A universal constant is generally one of those numbers that we assume is the same at any point in the universe. Important numbers such as pi, e, gravitation, the speed of light in a vaccuum, charge on an electron, value of human life (that last one is still under debate...).

I say we assume that these numbers are constant everywhere. Certainly bad things would happen if we walked into an area where pi=4.5 and our blood vessels all decided to expand to meet the new requirement for circle circumference. And if light came to a dead stop in a vaccuum somewhere, there would need to be a damn good explanation -- probably prohibative to continued sentience. And if human life ever became devalued, well, then we might just live on Earth as we know it today. And that would be tragic.

So, we continue blithly along, assuming universal constants and trusting to my physics professors teaching: "This is all assuming the laws of physics do not change over time... an unproven assumption."

Regarding the Vorpal Blade hater's writeup, the following should be pointed out about the value of pi: The constant pi refers to the ratio between certain geometric aspects of a circle in Euclidian space! But as we know, real space is noneuclidian. This is Bad News for any claims regarding the invariance of, say, the ratio of a blood vessel's cross section to its radius (assuming the radius controls the pressure in this manner). Since this cross-section lives in a noneuclidian geometry, it is subject to change according to the local curvature tensor (or even just curvature, if you just want to do this in 3 dimensions). In other words, it is not constant!

We may therefore conclude that standing near a black hole might not be such a Good Idea. In the past, I placed a few warning signs near them, but somehow they all vanished.

THOSE THINGS ARE DANGEROUS! YOU HAVE BEEN WARNED!