The Fourth Copernican Revolution
Martin Rees: A challenge for 21st-century physics is to answer two questions. First, are there many “big bangs” rather than just one? Second — and this is even more interesting — if there are many, are they all governed by the same physics? If we’re in a multiverse, it would imply a fourth and grandest Copernican revolution; we’ve had the Copernican revolution itself, then the realization that there are billions of planetary systems in our galaxy; then that there are billions of galaxies in our observable universe. But now that’s not all. The entire panorama that astronomers can observe could be a tiny part of the aftermath of “our” big bang, which is itself just one bang among a perhaps infinite ensemble.