# A decision back in time

### A thermodynamic solution

Lightning follows the simplest route through the sky; the path of least (electrical) resistance. A river flows from inland to the coastline in a similar fashion, flowing where hydrodynamic friction is minimal. It costs less energy.

Maybe linear time flows in a similar fashion, following the easiest route, costing the least energy.

There is an argument that the arrow of time can only move in one direction due to the second law of thermodynamics which says that entropy must always increase or stay the same. Entropy is the degree of disorder; a measure of chaos.

This is to say, that given any process it’s always easier to attain a disordered state than an ordered one. For example, it’s easier to sprinkle sugar into a cup of tea and let it dissolve, than it is to crystallise the sugar back out of the tea and collect the sugar crystals and put them back into the sugar bowl.

What this means in relation to time travel is that time is uni-directional; it can only move in the forwards direction because moving backwards would mean a decrease in entropy and that’s thermodynamically speaking, illegal.

### An alternate history

I recently read a discussion on a forum which centered on a couple of members who expressed a wish to go back to their past and change it so that they could relive a new life. I made a comment that changing our past may cause the creation of a new timeline, or a new multiverse where an alternative version of ourself would indeed live a new life…but that the original version of us would still exist and not experience that ‘new’ life.

My comment was followed up with an insightful view on human nature, that “…we have a tendency to “make the same mistakes” over and over”.

When I read that, I wondered whether this is because of the “the past is the past and cannot be changed” nut which cannot be cracked, or whether it’s simply the easiest route to follow.

### “An easy route…”?

It’s easier to fall with gravity than it is to climb against it. It takes less energy; it’s the easiest path, or ‘decision’.

Why do we make a certain decision? We take factors into consideration, weigh them up and make a decision based on the information at hand.

Even though the decision itself may be difficult (or following through with it), the answer is essentially the ‘easiest’ path to follow because it’s the outcome after the factors have been weighed and measured. By definition, it’s the correct solution, simply because it’s the outcome of the decision making process, whether it’s been made with our head or with our heart.

The easiest route for one person may not be easy for someone else.

Here’s an example. What shape fits into a round hole? Circle, square or triangle?

There’s an expression that “you can’t fit a square peg into a round hole”. So we’d say a circle.

And this is what we teach our children. At the same time, they might find it easiest to hold the sides of a triangle or a star rather than a smooth circle, and wedge that into the hole. They choose the easiest solution for themselves.

Dr Cox said that time travel is like finding a teapot in orbit around Venus. There’s nothing in the laws of physics to prevent it, it’s just extremely unlikely.

This is sounding statistical!

On a statistical footing, Stephen Hawkins in his book The Grand Design puts forward the idea that on a physical and chemical basis, there is a pre-known outcome in every decision. Momentum, energy, pathways, velocities and reactions etc. of the atoms, molecules and neurons in our brain all follow a prescribed – and therefore predictable – course. Thus, every choice we make has an inevitable outcome. It’s already been made.

In reality, there are so many billions of factors and environments (i.e. variables in the ‘decision equation’) as well as the sheer multitude of combinations and permutations, that effectively a decision cannot be reasonably predicted – and so we lump them all up and call it “free will”.

But free will can be dealt with on a semi-statistical / empirical basis. For example, it’s more likely that a vegetarian will choose to eat a salad for dinner tonight than a roast chicken. The vegetarian has a free will, but we can predict his answer reasonably well.

But let’s say that the lettuce is teeming with disease-ridden caterpillars. The vegetarian wants to go back and inform his younger self to stay clear of the lettuce.

Would his going back in time, armed with this new information gleaned from hindsight (or foresight, in this case) alter the original decision and allow for a new history (and self) to be created?

How likely is it the vegetarian would choose the chicken? Or would he still go for the salad but try to pick out the caterpillars? After all, he is a vegetarian. (And please note, I’m not saying here that vegetarianism is a wrong decision).

In these posts about the importance of history (Part 1 | Part 2) I pointed out how knowledge of the past can significantly affect how we might choose to behave in the present.

Knowledge of the history can and does affect the present and the future. These states in time are not wholly independent from each other, they’re cross related…which can be difficult to describe in a linear model of time.

Likewise, the idea that knowledge of the future affects the past wouldn’t fit into the linear model well either. This misfit is the ontological paradox, yet it wouldn’t exist in a multidimensional model of time, such as could be afforded through a quantum description.

Quantum mechanics turns the linear model on its head. The set laws of classical physics don’t apply when it comes to quantum scales so it might not be the case that every particle is predictable. A quantum particle can exist simultaneously in two states, in two places and at two times, for example. It gives Schrodinger’s cat a fighting chance.

The ‘easiest’ solution, then, now operates on more dimensions than the linear time line. Predictability is thrown out of the window and into orbit around Venus with its friend, the teapot.

Free will triumphs. And time travel? It’s looking like it will open up the opportunity for alternate histories and futures which may well have already played out. The past need not be set, and the future need not be predefined as our destiny or fate.

The future is yours…so is your history! Go grab them!

Paul

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