Point your friend to an article in the Creation Research Soc. Quarterly.
Morton, G. R., Slusher, H. S., Bartman, R. C., and Barnes, T. G., (1983).
Comments on the Velocity of Light.
Creation Research Society Quarterly. 20:63-65.
Summary: This is a critique of Barry Setterfield's suggestion that the
speed of light had decreased. If his formulation of the changes were true,
then there should have been 417 days per year at the time of Christ and the
earth would have been melted when God created Adam due to the tremendous
heat generated by the extremely rapid radioactive decay during the creation
week.
It is usually good to point people to creationist material that criticizes
their wild ideas. They beleive creationists they don't believe
evolutionists. Tom Barns and Harold Slusher are well know creationists.
glenn
Foundation, Fall and Flood
Adam, Apes and Anthropology
http://www.flash.net/~mortongr/dmd.htm
Lots of information on creation/evolution