A lot of computational heavy tasks for science were done in Fortran at least ten years ago (and I think still are). I was told that's mainly because Fortran has a good deal of libraries for just that, and it was widely taught in academia so this is a common ground between the older and newer generations.

I think it may be gradually superseded by Python, but I don't know if it is

It was designed from its very start to be used for numerical computing. So the language it built around it and it sort of excels in that use case.

This used to be the holy bible of numerical methods, if you want to see some sample code: https://s3.amazonaws.com/nrbook.com/book_F210.html