3.3. Conclusions on H₀

To summarize, relative distance methods favor a value h 0.6-0.7. Meanwhile the fundamental physics methods typically lead to h 0.4-0.7. Among fundamental physics approaches, there has been important recent progress in measuring h via the Sunyev-Zel'dovich effect and time delays between different images of gravitationally lensed quasars, although the uncertainties remain larger than via relative distance methods. For the rest of this review, we will adopt a value of h = 0.65 ± 0.08. This corresponds to t₀= 6.52 h^-1 Gyr = 10 ± 2 Gyr for _m = 1 - probably too low compared to the ages of the oldest globular clusters. But for _m = 0.2 and = 0, or alternatively for _m = 0.4 and = 0.6, t₀ = 13 ± 2 Gyr, in agreement with the globular cluster estimate of t₀. This is one of the several arguments for low _m, a non-zero cosmological constant, or both.