The Past and the Future

What are the past and the future from a physicist’s viewpoint?

I don’t know – but have some thoughts over it. Here are my 5 cc.

Multiple Futures, Single Past

Most people believe that the future is open to changes. It seems obvious, after all, that it depends on whatever we do, and on our whims. If we step on a butterfly today, or spare it, our future may change drastically. It seems so obvious, so simple…

Some, however, think that everything is predetermined, and that we just don’t know it. It’s all cause and effect, they say. Like in Conway’s Game of Life, given a certain start, you will always have exactly the same development and end. Our freedom of choice is a fiction, born out of our ignorance. Could you be sure it’s not so?

Still others say that, yes, we have a freedom and may choose, but in end it all sums to the same. In a gas volume, the trajectory of every molecule is unpredictable, but the volume as a whole is subject to long-known, relatively simple laws. If we don’t kill this butterfly, it will die in a different way – and if it survives, another one will die instead. The end balances everything.

All the three positions seem to agree at one point: the future is generally unpredictable. If it is open to changes, then trying to predict it is senseless. If predetermined, but we don’t know what will follow… well, we don’t know what will follow. And if the end balances everything, we are far from finding this balance in advance.

As for the past, however, all seem to agree – it is fixed. Barring a time machine, it is immutable, the same forever. Obviously, nothing you can do now may change whatever is already done. There may be only one past, one truth about it. Anyone who will pretend otherwise must be either an ignorant fool, or a practical Orwellist.

Well, I manage to disagree with all these positions.

An effect of our perception?

We know, for example, that all possible colors of light can be received by mixing just three of them, the so-called basic colors – red, green and blue. Well, this is proven to not be true. It is us who actually perceive only three colors, and have to mix them to get all the others. We are misled into this three-colors belief by the peculiarities of our vision.

Similarly, we perceive the past as fixed and unchangeable, and the future as unknown and unpredictable, because our memory is far better than our prediction abilities. A person who has a bad memory, but is a good prophet, could believe the opposite – that the future is generally known, while the past is a terra incognita. Yes, this example doesn’t necessarily mean that we are wrong. But it shows us that this is possible. If our opinion about the past and the future is a result of the traits of our perception, then we could be wrong.

Actually, the physicists have long ago proven that we are.

The three views of the future

Since the discovery of the Heisenberg uncertainty principle, we know that the world is not deterministic. It is impossible to predict everything about a particle for any time ahead – we may only know it with a certain probability, within a probability distribution, subject to a deviation. Thus, we know that the second line of thought about the future, that it is predetermined but we don’t know it, is simply wrong.

There is still, however, the third line of thought. Yes, any specific particle may deviate, but the sum of them follows a predictable and simple way. In theory, or in the microscopic world, things are not predictable – but in reality, in the macroscopic world around us, everything is deterministic.

While this line of thought is true about a homogeneous system (eg. the said gas), it fails in heterogeneous ones. They tend to create focal points, where a little change may bring huge consequences. An everyday decision of an ordinary person is not going to have profound effect over the world, at least in the short run. But a decision of a world leader, taken in a key moment, could bring a nuclear Holocaust over the entire world – or to prevent one. And this decision differs from the opposite one just by the pattern of action of few tiny cells in the leader’s brain.

And what about the first line of thought, which states that the future is changeable to no end? Well, this is obviously not true, too. The stock market trends may be unpredictable, but what is the probability for a river to start flowing upwards? For the Moon to fall on our heads tomorrow, at 12:00:00 am? Should we expect eagerly for the world oceans to dry within an year, or for the mayors of New York and Moscow to decide to move these cities on each other’s place?… The physicists explain this again: such things are probable, but the probability is real close to zero. The larger the changes, the less probable they are.

The closeness of a future event has a key role to its predictability. The sooner it will happen, the less the opportunity for the uncertainty principle to show up. The farther it is, however, the more random and unpredictable events will stack to derail it from the road to the deterministic prognosis.

The immutable past

It may seem strange, counter-inuitive and even unbelievable – but the same is valid about the past. The reason is exactly the same – the uncertainty principle.

Trying to deduce a past situation from a current one meets the same problem as trying to predict a future one from the current state of the things. The longer ago that past have been, the more random and undeterministic events have occurred between it and now. They distort our recall, like multiple layers of bad window glass would distort our vision of the street outside. And since we have no way to know how each one of them does its distortion, and to what direction, we have no way to know what really happened.

Of course, we may have history records about this or that – but these records could be imperfect. What they represent as one king’s treachery could be a personal dislike for him, by the scribe or his master. What they explain as a coincidence of attacks could be a secret aliance, of which the witness didn’t knew. This name could be different, due to a mistake while copying the manuscript. That word may have meaned something different then – or almost the same, but with a very small, and sometimes very important difference… To cut the list short, the uncertainty principle shows here, too.

So, from a physicist’s viewpoint, the past is exactly like the future. The farther it is from now, the dimmer, the more uncertain it is. Of course, the things in even the most distant past have happened in exactly one specific way – exactly like in even the most distant future they will happen in exactly one specific way. It is that we have no way to know what this way was / will be. The uncertainty principle hides it.

The Future/Past Hourglass

Imagine the picture of two cones, touching their tops, like a hourglass. One of them is the past, the other one is the future. The point where they touch is the present time, the now of the world. It has a deviation of zero, and thus an infinitely small diameter. The farther from it, the larger the total uncertainty – that is, the diameter of the cone intersection.

The cones are not strictly delimited from the surrounding “nothing”. Given that the nature of the Heisenberg uncertainty is a probability standard deviation, the middle axis of the cone will be its thickest part. The farther we are from the cone axis, the thinner its “substance” is. Its density changes, following the Gaussian curve for the standard probability deviation. And the farther from the now we are, the thinner is the “substance” at any given point of the cone straight (perpendicular to the axis) intersection.

The focal point of the hourglass, the now, moves along them, following the axis of the cones – the time. For each point of this axis, the now has been, or will be there at some moment – thus, the entire “substance” of the cone will be concentrated there. So, to simplify the model, we may assume that every straight intersection of the cone contains the same “amount” of “substance”, no matter how far it is from the now.

In this model, the Heisenberg uncertainty, which depends on the Planck constant, is considered to be constant through the time, so the cones are completely symmetric. If the Planck constant is found to change with the time, the cones will be asymmetric – and their asymmetry could be interesting.

All this can be described in relatively simple equations. Not being physicist, I’m not sure when, and if I will ever do this. These equations may be important in understanding some things about the time.

And even more interesting is their metapart – the conversion and comparison of their operators. It could bring interesting ideas on what the time itself is actually made of, and in what way it participates into the making of some other elements of our existence.