The invention of cell phones, modern space probes, and checkout scanners would all—according to Adam Becker in his book What Is Real?—have been impossible without discoveries in quantum physics made in the early twentieth century.
Quantum physics, he explains, has been hugely successful in the practical world; but to this day, physicists have not come up with a fully satisfying theory about why minuscule particles (and waves) behave as they do.
He notes that the popularity of various theories about quantum physics began to change due to advances, ironically, in cosmology. As it turns out, the largest thing we can study is believed to have been packed into an incredibly small space: at the time of the Big Bang.
Fittingly, the word quantum can do double duty in referencing the great and the tiny. Quantum is a Latin term related to the word quantity, referring to an assessment of how much. The physicist Max Planck took the Latin word and applied it to science, so now a reference to the smallest indivisible part of something is known as a quantum.
Yet look up quantum in a dictionary, and you’ll find definitions that don’t seem so minuscule, such as “spectacular,” “sudden and significant,” “bulk,” and even “large.”
Isn’t it quite the quantum leap to go from subatomic particles to big, spectacular bangs and leaps and such?
Ah, well, quantum physics is full of paradoxes.