The speed of light, gravity, electromagnetism and periodic elements are all changing. The speed of light for instance was thought to be faster at one time than it is today. It was once thought that nothing could travel faster than the speed of light, until recently research shows that subatomic particles like neutronis travel faster. Nothing about material nature is constant. The speed of light could change, gravity, EM could not work could cease to work, period elements could collapse etc.
Scientists very well know that in the practical world scientific laws are only approximation and real experimental data is not always as expected. There are various anomolies that take place even in testing basic ideas like gravity.
In quantum theory such constants like speed of light, gravity, electromagnetism, periodic elements seem to disappear altogether. Hence why physics applies two different theories to understand matter: GR and QM.