# Should any theory of physics respect the principle of conservation of angular momentum or linear momentum?

Is it possible that a theory that can describe the universe at the planck scale can violate things that we now consider fundamental in nature?For example can it violate rotational and translational invariance and subsequently momentum wouldn't be conserved ?Should one consider these invariance principles to be fundamental that we must choose the lagrangian to respect them ?

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Conservation laws in theory are valid because they rest on solid and innumerable data. An experiment finding non-conservation of a law supported by theory would immediately invalidate the theory.

Our experimental experience is that the two laws you mention, conservation of angular momentum and momentum are such universal laws within the data we can access.

Theories are a different matter. Theories can be extended to variable and parameter regions where experiments cannot go at present or possibly ever. This does not necessarily mean that the extension of these theories will hold willy nilly in the unexplorable experimentally regions,( i.e. the conservation laws should also hold there experimentally). It is only necessary that at the limit where we know from the data that the conservation laws hold, the theories for the extended region reproduce the behavior of the standard theories, i.e. conserve these laws .

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