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Cake day: June 22nd, 2024

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  • Looking at the ideal gas law, p·v =T (v is the specific volume, the inverse of the mass density), I’d say beside the pressure p, i.e. the weight of the atmosphere above a point, it’s at least the temperature T that is quite different between Earth and Venus. An other factor is the compressibility of the fluid; our air is quite compressible, the atmospheric pressure is quite low and the ideal gas law thus gives a good approximation.

    As an atmosphere consisting of multi-atomic fluids, on Venus mainly CO_2, in an over supercritical state is far beyond what can be considered to be an ideal gas (low pressure, single-atomic gas), there are several other factors to be taken into account. The van der Waals law or the Clausius law are usually models to choose when dealing with real gases. However, as mentioned, the atmosphere is in an over supercritical state, i.e. beyond the critical temperature and pressure, the fluids are not in gaseous state, thus an even more complex material model is needed, to describe its behaviour.

    But to give an idea of the effect: When you measure the pressure and the density of the water of an ocean in different depth, you’ll notice the pressure increases linearly with depth, while the mass density of the water remains almost constant. Its low compressibility is why water often is treated as an ‘incompressible’ fluid. Similarly, this may work in an over supercritical fluid, as it has some properties that are similar to gases and some, e.g. lower compressibility, that are more similar to liquids.



  • According to German media, the guy came from Saudi Arabia in 2006, but is “ex-muslim”, “anti islamic” and supporter of German far right party AfD, some years ago he tweeted that he will take “revenge” for the treatment of Saudis seeking asylum in Germany. Thus, it is concluded that his motives were not djihadist.

    Sources:

    https://www.tagesschau.de/inland/innenpolitik/magdeburg-faq-100.html (in German):

    The arrested man is known as an activist critical of Islam who describes himself as an ex-Muslim. In social media, on Islamophobic websites and in interviews, he recently levelled accusations against the German authorities. Among other things, he accused them of not doing enough to combat Islamism and feared the Islamisation of Germany.

    On the online service X, he expressed his sympathy for the AfD and dreamed of a joint project with the far-right party: an academy for ex-Muslims.

    After going public years ago with his support for Saudi women fleeing their home country, he later wrote on his website in English and Arabic: “My advice: don’t ask for asylum in Germany.” According to the Reuters news agency, an insider from Saudi Arabia said that Saudi Arabia had warned the German authorities about the attacker.

    https://www.mdr.de/nachrichten/sachsen-anhalt/magdeburg/magdeburg/liveticker-anschlag-weihnachtsmarkt-magdeburg-100.html (in German):

    More and more information is now known about the alleged perpetrator. According to MDR information, the man wrote around a year ago in a now deleted post on the platform “X” that the German state was persecuting refugees from Saudi Arabia in order to destroy their lives. He is said to have announced “imminent revenge”, the newspaper “Welt” reported on Friday.












  • As subways are usually intended for traveling short distances, the passengers have to get in and out fast. Thus, subways usually have doors in shorter distance from each other than e.g. in train trolleys, that are used on lines where the stations are in larger distance from each other than subway stations usually are. The trolleys of double decker trains have stairs close to the doors, thus the trolleys for subways would need to have equivalently more stairs. Subsequently, the space gained for passengers to sit or stand would be much less than e.g. for double decker trains.