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Published online by Cambridge University Press: 25 May 2016
The present kinematics of an unrelaxed system such as the Local Group can be used to investigate its dynamics on a cosmological time scale. In particular, the classical timing argument of Kahn & Woltjer may be extended to distant satellite galaxies of the Local Group whose distances and velocities are known with some accuracy. Including a correction for the fact that the Local Group was not always dynamically isolated, I derive a mass for the Group of about 1.6 x 1012M⊙ and an age of 1.0 to 1.2 x 1010 years.