Changes

[[Category: Physics]]

[[Category: Physics]]

The 4-space has to be flat since parallel transport of 4-vectors along its geodesic lines can't change the angles of those vectors for the reason of conservation of energy (the 4-vectors have to come back after the transport being directd in the same direction as before the transport since some of their components as energy or momentum in various directions must be conserved (by [[Loether theorem]]).

The 4-space has to be flat since parallel transport of 4-vectors along its geodesic lines can't change the angles of those vectors for the reason of conservation of energy (the 4-vectors have to come back after the transport being directd in the same direction as before the transport since some of their components as energy or momentum in various directions must be conserved (by [[Noether theorem]]).

   

   

That's why it is often important to be aware of various subtleties of names used in physics not to violate suddenly the conservation of energy and/or momentum, since so far the nature does not know how to make energy or momentum from nothing.

That's why it is often important to be aware of various subtleties of names used in physics not to violate suddenly the conservation of energy and/or momentum, since so far the nature does not know how to make energy or momentum from nothing.