> Then, I can look at the difference between clocks that came direct and clocks that came the long way. If all the differences are the same, then I can say that

> Then, I can look at the difference between clocks that came direct and clocks that came the long way. If all the differences are the same, then I can say that going A-to-B-to-C has the same effect as going A-to-C-to-B or B-to-A-to-C or any other route. Doesn't that show isotropy? Again, no, because you can only measure around the full loop. Any clock you can compare has gone just as far east as it has gone west, just as far north as south, and just as far up as down. You can rule out some particular kinds of anisotropy, but there are possible patterns that just wouldn't show up.