The easiest move might be to NumPy, assuming it can express your computations in its methods because if you're reduced to doing math in Python you're hardly any better off.
If you're willing to pay the price for Ruby there are certainly other viable options that aren't C. Learning the minimum Haskell to do decently fast math wouldn't be that hard and would not involve to much of the "weird stuff", for instance.
Much of our code is not CPU bound, and the PI is something of a Ruby evangelist. If everyone jumps away from Ruby it will never improve.
That being said, I don't think Ruby will ever be the fastest language, but speeding things up is always a good goal.
The easiest move might be to NumPy, assuming it can express your computations in its methods because if you're reduced to doing math in Python you're hardly any better off.
If you're willing to pay the price for Ruby there are certainly other viable options that aren't C. Learning the minimum Haskell to do decently fast math wouldn't be that hard and would not involve to much of the "weird stuff", for instance.