As others have commented, what you really want to learn is /programming/, not a programming language. And if you go into a field with "computational" in its name, you'd better learn it good. In order to become a decent programmer, you generally have to be "fluent" in multiple languages, as different languages are good for different problem domains. And in order to be a good programmer, you have to be at least a decent computer scientist (that means you need to know at least all the stuff taught in a BS course in Comp Sci, in particular algorithms and data structures to get started)
The most useful languages if doing numerics are likely Python or Matlab (choose one), C++, and C or Fortran (choose one). You should not start with C[1] or Fortran, as starting with either one will make you learn bad programming habits. You should start with Python, as this has the best effort-to-outcome ratio, and even when knowing only Python, you can get quite far. But you should be aware that there are things which simply cannot be done with it, many of which are important in fields with "computational" in their name.
About scheme: While scheme and common lisp are undoubtedly very powerful programming languages, you need to be aware that about 95% of the stuff they are good at can be done just as well in python (and much cleaner), and that if you seriously try to use them, you will quickly learn that you have to re-invent every single wheel (unlike in Python) and that you will be the only one in your lab using those languages. If you have some time, learn a LISP dialect by applying it to some toy project. It is fun and will make you grow as a programmer. But those are not good languages for everyday use, and nothing to get started with.[1] (as most of C is a subset of C++, learning C is mostly a question of learning how the C++ constructs are actually implemented. Pure C itself is redundant.)Edit: Yes, C++ is a horrible abomination straight out of hell (it is also a good example how you can arrive at a horrible result by doing only perfectly reasonable decisions.). However, it is still by far the best language for many kinds of applications, in particular all applications which call for *both* a software design (i.e., large applications) and raw performance (you can 100% performance in C++ if you know what you are doing). Most big applications in Windows, including Windows itself, are written in C++. There are good reasons for that.