Main-Sequence Turnoff Ages of the Oldest Globular Clusters Against the Time a Bounced Cosmology Allows

The oldest globular clusters are the sharpest local clock available for testing any cosmology that replaces an initial singularity with a bounce. Using published main-sequence turnoff ages for six well studied clusters and the Planck cosmic age of 13.787 billion years, this study computes the time left between cluster formation and the beginning of the current expansion for each system. The oldest system in the sample, M92, carries a turnoff age of 13.18 billion years, leaving a margin of 0.61 billion years. After a two-standard-deviation allowance for the age errors, the tightest system, M92, still leaves -0.29 billion years for the cluster to form after the expansion began. No cluster in the sample requires time before the bounce, and equally the bounce framework as currently stated supplies no separate, larger age budget that these data could confirm: the test constrains, but does not distinguish. The study is computed from published values, not measured.