![]() It would also start off at a higher temperature, so the bacteria contained within would have a longer window of time within which to get munching. A human body is larger than a sandwich so will retain its heat for longer.Linking the idea to Blogstronomy's previous post about the fate of a person finding themself in space without a suit we could say the following: The discussions above hinge around the idea of a sandwich being thrown out of an airlock, but can be applied to any organic matter finding itself in space. Again, though, there will be a certain amount of heat stored in your ejected sandwich which means that our little friends have had yet another stay of execution. Space is cold, and bacteria require a certain amount of heat in order to work properly (from memory, I think most bacteria prefer temperatures of around 40 degrees centigrade, but there are 'extremophiles' that can work, and indeed thrive, at much higher and much lower temperatures). But wait- there's one other thing we haven't yet considered: It looks, then, like a sandwich in space would have a fair chance of at least starting to decompose- food, water, oxygen and the bacteria themselves are likely to be present in small quantities, so decomposition could theoretically start and then continue until one of these ingredients runs out. Again, though, there's a fair chance that there will be some oxygen hanging around in air pockets in whatever's to be broken down- there are plenty of such pockets in bread, for example. ![]() ![]() That means that this also would need to be supplied by the food that they're trying to decompose. There's no oxygen in space, at least not enough passing oxygen to be of any use to our bacteria. Space food, along with being irradiated (see above) is also often freeze-dried for the purposes of depriving bacteria of one of their raw materials. The good news (for them) is that most food items have a certain amount of water in them. There's no water in space, so if the bacteria are going to be able to break down your space-sandwich they'll need to get it from the food itself. Just as that sandwich is food for you, it's also food for the bacteria so there are no problems with this one. This probably won't happen straight away, though. However, there's a lot of radiation in space, so any food you throw out of an airlock will eventually have all of its bacteria killed off. Space food is irradiated in order to kill off as much of the bacteria as possible and therefore increase the lifetime of the food, but bacteria are hardy little things and it's nearly impossible to get rid of them all. If you throw a sandwich out into space it's unlikely to pick up any new passengers, but it's highly likely that there will already be a significant number of bacteria already starting to munch their way through your lunch. There are about 5 nonillion* bacteria on Earth and they are transferred to our food through the air or by touch. So if we were to, say, throw a sandwich out of an airlock, would it decompose? Lets look at all of the necessary ingredients for decomposition in turn: Some types of bacteria do not need oxygen (these are called anaerobic bacteria) but still require the other two ingredients. Most types of bacteria require three things to function: food, water and oxygen. When food decomposes, bacteria attack it and break it down into simpler substances. Since the number of terms in our decomposition (three) is equal to the number of nonzero, independent ways to contract an ACT down to the real numbers (three), we conclude that our decomposition is the orthogonal decomposition of the space of ACTs where the subrepresentations are inequivalent and irreducible.Question posed by and many thanks to for being my resident biomedical scientist. We conclude with a verification that the subspaces in our decomposition are in fact inequivalent and irreducible by applying another key result, Lemma 3.7, a representation theoretic tool used to sense irreducibility. We then count the number of nonzero, independent ways of contracting an ACT down to a real number and determine there are exactly three ways of doing so. This gives us a decomposition of the space of ACTs as the direct sum of three subspaces, which at this point may or may not be inequivalent or irreducible. First, we decompose the space of ACTs using two short exact sequences and a key result, Lemma 3.5, which allows us to express one vector space as the direct sum of the others. We decompose the space of algebraic curvature tensors (ACTs) on a finite dimensional, real inner product space under the action of the orthogonal group into three inequivalent and irreducible subspaces: the real numbers, the space of trace-free symmetric bilinear forms, and the space of Weyl tensors.
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