Tag Archives: barometer

The weather globe – or the Goethe glass

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Again and again I look for simple, interesting things. This time I was fascinated by a measuring device or rather “display device”, whose operating principle is extremely simple and yet very effective. In addition, from my point of view, it is also an eye-catcher – it is the so-called Goethe Barometer. The best-known form is probably the bulbous glass hanging on the wall with a beak, similar to a watering can, in which the water level indicates the air pressure. I found a slightly differently constructed version of this glass on the net…

A little about the history of this structure:

To a gentleman named Evangelista Toricelli (1608-1647), an Italian physicist and mathematician, we owe the knowledge and proof that the air pressure is subject to fluctuations. He built the first barometer named after him in 1643. In 1644 he developed the mercury thermometer.

A small compensation area in the indicator tube protects against overflow

Der deutsche Dichter Johann Wolfgang Göthe, beschäftigte sich auch mit den Naturwissenschaften. Er machte selbst viele naturwissenschaftliche Experimente und entwickelte später ein einfaches, aber wirkungsvolles Barometer auf den Grundlagen des Toricelli.

Die Funktionsweise:

The barometer shows air changes quickly and precisely. When the air pressure rises, the water column in the indicator pipe falls and when the air pressure falls, it rises. This is made possible by the air trapped in the glass. The volume of the air always remains the same at a constant temperature. If the external air pressure rises or falls, the trapped air is compressed or expanded via the water column. Since the water cannot be compressed, it is the ideal medium to make the pressure differences visible. The height of the water column thus indicates the air pressure. If the air pressure is high in good weather, the external pressure is higher than the pressure of the trapped air and the water column decreases as the trapped air is compressed. At low air pressure, it can expand and the level of the water column increases.

the height of the water level in the pipe indicates the air pressure

This short time-lapse video shows the change in the water level when the air pressure changes:

The storm glass – the weather forecast

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Some time has passed since the last blog entry. On the one hand, I put this down to a lot of work, both professionally and privately, so that a bit of the energy for blogging was missing. The last days is the beautiful weather to blame. I preferred to spend my time riding a motorcycle instead of sitting behind the PC … But I also got a little gimmick again.

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FritzRoy storm glass

A colleague told me about it and at a large Internet mail-order company, I quickly found it. It is a so-called “FritzRoy storm glass“.

A storm glass is known for a long time from the seafaring. There it was used to predict weather changes. The storm glass is a glass cylinder filled with two liquids and hermetically sealed. The fluids are usually camphor and alcohol in saturated form, which do not mix but form small crystals. The formation of these crystals is related to the weather change. For a long time it was believed that the crystals react to changes in air pressure. Recent research allegedly suggests that the crystals react to electromagnetic fields called sferics. These sferics are preferably formed in low pressure areas. Thus, the storm glass shows the approach of a low pressure area and thus the bad weather.

 

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Crystals as weather forecast

The table (from the CarloMilano user manual) shows the different crystal weather relationships.

Clear liquid The weather is sunny and clear
Flaky liquid It is cloudy. Precipitation is possible
Small flakes It is foggy or damp
Little stars A thunderstorm is coming up
Little stars on a beautiful winter day It will snow
Big flakes It is covered. Snow is possible
Many crystals on the ground There is frost
Crystals on the surface It is getting stormy