The main reason stuff stays in fortran is the general best practice of not messing with working shipped code. If the code needs regular work, for goodness sake use a maintainable language. But lots of fortran code has been stable for decades, and only a madman would go changing it.
No. The main reason we program in fortran is because the lirbary are known, have known error bars, known comportment , and are "provable". We *DO* reprogram every time we come up to a new problem which need to be translated. Chance is there is no standard code for what you want to simulate for your own specific problem. There are some rare case, like QM program (Gaussian, Molpro etc...) or some engineering program, but those are the exception not the rule.
That assumes that we know as much physics as they do. They might be using some medium to communicate that we haven't even discovered yet.
and you can assume pretty much anything whatsoever even instant wormhole stargate to ancient egyptian dude enslaving people. But within the scientific community this guy pretend to have consulted, we have a standard, and it is called what we have evidence for. As such, medium to communicate is light, and very slow compared to the interstellar distances, and distance to travel mind bogglingly vaste and nigh impossible to bridge with known physic. Etc....
IF I HAD A MINE SHAFT, I don't think I would just abandon it. There's got to be a better way. -- Jack Handley, The New Mexican, 1988.