Barry Setterfield is not by any stretch of the imagination a mainstream scientist. He is a creationist astronomer who claims the speed of light has decayed and that this can be "proof" of a young earth.

from Wikipedia...(and if you object to this source there are a multitude of others)

Quote:
Creation science or scientific creationism is a branch of creationism that attempts to provide scientific support for the Genesis creation narrative in the Book of Genesis and disprove generally accepted scientific facts, theories and scientific paradigms about the history of the Earth, cosmology and biological evolution.

The overwhelming consensus of the scientific community is that creation science is a religious, not a scientific view, and that creation science does not qualify as science because it lacks empirical support, supplies no tentative hypotheses, and resolves to describe natural history in terms of scientifically untestable supernatural causes. Creation science has been characterized as a pseudo-scientific attempt to map the Bible into scientific facts.