Time Travel And Complexity

/ sciencereason ... Complexity (Chapter 2): Time Travel, Time's Arrow And Complexity
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TIME REVERSAL
Wouldn't you love to be able to travel in time? Authors through the ages have explored the tantalizing idea of being able to travel into the past or the future!
Believe it or not, we are time-traveling right now ... into the future, one instant after another! But the question is: Does time only travel in one direction at one rate?
If we watch Alabama Slim breaking the rack in a game of 8-ball, we can easily tell if time is running forward or backwards. The backwards sequence doesnt break any laws of physics, but the coming together of all of the right factors to make it happen is so improbable that we can use the words never happen and be absolutely right!
In striking contrast, when two protons scatter off of each other, time seems totally reversible. The backwards version looks just like the forward version. So why is this so different from playing pool? The answer is that the interaction between the protons is simple.
PRESENT
Lets take a close look at how we experience time. Have you ever really thought about the difference between future and past? The difference between will and memory? The difference between hope and regret?
You can narrow and focus your attention so that you observe that split-second of what is called the present. What you are focusing on and noticing is the future flying into the past. If you can remember it, it is no longer in the present! The present where everything happens seems to have no extent at all.
Something that happened one second ago is already in the past. And, this is true for a millionth or a millionth-millionth of a second. Likewise the future is as close to now as is the past.
Okay while the present is an instantaneous moment for complex objects like you and me, it can be a very different story for electrons and quarks. These particles are described by an equation called a wave-function, and when two particles interact, their wave-functions become entangled ... but for how long? When do they reestablish their individuality? A physicist would ask When does the wave-function collapse?
Heres an electron named Henry bumping into one of his brothers. We know that after the interaction, Henry will be in one of two places ... behind Door A or behind Door B Its possible that for an extended period of time our timesecondseven minutes our electron can effectively be in both places at once (Now you know why Einstein thought these guys were nuts!).
One way to think of this is that the electron has a flow of time that depends only on its next interaction. Present for the simple electron is an indefinite extensionit remains in the present until some new interaction causes it to change its wave-function. And once that happens time has moved forward.
It does not take an observation or a measurement by a person to cause the electron to jump into place A or place B any new interaction can be the causea light shining on it or an electric field turning on. Any new interaction can cause the electron to jump into place A or place B a light shining on it or an electric field turning on It does not take an observation or a measurement by a person (an enduring misconception).
The collapse of the quantum wave-function is the point where the universe moves forward where present becomes past ... and where more than one possibility becomes just one actuality.
And Time itself becomes irreversible when the collapse effect spreads to enough atoms and molecules that the backwards sequence becomes so improbable as to never happen.
The more complexity, the more improbable it is for time to be reversible!
THE LARGE
Now lets jump from the small to the large. Here's a musician playing a ragtime piece on a guitar. At this scale, quantum mechanics is totally unnecessary to describe the scene. His atoms and the atoms in the guitar may be dancing around on a scale equaling their size, but none of that has a noticeable effect on the musician or the music.
The musician has a reliable and continuous existence.
There is nothing reversible in this scene. And there is uniqueness. Unlike electrons that are interchangeable, musicians are not!
The probability of finding another musician, exactly like this one, somewhere else in the universe, is virtually zero. Also notice that the chance of this musician being able to travel backward in time is equally zero.
Since his atoms are dancing about, continuously interacting, causing multitudes of wave functions to collapse, irreversibly changing possibilities into realities.
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