Is it? One objections to the Copernican theory was that it predicted stellar parallax, and none was visible with instruments of that time. Once we did, the universe bloomed, as it was obvious it had to be much bigger then we thought, had ever even imagined.
Then, years later, red shift was discovered, and what were once thought of as spiral nebula, were not nebula at all, but galaxies. Some like, some unlike, our own.
And the petals opened yet further.
Going the other way, atoms were once their namesake, indivisible, the ultimate building blocks of this world we love and see. Then electrons and neutrons, and protons, were discovered. Atoms could now be sliced, smashed together, and blown apart. But then we found still more, what these protons and neutrons were made from, the quarks in their several odd and peculiar flavours. And to go still further, there are those who propose a model based on a vibrating string.
Another way to put it may be that the more we know, the more we know there is to know.

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