Doom and gloom in Stuttgart

A total solar eclipse is not something you experience every day. The people of Stuttgart were all the more disappointed when a thick cloud cover blocked their view of the black sun. And instead of sunglasses, umbrellas were unpacked, because at the time of the eclipse, heavy rain was pelting down. The event lasted only two and a half minutes. The sky darkened and truly created an atmosphere of doom. And what probably annoyed the people of Stuttgart the most: At the decisive moment, a hole opened up in the cloud cover over their eternal local rivals Karlsruhe, of all places, revealing a view of the darkened sun.

The last total solar eclipse was seen in Germany in 1887, and the spectacle will not be repeated until 2081. Thus, the media had announced the rare event as a spectacle long in advance and reported live many times – if there was anything to see.

The moon’s umbra first hit the earth’s surface east of New York. In a few hours, it then travelled 14,000 kilometres across Europe to India, where it disappeared from the Earth’s surface again in the Bay of Bengal. Europe’s neighbours were also disappointed by the eclipse of the century due to bad weather. Only in countries like Iran or India was there a clear view the whole time and there were big celebrations.

Box seat above the clouds

Rich Americans and Britons paid over 4600 € to get one of the coveted seats in the supersonic plane “Concorde”. While on the ground most people in Europe were annoyed by the cloudy sky, the Concorde overcame all obstacles: it simply flew behind the shadow of the moon, offering the occupants a view of the darkened sun for almost six hours. Nevertheless, there were complaints: Some passengers had no clear view of the eclipse due to the crowding at the window seats – and demanded their money back.

How do solar and lunar eclipses occur?

In the past, when the sun or moon went dark, people feared the worst: misfortunes, disasters or even the end of the world. Today we laugh about this superstition. Nevertheless, a solar or lunar eclipse is an impressive experience. But how does it happen?

We know: The moon orbits the earth. When it moves exactly between the earth and the sun, it casts a shadow on the earth. From our point of view, it then covers the sun during this short time and it becomes almost as dark as night – although it is actually daytime. A solar eclipse has occurred.

In the case of a lunar eclipse, it is the other way round: the moon is then exactly behind the earth as seen from the sun – which casts a shadow on the moon. For us, the moon is then only faintly visible, usually in a reddish or brown colour.

But why are solar and lunar eclipses such rare events? Shouldn’t there be a lunar eclipse every time there is a full moon and, conversely, a solar eclipse every time there is a new moon?

No, because at full or new moon the three celestial bodies are almost never lined up exactly in a row. The reason for this is that the moon’s orbit is slightly tilted in relation to the earth’s orbit. The moon is therefore usually a little higher or lower than the sun and the earth. Then the sun’s rays have a clear path, the moon’s shadow passes the earth or the moon flies past the earth’s shadow.

Only very rarely is the moon in exactly the right place at exactly the right height, so that the sun, earth and moon are lined up and the moon’s shadow falls on the earth – or the earth’s shadow on the moon.

And even when an eclipse occurs, it is only visible for a few minutes, and not even everywhere on Earth. This is because the Moon is much smaller than the Earth and casts only a small shadow on the globe. And since the moon is constantly in motion, its shadow quickly moves on and the spectacle is quickly over. A lunar eclipse lasts a little longer. Because the moon is smaller than the earth, it is completely covered by the earth’s shadow and also takes longer to come out again.

How do clouds form?

How clouds are formed can be observed particularly well on cold winter days: When you exhale, steam comes out of your mouth – a whitish haze hangs in the air. It forms when the moist, warm air we breathe meets colder air. This is because warm air can store a lot of moisture – significantly more than cold air. When the warm air cools down, it can no longer absorb as much water. The excess water then collects to form small water droplets that float in the air and become visible as a white veil. It is quite similar with the “real” clouds.

The power of the sun heats the land and the water on the surface. The heat turns some of the liquid water into gaseous water: it evaporates. Because warm air is lighter than cold air, it rises. If the moist warm air cools down more and more towards the top, the excess water collects as droplets around tiny particles of dust or soot. This is also called water condensation. The droplets are still so small and light that they float in the air. A cloud has formed.

Clouds therefore always form when warm air cools down. This can happen when the ground and the air above it warms up and rises. Also, when the wind drives the air up a mountain range, warmer air is forced upwards. At altitude, it cools down and clouds form. The same happens when a zone of warm air meets a zone of cold air. The cold air causes the lighter warm air to rise and clouds form again!

But it does not rain immediately from every cloud. Only when the water droplets combine into larger drops due to air movement and are heavy enough, do they fall back to earth as rain. If the temperature is below 0° Celsius, the drops freeze into ice crystals. The precipitation then falls as snow, or in the case of thunderclouds as small graupel or large hailstones.

There are also clouds that form directly above the earth’s surface. This often happens in autumn, when the air cools down more and more. The whole landscape then appears blurred white. If you can see less than a kilometre through this white haze, it is called fog.

Why can we also see the moon during the day?

The tasks are clearly distributed: The sun shines during the day and the moon at night. But that’s not true at all: the moon can sometimes also be seen during the day – what’s it doing there?

Day and night have a simple cause: the earth rotates. When our position on the earth is facing straight towards the sun, it is bright, i.e. day. Later, when the earth continues to rotate, our location moves to the side facing away from the sun. We see the sun set and it becomes dark.

The moon also rises and sets – for exactly the same reason: because the earth rotates. But in addition, the moon also moves: in the course of four weeks, it circles the earth once. For half of this time, its orbit is on the side of the Earth facing away from the Sun. From there, you can always see it when your own position is just turned away from the sun – or in short: when it is night. But two weeks later, the moon is on the side facing the sun. Then it is the other way round: you see it together with the sun during the day when your own position is facing the sun.

So the moon can be seen sometimes during the day and sometimes at night, even if it actually belongs to the night for us. But this is simply because the moon is the brightest light in the sky at night and is therefore much more noticeable.