Ask Brian Greene: What Happens to Past and Future Me?

bg bwBrian Greene continues the WSF Live Forum all month long. Each day, he’ll answer one of your questions for this ongoing series that delves into the fundamental nature of space, time, and reality as we may or may not know it.

Watch the Live Forum webcast and submit your own question here

If the past, present and future are equally real (as discussed in “The Illusion of Time” episode), what happens when we die—in this picture, would our consciousness still exist in some sense?
— Sam Braverman, via WSF site

A good metaphor to have in mind is the one we briefly describe in the program: think of a movie that’s preserved on a reel of celluloid. The reel consists of a series of still images, each representing one moment in time (ignore the complication that the light rays which created the image generally travelled different distances to reach the camera and so reflect different moments). When you run the film through a projector, the still images create the illusion of a dynamic unfolding on the screen. At any given moment while watching the film, earlier moments seem to have passed away, and future moments seem yet to be. But from the perspective of the reel of celluloid itself, all the film’s moments are on an equal footing—they are all equally real.

While the metaphor is far from perfect, it gives a good sense of what it means to say that past, present and future are equally real—it’s as if reality itself is a giant reel of celluloid, with each still image recording everything that happens at a given moment of time. An important distinction from the film metaphor is that in the laws of physics, there doesn’t appear to be a projector light that singles out moment after moment after moment to be the momentary now, to be more real than the others. Instead, all moments simply exist, with no sense of a moment only becoming real when ‘illuminated’ and then fading into darkness.

In this way of thinking, your life spans a certain section of reality’s film—it is a collection of moments that begin with your birth and end with your death. The moments of your life, as with all moments, exist—they don’t become real and then drift away. There are surely moments in the film of all reality in which you don’t appear (before your birth, after your death) but each of those moments in which you do appear is as real as any other—and always will be. Again, moments don’t fade away into the past.

When one of Einstein’s close friends died, Einstein consoled his widow by saying, “Now he has departed from this strange world a little ahead of me. That means nothing. We convinced physicists know that the distinction between past, present, and future is only an illusion, however persistent.” I think Einstein’s empathy segued into poetry here—dying surely does mean something as the deceased is not part of subsequent moments—but the notion that the past is on the same footing as present and future (in the sense of not being gone), can certainly be consoling.

[Ed note: A previous version of this article published earlier today was missing the final paragraph above; we apologize for the oversight. Updated: Dec 1, 2011, 4:55 PM ET]

[Ed note: Brian Greene responds to feedback and clarifies his views on consciousness after death. Read it HERE Updated: Dec 2, 2011, 10:46 AM ET]

See other questions from this series

Brian Greene is co-founder of the World Science Festival and professor of physics and mathematics at Columbia University. His books include The Elegant Universe, The Fabric of the Cosmos, and The Hidden Reality. NOVA’s miniseries “The Fabric of the Cosmos” aired Wednesday nights all this month on PBS. You can watch all four episodes on the NOVA website.


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