Can Time Flow Backwards?

PD writes "Exoscience has a story about the possibility that in some regions of space, time can actually flow backwards. Eggs would unbreak, supernovae would unexplode into stars, and living things would grow younger. I wonder if it makes hair grow back."

Comments

Why 4 dimensions and not 7

[LinuxParanoid]

Before your head explodes, read the following explanation why the universe has 4 dimensions, not 7 or some other number.

--LP ;-)

Re:Why 4 dimensions and not 7

[LinuxParanoid]

If you actually read even the articles there summarizing the findings, you'd see that the author addresses your points. To wit:

1D and 2D basically aren't complex enough to have life and self-aware creatures that could observe the universe (i.e. why "we" couldn't be in 2D universe)

you can model two or more time dimensions via mathematics. 2 time dimensions makes motion unpredictable, unpredicatable; self-awareness requires some ability to predict from "past" results

Not bulletproof of course, but thought-provoking.

--LP

Why 4 dimensions and not 7

[LinuxParanoid]

Before your head explodes, read the following explanation why the universe has 4 dimensions, not 7 or some other number:

http://www.hep.upenn.edu/~max/dimensions.html

--LP ;-)

Re:How to answer this question

[Admiral Burrito]

Very easy: First, find out what time is. Second, make it go backwards.

This is something that I just haven't been able to make sense of. How can time go "backwards"? Isn't the whole concept of "backwards" relative to time?

That is, you'd need some concept of "time" outside of our time by which the flow of our time could be viewed as "backwards". Or would you?

Am I making any sense here?

Even if they did exist,

[Inoshiro]

paradox would preclude you ever entering. The border'd be like the lint trap of the universe.

Here's an example:
You fly towards the zone of reverse time. Upon crossing the border, you go "back" in time, and reverse your newtonian motion back over the line. Once in "forward" zone, you get normal newtonian mechanics pushing you back in, ad nausieum.

If you wanted to leave in the reverse zone, you'd have to be in it already (good luck!), and you'd have to be reversing along to your entry point. Otherwise, the flow of time would be in defience of itself :-) Since your entry would be reversed once you leave, you'd be trapped again.

So before you go boldy reversing where no one has reversed before, you have to understand that you're either in it or not, relatively speaking, as your frame of reference would preclude you ever jumping to an alternate time stream/zone. If you were born there, we seem reversed. Vice versa. And there's no way to pass messages or objects, so there'd technically be no way for things to escape. Perhaps black holes are partially pockets of antitime?
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Re:speaking of universe theories

[Aatish]

There is another theory which states that this has already happened!

Dude needs to drink more

[Anomalous Canard]

I see his point that future boundary conditions imply regions of space where the arrow of time appears reversed. But, he's wrong in suggesting that the fact that a future crunch with all of the matter in the universe condensed means a highly ordered state. Hawking states that it is a highly disordered state and differs from the initial conditions of the Universe whice were in a highly ordered state. It's all condense becuase the Universe is smaller. It's not all condensed in a corner of a largely empty Universe just as the initial state wasn't condensed in the corner of an empty universe.

Also the odds for a future crunch don't look too good with all the observed deviations from a flat univers falling on the side of an open universe.

In short, Dude needs to drink more. We did better as undergrads in philosophy after a bender.
Anomalous: inconsistent with or deviating from what is usual, normal, or expected

Re:Dude needs to drink more

[Anomalous Canard]

Thank you for the book reference. I will check it out.

But my argument was more than just an appeal to an authority. I accepted that reversed-timelike things might happen if the future state were highly ordered/tightly constrained. I explained that his example was flawaed. Now you tell me: Why should I expect a highly ordered Big Crunch?

Anomalous: inconsistent with or deviating from what is usual, normal, or expected

Future constraints? The devil is a pool shark!

[WiartonWilly]

Future constraints is a "given" which I don't easily accept. Atomic cowboys are going to coral the atoms into a 1m cube in five minutes? Sounds like work to me! Or maybe it's like the pool-table trick where all the balls return to the triangle. Who sets up the shot? The devil is a pool shark!

He defined the problem away

[re-geeked]

In a universe whose interactions respond to future conditions rather than past conditions, wouldn't the "future" conditions be experienced as the past?

The "cause" of gas diffusion in our time-forward universe is that at time 0 it was in some unlikely state (past boundary condition), and it migrated to a more likely state by time 1. In a time-reverse universe, the "cause" of gas un-diffusion would be that at time 1 it must be in some unlikely state (future boundary condition), so it will migrate there from some likely state at time 0.

But, being a time-reverse universe, the "cause" of the future condition will be an even-more-future condition, and so on, and so on. In such a universe, the "record" of time would be a record of future conditions. Since we define "past" time as time that we have experienced, i.e. that we have a record of, it seems to me that the time perception in a time-reversed universe would be precisely the same as our time-forward perception.

So, a universe where future conditions will "cause" natural phenomena IS a world where past conditions did "cause" natural phenomena.

Correct or crazy?