Nature is Exact!

In my first undergraduate year, I had to do a practical experiment involving a soap film stretched over a circular aperture. A small pressure difference across the film distorted it into a portion of a spherical surface, which could form an image of a needle placed at its centre of curvature. The quality of this image astonished me ??? it was as good as that of the best lens. I remarked on this ability of a simple bubble to form a surface correct to within a wavelength of light to my college tutor. "Ah!" he said, "you see, nature is exact." So, instead of giving my old job description as "establishing the SI as the basis of all measurement," which does not sound the most exciting task in the world, I could have said "finding out whether nature is indeed exact, and to what extent we can use its exactness," which sounds more interesting.