What makes you think physics can model everything? That's the point.
Math is FULL of functions that can be described -- have properties X and Y, which are useful to prove theorems -- which nobody has thought about how to compute.
(Obviously, there are the ones related to incomputibility like the Godel function, but there are others too... I'd appreciate help from others here :) )
And it might not even be useful or interesting (for the purposes of mathematics) to compute them. Not all math is constructive.
Likewise you can describe physical processes without computing them.
Math is FULL of functions that can be described -- have properties X and Y, which are useful to prove theorems -- which nobody has thought about how to compute.
(Obviously, there are the ones related to incomputibility like the Godel function, but there are others too... I'd appreciate help from others here :) )
And it might not even be useful or interesting (for the purposes of mathematics) to compute them. Not all math is constructive.
Likewise you can describe physical processes without computing them.