Why is the sun shining
The effect of sunlight
It's unimaginably hot inside the sun: it's 15 million degrees. After all, it is still 5,600 degrees Celsius on the surface of the sun. This means that the sun is incandescent and appears to our eyes as a white ball.
Without the sun there would be no life on this planet, at least not as we know it today. The sun is a gigantic source of energy that radiates light and warmth into space. Some of their radiation also reaches the earth. This energy warms our atmosphere, the earth and the oceans.
The sun heats up the area around the equator the most, because there its rays hit a relatively small area perpendicularly. The poles, on the other hand, reach the sun's rays at a flatter angle. Here the solar energy is therefore distributed over a larger area; and in these regions it stays cooler. The different levels of solar radiation ensure different climate zones. Seasons and weather are also the result of different levels of solar radiation.
If the earth were to store all of the solar energy, it would be unbearably hot here in no time. This can already be felt on a hot summer day when the temperature climbs to 30 degrees Celsius in a very short time after sunrise. In order for the climate to remain stable for centuries, the earth has to get rid of about the same amount of solar energy.
This happens through the radiation of the earth into space. About a third of the solar energy is immediately reflected back from the atmosphere, land area, bodies of water and ice masses. The earth initially absorbs the rest of the energy in the form of heat. It then slowly releases this heat back into space in all directions.
What is our solar system and how did it come about?
The earth is not alone in space: people have been observing the sun, moon and stars in the sky for a long time. They discovered early on that some stars are moving. These wandering stars were observed and their paths followed. For a long time, however, their movements were not understood - until about five hundred years ago a man by the name of Nicolaus Copernicus solved the riddle: The earth and the "wandering stars" are actually planets that all circle the sun at different distances.
Today we know eight planets. To remember their names in the correct order, the first letters of the sentence "M.a Vater eclarifies mir jEden S.monday uurens Nachthimmel. “- or in short: M-V-E-M-J-S-U-N.
M.Erkur is the planet that orbits closest to the sun. Then come Venus, E.rde and M.ars. These four inner planets have a solid surface made of rock and are still relatively close to the sun - only a few hundred million kilometers.
They are circling further out, at a distance of about one to 4.5 billion kilometers from the sun outer planets: Jupiter, S.aturn with his rings, Uranus and all the way outside Neptun. They are made of gas (mostly hydrogen and helium) and are much larger than the inner planets. Jupiter and Saturn are about ten times the size of the earth, that's why they are also called that Gas giants.
And finally there are asteroids, comets, and clouds of dust that also orbit the sun. The gravitational pull of the sun holds all these heavenly bodies together and forces them to fly in a circle like on a long line. Everything together is called that Solar system. The moons are one of them - but they are held in place by the gravitational pull of the planets.
But why does the sun even have planets? This has to do with how the sun came into being: a cloud of gas and dust contracted by its own gravity and became a star. But not all of the material in this cloud was "built into" the star - around one percent was left over. And when the sun began to shine, the radiation pushed the remaining matter outwards again.
The light gases were pushed far outwards, the heavier dust and rocks remained close to the sun. From these clouds of dust and gas, the planets emerged over time. Therefore there are the gas planets outside in the solar system, further inside the rock planets - including our earth - and in the very center the sun. It contains 99% of the mass of the solar system and holds everything together with its gravity.
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”, ie the point that is directed exactly towards the sun, the rays of light 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”, it is exactly the opposite: 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.
What are climate zones?
“In the morning it is changing to very cloudy with showers. In the afternoon the sun shows up at temperatures between 16 and 22 degrees ”, this is perhaps the weather report for southern Germany. The forecast is interesting for us because the weather is constantly changing. The situation is different with the climate, because that remains. Climate is the average weather in a region over a longer period of time. For example, the climate at the equator is hot and humid all year round. At the North Pole, on the other hand, the temperatures are icy and there is little precipitation. Between the equator and the poles there are again areas where, like us, things can be very changeable. But why is it that the climate on earth is so different?
The sun's radiation is not equally strong all over the world. How intensely it warms the earth depends on the angle of the sun's rays and thus on the latitude. Because the sun near the equator is almost vertical all year round, the earth is very heated here. In the direction of the poles, the rays of the sun hit at an ever flatter angle: the same solar energy is distributed over an ever larger area. Therefore, the greater the distance from the equator, the cooler it becomes. This creates regions with different climates, the climatic zones.
According to the strength of the solar radiation, four different climate zones can be divided on the mainland of the earth: The tropics around the equator, the subtropics (from the Latin word “sub” for “under”) between the 23rd and 40th parallel, the temperate Zone of our latitudes and the polar regions around the north and south poles. Like belts, they draw these climatic zones around the earth in an east-west direction.
The climate does not only depend on the latitude, other influences also play a role. There is snow on Kilimanjaro, even though it is in the tropics. The fact that its summit is icy is due to the fact that the temperature drops with increasing altitude. The mountain climate is therefore always cooler than lower lying areas.
The distance to the sea also has an impact on the climate: water can store solar heat longer than the mainland. It is also warming up more slowly than the country. As a result, the sea water acts as a buffer for temperatures. The climate is therefore mild near the coast. In the interior of the country, this heat balance is missing and the climate is continental, with temperatures fluctuating much more than in the maritime climate near the sea.
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 most of the time it also snows. 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 the process.
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.
The greenhouse effect
In a greenhouse, vegetables or flowers can thrive even when it's cold outside. That's because greenhouses are built out of glass. The glass - or a transparent film - allows the short-wave rays of the sun to enter the interior unhindered: the air warms up. On the other hand, the glass is impermeable to long-wave heat radiation, so the heat can no longer get out. That’s why it’s cozy and warm in a greenhouse.
Something similar is happening on a large scale on earth. The greenhouse gases carbon dioxide (CO2) and water vapor are naturally present in the atmosphere. Water vapor enters the air through evaporation, carbon dioxide through the exhalation. Volcanic eruptions also contribute to the natural carbon dioxide content of the air. Both gases have the same effect as the glass in a greenhouse: They allow the short-wave rays of the sun to penetrate to the earth. At the same time, like an invisible barrier, they hinder the long-wave thermal radiation on its way back into space. The heat builds up and the atmosphere heats up.
Without this natural greenhouse effect, life on earth would hardly be possible, because it would be far too cold for most living things. Instead of the current average temperature of plus 15 degrees, it would be an icy minus 18 degrees Celsius. The surface of the earth would be frozen!
The problem starts when we increase the amount of greenhouse gases in the atmosphere. This is mainly done by burning oil, natural gas and coal. Heating the apartment, driving a car, burning rubbish: all of these processes emit carbon dioxide. This CO2 has the largest share in the man-made greenhouse effect. But the cultivation of rice or cattle farming also intensify the effect: large amounts of methane (CH4) - also a greenhouse gas. In addition, nitrous oxide, ozone and fluorocarbons are among the greenhouse gases. Because all these gases slow down the heat radiation of the earth, the temperatures on our globe continue to rise.
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