Seismic magnitude scales indirectly and incompletely reflect the force of an earthquake, involve other factors, and are generally limited in some respect of magnitude, focal depth, or distance. The "moment magnitude scale" – Mw or M – developed by and , is based on an earthquake's "seismic moment", M, a measure of how much work an earthquake does in sliding one patch of rock past another patch of rock. Seismic moment is measured in Newton-meters (Nm or Nm) in the SI system of measurement, or dyne-centimeters (dyn-cm) in the older CGS system. In the simplest case the moment can be calculated knowing only
Orders of magnitude (length) (10 m or 1.1 billion light-years). At this scale, expansion of the universe becomes significant. Distance of these objects are derived from their measured redshifts, which depends on the cosmological models used. To help compare different orders of magnitude, this section lists distances starting at 100 Ym (10 m or 11 billion light years). At this scale, expansion of the universe becomes significant. Distance of these objects are derived from their measured redshifts, which depend on the cosmological models used. Distances longer than 100 Ym Orders of magnitude (length) The following are examples of orders of magnitude for different lengths.