Controversial theorist Aubrey de Grey insists that we are within reach of an engineered cure for aging. Are you prepared to live forever? On this glorious spring day in Cambridge, England, the heraldic flags are flying from the stone towers, and I feel like I could be in the 17th century—or, as I pop into the Eagle Pub to meet University of Cambridge longevity theorist Aubrey de Grey, the 1950s. It was in this pub, after all, that James Watson and Francis Crick met regularly for lunch while they were divining the structure of DNA and where, in February 1953,...