But I have a question, has human understanding of physics changed over the years? Has anything thought to be irrevocable been adjusted?
That is the very strength of the scientific method - it never claims to have total and totally accurate knowledge of everything (like the JWs or other bible fundamentalists) - only of the best scientific proof of the time:
As late as approximately 1860-1900 A.D., the leading scientists (including the famous Lord Kelvin) believed that the sun was powered by gravitational contraction. Radioactive processes were only beginning to be understood at the late part of this time.
Kelvin's gravitational sun process would have provided sun's energy for only about 20 million years - far too short to account for Darwinian natural selection, which was also a new development of this time. Lord Kelvin was, however, so famous that his reputation pretty much made Darwin give up on his theories of the age of the earth (at one time he believed earth age was practically infinite).
The answer came from a better understanding of radiation early in the 20th century - Ernest Rutherford among the leaders. This eventually gave rise to modern understanding of the sun process and the age of the solar system.
Still, while the current understanding is of a far older and far longer-lasting sun than earlier science - the sun is still definately not infinite.