In March 1955, about a month before his own death, Albert Einstein sent a letter to the family of his recently deceased friend Michele Besso. “Now he has departed from this strange world a little ahead of me,” he wrote. “That means nothing. People like us, who believe in physics, know that the distinction between past, present and future is only an illusion, however stubbornly persistent.”
I do not know whether Besso’s family was comforted by this claim, but most of those who have a solid grasp of the issues say that Einstein was right about the science. A debate going back at least to Heraclitus (535-475BCE), who said that the primary feature of the universe is that it is always changing, and Parmenides (who said that there is no such thing as change) appears to have been settled. Indeed in 1949, on the occasion of Einstein’s 70th birthday, Kurt Gödel presented him with a mathematical proof of the nonexistence of time. Nature, it appears, is governed by eternal laws that stand outside time.
Not so fast. Notable among those who disagree is Lee Smolin, from the Perimeter Institute for Theoretical Physics in Canada. Smolin is one of the bad boys of contemporary physics and cosmology; a generator of radical ideas and an iconoclast. In the mid 90s he proposed that black holes spawn baby universes. In the middle of the last decade he published a searing attack on string theory which, he said, had failed to create a single testable prediction. And in his 2013 bestseller, Time Reborn, he argued that time is real and nothing transcends it, not even the laws of nature. Such laws are, like everything else, features of the present, and can evolve.
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