I love apostates, believers in or, better yet, conceivers of a theory who turn against it. They restore my faith in science, because they show that scientists can overcome attachment to their own brainchildren, a feat that is essential for progress and cannot be taken for granted. Paul Steinhardt, Albert Einstein Professor in Science and Director of the Center for Theoretical Science at Princeton University (Is there more impressive title in academia?), is an apostate. I first interviewed him in the late 1980s while researching quasicrystals, a weird, quasi-periodic form of matter once thought to be entirely hypothetical. Steinhardt coined the term “quasicrystals” and was a major investigator of them. In subsequent years I talked to Steinhardt about cosmology and in particular inflation, an idea that he helped refine in the early 1980s. Inflation holds that immediately after the big bang, our universe underwent an almost unimaginably explosive, faster-than-light growth spurt. Lately, Steinhardt has been criticizing inflation and related ideas, notably multiverses, in unusually blunt terms. So I was delighted when he agreed to answer some questions.

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