  Numerous studies over the past 30 years have suggested there is a causal
connection between the motion of the Sun through the Galaxy and terrestrial
mass extinctions or climate change. Proposed mechanisms include comet impacts
(via perturbation of the Oort cloud), cosmic rays and supernovae, the effects
of which are modulated by the passage of the Sun through the Galactic midplane
or spiral arms. Supposed periodicities in the fossil record, impact cratering
dates or climate proxies over the Phanerozoic (past 545 Myr) are frequently
cited as evidence in support of these hypotheses. This remains a controversial
subject, with many refutations and replies having been published. Here I review
both the mechanisms and the evidence for and against the relevance of
astronomical phenomena to climate change and evolution. This necessarily
includes a critical assessment of time series analysis techniques and
hypothesis testing. Some of the studies have suffered from flaws in
methodology, in particular drawing incorrect conclusions based on ruling out a
null hypothesis. I conclude that there is little evidence for intrinsic
periodicities in biodiversity, impact cratering or climate on timescales of
tens to hundreds of Myr. Furthermore, Galactic midplane and spiral arm
crossings seem to have little or no impact on biological or climate variation
above background level. (truncated)
