I would recommend starting with C. Its probably better to get a grip on procedural programming principals before starting object oriented programming. Then learn python, its very powerful and time-efficient.
I don't know what kind of physics calculations you guys are doing, but I think pythons virtual machine should be able to handle most (basic) things, especially since you'll save so much time with the vast amount of libraries available.
Also, do you want to learn to program, or do you want to learn computer science? As far as I'm concerned, they're pretty different.
It might be helpful to post your end goal. Do you want to get into website development? It could come in handy. For example, I use perl a lot to help me sort design specification document references, resources, do menial tasks, search for things, etc. And of course, you don't need to know any computer science to do this, well, with the exception of knowing regex.
But I personally feel like once you know C very well, you can easily learn any other programming language. So again, I'd recommend learning C, some object oriented programming (go with java, python, C++, it doesn't matter), learn a bit of functional programming, it really helps you get into the whole recursion lingo, like haskell or scheme (check out SICP), some basic algorithms and data structures, and looking into regex.
I don't know exactly how much you're looking to get into programming, of course, but I'd recommend learning a little bit of assembly too (unless you're satisfied with C's abstract definition of pointers), how to debug is crutial as well (even using a nice debugger like windbg in visual studio or gdb in netbeans won't satisfy you completely unless you know assembly, for C/C++)
I could probably go on forever- but I will stop here.
To recap. I recommend:
-Learn C, and how to debug. Get into the basics of assembly too.
-Learn big O notation
-Read about data structures
-Learn Scheme or Haskell, practice your recursion skills
-Learn object oriented programming
-Learn to use regex