4 ms·
Conservation of momentum is a much bigger deal than conservation of energy. We already know of situations in which energy isn't conserved (like the energy of a
by repsilat 11y ago
Conservation of momentum is a much bigger deal than conservation of energy. We already know of situations in which energy isn't conserved (like the energy of a photon decreasing when there is metric expansion where it is.)
Conservation of momentum is a consequence of the translational symmetry of physics via Noether's theorem, so that's what we'd need to give up to hope to see it broken.
- leni536 11y agoMuch like conservation of energy is a consequence of time translation symmetry. If you mix spatial and time coordinates through relativity theory you can see that these are strongly coupled. Your photon example works because there is no time translational symmetry in the case of metric expansion and it's a general relativity model. In general relativity there is no conservation of momentum either. It would be hard to even define since coordinate systems change from point to point. We can only say that the energy-momentum vector is going through parallel transport, which is like conservation in the local coordinate system.