He falsely credits and idolizes Einstein, but probably has not read my book, How Einstein Ruined Physics.
In the module on "The Reality of Past, Present, and Future", he makes some faulty philosophical comments about time, that I recently attacked. After explaining some of the difficulty with relativistic simultaneity, he concludes:
So what this collectively tells us is that the traditional way we think about reality -- the present is real, the past is gone, the future is yet to be -- that is without any real basis in physics. What we are really learning from these ideas is that the past, the present, the future, are all equally real.So does relativity really require us to give up this basic intuition about time? I say no.
The essence of Greene's problem can be understood with pre-relativistic causality. Suppose I am on Earth, an alien is on another planet, and we somehow come to agreement about time. For me, "now" means that I can affect events in the immediate future, and likewise for the alien. But I cannot affect things in the immediate future on the other planet, because anything I cause on Earth will take some time to get to the other planet. So while the alien and I may agree about the meaning of "now" as it relates to our local clocks and our notion of local causality, it will still be the case that I can affect my environment before the alien can, and the alien can affect his before I can.
Relativity makes this more precise by saying that causality is limited by the speed of light, and by giving formulas for how motion can de-synchronize clocks.
The essential point is that the present now makes sense for me, and I can cause changes in the future, but only nearby, because there is no action-at-a-distance. Technically, I can affect my future light cone.
The alien might agree on what now means, and he can affect his future light cone, but my future light cone is different from his.
Thus Greene's conclusion above is entirely wrong. Our traditional notion of time, with its distinction between past, present, and future, does have a real basis in science. I explain this below in terms of time counterfactuals.
While Greene's explanation of relativity is mathematically correct, and his paradoxes might be confusing, the world would be more confusing without relativity. Suppose that my present now was dependent on the whole universe in the immediate past, and my actions affect the entire universe in the immediate future, without any time lag. That alien on another planet could do something to affect me a second later, and I could respond, to affect him in another second. That alien would never make sense of his world because some capricious intelligence in another galaxy could be interfering with his experiments. Relativity puts a lid on that, and ensures that local causes have only local effects.
Relativity gives us more reason to believe that we live in the present, not less. Time is more intuitive when causality has relativistic limits.