The longer you live with and apply Poincare's Riddle the more you can see how it's such a strong and powerful 'variable' with an enormous scope of applications.
Everything in your immediate proximity is growing! Everything in your field of view (except your field of view) is changing size by expanding. All particles, atoms, molecules, ponderable bodies and all spaces and forces betwixt are growing constantly and in perfect proportion; growing as if that were its very reason to exist.
To complete this simple image of the fourth dimension, you must only add your esteemed (if not estranged) self, your marvelous perceptions, your entire collection of measuring devices—don’t forget your clocks—and the millennia-old (though currently suppressed) mystery of weight.
Now, consider Henri Poincare’s “riddle”: If you were to wake up tomorrow and the universe and everything in it had doubled in size (as above), is there any way to tell? Is there any experience or experiment that could be performed to discover this phenomenon?
Sir Arthur Eddington gives us the common consensus: “Suppose that every length in the universe were doubled; nothing in our experience would be altered.” In other words, doubled compared to what? All standards of measurement and all forces have doubled also. Therefore, we’d never know about it. At least, so goes the standard conclusion which, as will be shown, is ipso-facto faulty. (see Opus III, "Poincare's Riddle")