After recalling why dynamical adjustment mechanisms represent a particularly attractive possibility for solving the cosmological constant problem, we briefly discuss their intrinsic difficulties as summarized in Weinberg's no-go theorem. We then comment on some problems of the recently proposed `self-tuning' mechanism in 4+1 dimensions. Finally, we describe an alternative approach which uses the time-evolution of the universe to achieve a dynamical relaxation of the cosmological constant to zero.
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