If the universal constants change, we have far more to worry about than our measurements being inaccurate.
Also, we can view the past for many of these constants (gravity, for example) by looking in telescopes to places many millions or billions of light years away- and what we see reflects gravity and the speed of light being the same as it was then. Why would it change now? Occam's Razor applies.
>"we can view the past for many of these constants (gravity, for example) by looking in telescopes to places many millions or billions of light years away- and what we see reflects gravity and the speed of light being the same as it was then."
Isn't this circular? The concept of a light year (and the determination of how far you are looking into the past, etc) assumes a constant speed of light.
There are also phenomena such as the natural fission reactor at Oklo that demonstrates that the fine structure constant hasn’t changed over the past 2b years.
Part of the definition of this constant is c and pi. It is very hard to alter one constant without altering another.
It's circular-ish, but we also see alignment in observable cosmic phenomena that strongly suggest the constants hold (such as the periodicity of pulsars being related to how fast they are moving relative to us, which we can measure via redshift).
Actually, the determination of how far you are looking into the past depends on both the constant speed of light _and_ the accelerating metric expansion of space:
Also, we can view the past for many of these constants (gravity, for example) by looking in telescopes to places many millions or billions of light years away- and what we see reflects gravity and the speed of light being the same as it was then. Why would it change now? Occam's Razor applies.