Tufts/CfA/MIT Cosmology Seminar, at CfA: Tuesday, October 17, 1995 2:30 pm, Observatory Classroom A-101 Dr. Dimitar Sasselov Center for Astrophysics "Recent Results on the Primordial Helium Abundance and Big Bang Nucleosynthesis Consistency" Abstract: Current estimates of the primordial Helium-4 abundance may suffer from large systematic uncertainties (in the direction of being underestimated). Combined with recent results on D and Li, the value of Omega in baryons from Big Bang Nucleosynthesis (BBN) is reconsidered and the consistency of BBN examined. At a less significant level, the Helium-4 abundance also plays a role in constraining the lower limit on the age of the Universe (via globular cluster ages).