Time to check some really old math, again. More than a hundred years of well-proven science assume just a few things are perfectly constant; Newton’s gravitational constant and the velocity of light are on the short list. Our most treasured theories (think: everything since Einstein’s Relativity) are based on them.
These fundamental laws of physics have been called into question a number of times since, as have the theories based on them. Even Einstein revised his work based on observations in the universe that begged closer scrutiny, like Red Shift. These second glances, in turn, have also been called into question as scientists work towards a utopian grand unified theory of physics that, one day, will explain the questions our founding theories did not answer.
Most recently, particle experiments at CERN may challenge what we know about the “constant” velocity of light. CERN scientists are welcoming close scrutiny of this recent observation, which clocks neutrinos breaking the law. Here are some links to more on the subject.
A great 2005 Scientific American article discussed the same in “Inconstant Constants”
Finally, my personal favorite set of articles challenging well-held theories including the big bang, see Dr. Halton Arp’s website