Why more than 3 dimensions in linear algebra? This might seem a silly question, but I was wondering why mathematicians came out with more than 3 dimensions when studying vector spaces, matrices, etc. I cannot visualise more than 3 dimensions, so I am not seeing the goal of having more than 3 dimensions. 
Except from the fact that the general rules of linear algebra can be applied mathematically to vectors spaces of higher dimensions, what is the practical purpose of having more than 3 dimensions?
Linear algebra is also the study of system of linear equations that can have more than 3 unknowns, is this maybe related?
 A: You might want to look at applied sciences. Weather forecast seems to be a nice example which shows how a rather easy question leads to high dimensional vector spaces.
Suppose you want to predict the temperature for tomorrow. Obviously you need to take today's temperature into account so you start with a function $$f:\mathbb R\rightarrow\mathbb R,~x\mapsto f(x),$$ where $x$ is the current temperature temperature and $f(x)$ your prediction. But there is more than just the current temperature you have to consider. The humidity is important as well, so you modify your function and get $$\tilde{f}:\mathbb R^2\rightarrow\mathbb R,~(x,y)\mapsto f(x,y),$$ where $y$ is the current humidity. Now, the barometric pressure is important as well, so you modify again and get $$\hat{f}:\mathbb R^3\rightarrow\mathbb R,~(x,y,z)\mapsto f(x,y,z),$$ where $z$ is the current barometric pressure. Already this function can't be visualized, as it takes a 4-dimensional coordinate system to graph it. When you now take into account, that there are many more factors to consider (e.g. wind speed, wind direction, amount of rainfall) you easily get a domain with 5,6,7 or more dimensions.
