extremely cold there - temperatures of down to minus 70 degrees Celsius prevail all year round. The cold caused huge ice masses to form in the polar regions.
The ice of the Arctic around the North Pole covers a large part of the Arctic Ocean in winter. It then extends over an area of several million square kilometers. For the most part, it is a layer of ice that floats on the sea. In addition, the Arctic ice covers the northern areas of Europe, Asia and North America.
On the other hand is the South Pole on a continent that Antarctic. Antarctica is the coldest place on earth. Their landmass is almost completely buried under an armor of ice and snow that is up to 4 kilometers thick. Almost three quarters of the fresh water on earth is stored in this ice.
People, animals and plants have adapted to life in the "eternal ice". Polar bears or reindeer, for example, protect themselves against the cold with a layer of fat and thick fur. The Antarctic is inhabited by only a few people, the Arctic is a little more populated. The most famous inhabitants of the Arctic are the Inuit in North America and Greenland, there are also the Lapps in northern Scandinavia and indigenous peoples in northern Siberia. They used to live there as nomads and get around with dog sleds. Today they use snowmobiles and many of them live in cities.
Hardly anything grows in the ice deserts around the poles because of the extreme cold. The ground between the polar regions and the cold-temperate zone is permanently frozen to a great depth. After the Latin word “permanere” for “to last”, this subsurface is also called permafrost. It only thaws a little a few months a year. Then particularly hardened plants such as mosses, lichens or dwarf shrubs can grow on it. This region around the polar regions is also called subpolar tundra.
The polar regions are the coldest areas on earth. It is precisely here that the earth is heating up: For several years now, researchers have been observing that the ice masses of the Arctic and Antarctic are melting. The consequences of this warming cannot yet be precisely estimated. But it is already clear that many habitats are threatened by the melting of the poles.
Why are our days different in length?
In summer we look forward to long days and short nights, in winter, on the other hand, it gets dark in the afternoon. And around the North and South Poles there are even areas where the sun does not rise or set for months. So day and night can be of different lengths - but why?
We experience day and night because the earth is a ball that rotates: When our place of residence rotates into the illuminated area, it becomes day; when it turns out again, night.
In addition, the earth's axis is crooked: for half a year the northern hemisphere tilted towards the sun, while the other half the southern hemisphere.
If you look at how the tilted globe is illuminated by the sun, you can see that the northern and southern hemispheres are not evenly illuminated. When our northern hemisphere is inclined towards the sun, the illuminated area there is larger than in the southern hemisphere. As a result, the place in which we live turns into sunlight earlier and out again later. So our day is longer than in the southern hemisphere.
The longest day is when the northern hemisphere has tilted the most towards the sun. That is always the case on June 21st. In Stuttgart, for example, there are around sixteen hours between sunrise and sunset. Then the days get shorter again, which is why one speaks of the summer solstice.
It is the other way around when the northern hemisphere is tilted furthest away from the sun. This winter solstice happens exactly half an orbit (i.e. half a year) later, on December 21st. In Stuttgart, the sun can only be seen for about eight hours.
March 21st and September 22nd are exactly in the middle between the solstices. On these days, day and night last exactly the same length (namely twelve hours), which is why they are called equinoxes.
The closer you get to the equator, the smaller the differences become. And exactly at the equator, day and night always last twelve hours.
The situation around the North Pole is completely different: it is inclined towards the sun for half a year, so that it is continuously bright there for half a year. The other half year the North Pole tilted backwards. A six-month “polar day” is followed by an equally long “polar night”. The area around the North Pole, where there are days when the sun does not rise or set, is called the Arctic Circle. The same thing happens around the South Pole, only with the seasons reversed: it is day at the North Pole, night at the South Pole, and vice versa.
Why is the sun differently high in the sky?
On hot summer days you can look forward to a cool shade, but in winter you don't want to stand in the shade and freeze. But the world is unfair: In summer, of all places, the shadows are short, because the sun is high in the sky. And in winter the sun is so low that even small hills cast long shadows. But why is the sun actually differently high in the sky?
In reality, the sun is always in the same place, at the center of the solar system. Only from our point of view does it look like the sun is coming from different directions. That's because we live on a sphere.
How the light from the sun arrives on the globe depends on where you stand on this globe. If you stand exactly on the "belly", that is, the point that is directed exactly towards the sun, the light rays hit the surface of the sphere at exactly right angles. So the sun is exactly over you in the sky.
If you go north from there, the surface of the earth curves away from the sun. Therefore, the rays of the sun no longer hit at a right angle, but at an angle from the south. From the earth, the sun is no longer exactly above you, but something in the south.
And the further north you go, the flatter the rays of light hit, that is, the lower the sun is above the horizon. If, on the other hand, you go south from the “belly”, the opposite is true: the sun seems to come from the north, and the flatter the further south you go.
But that's not all: Since the earth's axis is crooked, our position in relation to the sun changes over the course of a year. In summer, when the northern hemisphere is tilted towards the sun, we are closer to our “belly”. The sun's rays therefore hit the earth at a steeper angle and the sun is higher in the sky. In winter, on the other hand, the northern hemisphere has tilted away from the sun and we are further away from the “belly”. The light then hits the earth flatter and the sun is lower in the sky.
In addition, the earth also rotates, and so there is a second movement every day: During the day, the sun moves from east to west across the sky - more or less high above the horizon, depending on the season.
Why are there seasons?
We enjoy the first warm rays of sunshine in spring, look forward to swimming pool visits in summer and trudge through colorful foliage in autumn. In December at the latest we get our thick sweaters out of the closet, because in the winter months it can get really cold - and mostly it snows too. The seasons influence our life, but also that of plants and animals. But how does this change of seasons come about?
The most noticeable difference between the seasons: it's warm in summer and cold in winter. Most of the heat comes from the sun, so the difference between summer and winter must have something to do with the sun.
In fact, there are several reasons: In summer the days are long and the nights short. The air and the ground therefore have a lot of time to warm up during the day in summer and only cool down a little during the short night. In winter it is the other way round: the sun only brings a little warmth for a short time, while the long nights cool the air and the ground.
In addition, the warming rays of the sun are weaker in winter. Compared to summer, the sun is lower in the sky. The rays of the sun hit the ground more flat. This distributes the sunlight over a larger area, so that each individual spot on the ground receives less light and heat. In addition, the flat rays of the sun have to travel a longer distance through the atmosphere, and more energy is lost.
In summer, on the other hand, the sun is high in the sky. The light rays hit the ground steeply and bring a lot of warmth with them.
But while we look forward to the warm summer in the northern hemisphere, it is winter in the southern hemisphere. Because whether the sun is high or low in the sky and whether the days are long or short depends on whether the northern or southern hemisphere is inclined towards the sun.
In the vicinity of the equator, the length of the day and the position of the sun change little over the course of the year, so it is tropical hot all year round.
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