All such attempts to show the supposed 'c-decay' have involved the researcher cherry-picking observations in support of his hypothesis. In at least one case I've seen, the researcher committed deep intellectual dishonesty and actually reported an erroneous datum specifically to make it agree with his hypothesis.
Modern physics does not support c-decay, nor any mechanism that might support it. There is no experimental evidence that shows it happens, and a great deal of theoretical work that shows it cannot.
"c-decay" is a theory that suggests the speed of light, denoted by the symbol "c", has been slowing down over time. This theory has been used by some to try to discredit the concept of an old universe and support the idea of a young earth. It is important to debunk this theory because it is not supported by scientific evidence and can lead to a misunderstanding of the age and origins of our universe.
The theory of "c-decay" was first proposed in the 1980s by a physicist named Barry Setterfield. He claimed to have found evidence of a decrease in the speed of light by comparing the measurements of the speed of light made in the 19th century to those made in the 20th century. However, his methods and conclusions have been heavily criticized by the scientific community.
There is overwhelming evidence from various fields of science, including astronomy, physics, and geology, that supports the constancy of the speed of light. For example, the observed behavior of light in distant galaxies and the precise measurements of the speed of light in different mediums all point to a constant speed. Additionally, there is no known physical mechanism that could cause the speed of light to decrease over time.
There are a few reasons why some people still believe in "c-decay". One reason is that the idea of a young earth is important to their religious beliefs, and they see "c-decay" as a way to reconcile the age of the earth with their beliefs. Another reason is that misinformation about the theory continues to circulate, leading to confusion and misunderstanding among the general public.
Debunking "c-decay" has no impact on our understanding of the age of the universe. The overwhelming evidence from a variety of scientific fields, such as astronomy, geology, and physics, supports the idea of an old universe. The speed of light is just one piece of evidence among many that confirms the age of the universe to be around 13.8 billion years old.