This week I thought I would try to be entertaining, to distract myself and others from what has happened in Ukraine. So to start with, how big is a bacterium? As you might guess, it depends on which one, but I bet you didn’t guess the biggest. According to a recent article in Science Magazine (doi: 10.1126/science.ada1620) a bacterium has been discovered that lives in Caribbean mangroves that, while it is a single cell, it is 2 cm long. You can see it (proposed name, Thiomargarita magnifica) with the naked eye.
More than that, think of the difference between prokaryotes (most bacteria and single-cell microbes) and eukaryotes (most everything else that is bigger). Prokaryotes have free-floating DNA while eukaryotes package their DNA nucleus and put various cell functions into separate vesicles and can move molecules between the vesicles. But this bacterium cell includes two membrane sacs, only one of which contains DNA. The other sac contains 73% of the total volume and seems to be filled with water. The genome was nearly three times bigger than those of most bacteria.
Now, from Chemistry World. You go to the Moon or Mars, and you need oxygen to breathe. Where do you get it from? One answer is electrolysis, so do you see any problems, assuming you have water and you have electricity? The answer is that it will be up to 11% less efficient. The reason is the lower gravity. If you try to electrolyse water at zero g, such as in the space station, we knew it was less efficient because the gas bubbles have no net force on them. The force arises through different densities generating a weight difference, and the lighter gas rises, but in zero g, there is no lighter gas – they might have different masses, but they all have no weight. So how do they know this effect will apply on Mars or the Moon? They carried out such experiments on board free-fall flights with the help of the European Space Agency. Of course, these free-fall experiments are somewhat brief as the pilot of the aircraft will have this desire not to fly into the Earth.
The reason the electrolysis is slower is because gas bubble desorption is hindered. Getting the gas off the electrodes occurs because there are density differences, and hence a force, but in zero gravity there is no such force. One possible solution being considered is a shaking electrolyser. Next thing we shall see is requests for funding to build different sorts of electrolysers. They have considered using them in centrifuges to construct models to compute what the lower gravity would do, but an alternative might be to have such a process operating within a centrifuge. It does not need to be a fast spinning centrifuge as all you are trying to do is to generate the equivalent of 1 g, Also, one suggestion is that people on Mars or the Moon might want to spend a reasonable fraction of their time inside one such large centrifuge, to help keep the bone density up.
The final oddity comes from Physics World. As you may be aware, according to Einstein’s relativity, time, or more specifically, clocks, run slower as the gravity increases. Apparently this was once tested by taking a clock up a mountain and comparing it with one kept at the base, and General Relativity was shown to predict the correct result. However, now we have improved clocks. Apparently the best atomic clocks are so stable they would be out by less than a second after running for the age of the universe. This precision is astonishing. In 2018 researchers at the US National Institute for Standards and Technology compared two such clocks and found their precision was about 1 part in ten to the power of eighteen. It permits a rather astonishing outcome: it is possible to detect the tiny frequency difference between the two clocks if one is a centimeter higher than the other one. This will permit “relativistic geodesy”, which could be used to more accurately measure the earth’s shape, and the nature of the interior, as variations in density outcrops would cause minute changes in gravitational potential. Needless to say, there is a catch: they may be very precise but they are not very robust. Taking them outside the lab leads to difficulties, like stopping.
Now they have done better – using strontium atoms, uncertainty to less that 1 part in ten to the power of twenty! They now claim they can test for quantum gravity. We shall see more in the not too distant future.