Funny timing. Yesterday I wrote about our use of time cliches. This morning I finally opened my latest issue of Scientific American. Yup, there’s a lead article about the asymmetry of time (runs only forward). It asks this question:
“The basic laws of physics work equally well forward or backward in time, yet we perceive time to move in one direction only—toward the future. Why?”
I’ve childishly puzzled over the philosophy of time since I was 12. None of the popular science nor most of technical books provide a decent explanation or answer to the above. You can find a huge amount of philosophy, math and physics that circle the question but never answer it. Why not?
Just like the cliches in my post yesterday, we lack the language. Time, as we experience and talk about it, moves only in one direction – forward – because time is relationship, a measurement of rate of change. It’s a lot like counting. No one ever asks why we can’t uncount. Counting goes in one direction, even if you are counting negative numbers. The number of counts always goes up. e.g. 1, 2, 3,4 = 4 counting events just as -1,-2,-3,-4 or 4,3,2,1 = 4 counting events. Measuring time is the same thing. Ticks. Even if you went “back in time” you’d still have ticks. That said, I think most people wonder why we can’t “undo” things. Why can’t I undo events in my life, unbreak the egg, unswirl the coffee – pick your metaphor. Even if you put it in complicated math and physics terms you never really get around to “going back in time”. You can return systems to previous states (likely not completely, but very close to initial states), but in doing so you’ll still have ticks that mark the transition to those previous states. Those ticks of time aren’t anything more than observational markers.
Ok. You still want to know why we remember the past but not the future? Again, another language trick. To remember the future all we need is to experience it. As soon as we experience it we’ll be able to remember it. Can we predict the future? No. And really we can’t “predict” the past (which is really what we do when we “remember”) like we try to do in anthropology, history, physics, etc. We can only model based on the accuracy of our data. We happen to have more data about the past so our “predictions” about what it must of been like with those set of conditions is slightly more accurate than what it will be like under conditions we’ve not yet observed. (try remembering when you were four. it’s probably about as accurate as what you think you’ll be at 84)
Sorry folks, there’s no shortcut and their may not even be a philosophical or physical paradox. Our limitations are related to language and metaphors.
I’m not suggesting I’ve unraveled the mystery of time or solved quantum physical problems. My claim is much more straightforward – the language and imagery gets in the way of what’s really going on.
Go back to the question at the top. It answers itself, in a sense. If the physical laws work “in either direction of time” and yet we perceive it going forward only. Our perceptions are a collection of observational ticks (we are always counting/adding to the number of observations, behaviors, memories, predictions, thoughts… go back to my point about time flies when you are having fun. The more you observe the more time (speed and volume) seems to pass.)
For those that want the good ol’ entropy discussion, read the SCIAM article.
This logic even works when talking spacetime and all that.
Again, it bears repeating, we have to be careful with the language. Time is a baggage word.
p.s. just for fun…
What about time travel? Is it possible? No. It basically asks can I reobserve/reexperience the same events or events I haven’t yet experienced. Doesn’t really make any sense. People get clever and suppose that it can happen and ask, “What if I met myself?” It wouldn’t matter.
You are different now than when you read this post. Your entire atomic structure is different. Why would it matter if you existing twice in one “instance of time” when you are never really you from one observational tick to the next? You can’t be duplicated in spacetime in exactly the same conditions and you certainly can’t be observed in exactly the same way in the same configuration.
Let me bring it home. Often people say well I can move backwards and forward in space, but not in time. That’s not really true of space either. Whether you move 1 meter forward or backwards the arrow of space was still going forward to 1 meter, a tick of distance.
“yeah, but I can return to a point in space! and I can’t return to a point in time!”
a) no you can’t go back to the exact point in space but I digress (points in space are relative to other points in space…)
b) time is the measure, in most use, of rate of change. It, too, is relative like space.
c) I have to think about framing this as a “closed system” question where we fix the frame of reference. Oddly enough, that’s not how we exist in the real universe. Nothing exists only in one frame of reference.
Time to go.
