Paragraph: (Wiki_articles-paragraphs-wikiAlbert Einstein-66.txt)
Sent 1: General relativity includes a dynamical spacetime, so it is difficult to see how to identify the conserved energy and momentum.
Sent 2: Noether's theorem allows these quantities to be determined from a Lagrangian with translation invariance, but general covariance makes translation invariance into something of a gauge symmetry.
Sent 3: The energy and momentum derived within general relativity by Noether's presecriptions do not make a real tensor for this reason.
Sent 4: Einstein argued that this is true for fundamental reasons, because the gravitational field could be made to vanish by a choice of coordinates.
Sent 5: He maintained that the non-covariant energy momentum pseudotensor was in fact the best description of the energy momentum distribution in a gravitational field.
Sent 6: This approach has been echoed by Lev Landau and Evgeny Lifshitz, and others, and has become standard.
Sent 7: The use of non-covariant objects like pseudotensors was heavily criticized in 1917 by Erwin Schrodinger and others.