Planet Grok

Where intuition reigns supreme

What is Time?

Posted by PlanetGrok on March 4, 2010

When I was a kid, I spent a lot of time thinking about these sorts of question that I was not fully equipped to think about. Nevertheless, many of my thought experiments were not too far from the truth. As a child, I thought that Time was an illusion created by entropy (I called it ‘movement’ back then), because I thought that if every last subatomic particle in my body froze in place, then I would not age- I would be literally “frozen in time”. This cool interview with Sean Carroll brings back memories of my childhood speculations. Apparently, my prepubescent grokkian senses were wrong and physicists have decided that time takes place even in completely empty space, which I am in no position to argue with.

Sean Carroll also mentions in this interview that time travel backwards is impossible, which I don’t think is entirely accurate – time traveling backwards in our own multiverse “strand” is probably impossible according to what I’ve read, but if it were ever possible to jump back into other (extremely similar) strands of the multiverse, then we would in effect be traveling backwards in time and we wouldn’t run into prohibitive Grandfather paradoxes.

They also have some discussion on how a high entropy universe such as ours came to be. Aesthetically, I prefer the idea of a big bang / big crunch cycle, but I think that hypothesis has been falling out of favor recently, probably to be superceded by Carroll’s model (described in the article) or something similar.

Further on in the interview, we read about what sounds like some fun, far-out postdoc work:

In fact, I have a postdoc at Caltech who’s very interested in the possibility of universes bumping into each other. Now, we call them universes. But really, to be honest, they are regions of space with different local conditions. It’s not like they’re metaphysically distinct from each other. They’re just far away. It’s possible that you could imagine universes bumping into each other and leaving traces, observable effects. It’s also possible that that’s not going to happen. That if they’re there, there’s not going to be any sign of them there. If that’s true, the only way this picture makes sense is if you think of the multiverse not as a theory, but as a prediction of a theory.
I, for one,want to bump into a multiverse with vastly different local conditions than our own. I hope we get absorbed right into it.
As a parting note, this interview also reminded me that I forgot to point out to OneSTDV a nice exception to his Law of Black Intellectualism.

8 Responses to “What is Time?”

  1. Vincent Ignatius said

    Take time as the fourth dimension and define a 4-velocity in four dimensions, analogous to 3D velocity. If the magnitude of that velocity is always constant (constant 4-speed), special relativity pops out. You can’t move faster through 3D space without going slower in time (to an outside observer).

    Cosmology is the most beautiful thing I have ever encountered.

    • PlanetGrok said

      Vincent, I don’t think I have the physics vocabulary on the tip of my toungue to adequately discuss this with you, but I’m going to try anyway.

      Using the definition in your explanation, and taking the example of my little thought experiment (where all the subatomic molecules in my body froze in place) although I would not chemically age, I would actually be hurtling through time faster than ever, because 3 D movement hinders the flow of time, as you say. Somewhat analogous to how a drowning animal in a river, flailing about, would cause the current(time) to push them downstream a little bit slower than a motionless log?

      Cosmology is beautiful. It would be a hell of a lot more beautiful if they could figure more o’this shit out. I often fantasize that our entire universe is just a subatomic particle in a larger universe, which is just a subatomic particle in a larger one, ad infinitum. Maybe our future intelligences, post-Singularity, will discover how to create a tailor made universe from subatomic particles. That’s something that could also explain the Fermi Paradox, lol. Raise your hand if you want to become a God!

      Are you a string theory skeptic, or do you think it is on the right track?

      • Vincent Ignatius said

        You would be going through time slower, but not much. Even going mach 10, the component of your 4-velocity that is moving through space is much smaller than the component moving through time. At 1/10 the speed of light, time would only be going about 0.5% slower for you. So slowing a molecule down from thermal velocities to nothing has very little effect on its speed through time.

        I don’t know enough string theory to be a skeptic or a supporter. The little bit I do know gives me hope that string theorists are on the right track. One of the problems is that the many string theories predict particles that we don’t have the technology to create yet. Oversimplifying, I can say theory A & B both predict everything we know about the universe now, but they also predict a bunch of different things we’re not sure about yet. To test those things requires a level of technology that we’re not even close to approaching.

      • PlanetGrok said

        Thanks for the insight.

        I hope on one hand that string theory is wrong because it seems so inelegant to me, and I doubt I’ll ever be able to grok 11 dimensions. On the other hand, if it is right then it would mean some of the great minds of physics haven’t been wasting decades of their energy chasing the wrong ball, which is a good thing.

        But my preferences all count for naught, of course, except on this lonely Planet.

  2. One Moniker said

    You’re a Vedantist!

  3. One Moniker said

    Forget reading the 4 Vedas. Just read Vedanta Sutra.

  4. […] What is Time? « Planet Grok […]

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