Certainty

...a red hot poker will burn you if you hold it too long; and...if you drink much from a bottle marked POISON, it is almost certain to disagree with you, sooner or later.[84]

In general, events in our universe seem predictable. But how predictable are they? Just because one event has always followed another in the past does this mean that it always will in future?

Philosophers call this the problem of 'induction'. How can I know that the rules that operate today, and have always operated in the past, will apply tomorrow? This is often illustrated by the turkey that is well fed and looked after so that for his whole life he knows that when the farmer comes it will be to feed him – until Christmas Eve.

As we can never test every present event, let alone future events, we can't be sure that things will behave the same way tomorrow. As a result we have realised that nothing can be absolutely certain. Instead we look for events that disprove a rule that we think might apply. We establish an 'hypothesis' (a rule we think might apply) and then attempt to disprove it. This is the essence of Logical Positivism, which I have already mentioned.

We know from astronomy and geology that the laws that govern the movement of planets stars, atoms, molecules and sub-atomic particles have been the same for a very long time. Our attempts to disprove them have either failed or caused us to find new laws that can't be disproved. As a result we expect these laws to be the same in the future.

If we knew enough about the laws of the Universe could we work out the future from the present?

Imagine we used a computer to model dice in a cup so you could see a picture of what was happening on the screen. We could then put into the computer just how two dice start in the cup and show what happens in the cup as it is shaken. If we know exactly how the cup is shaken we can work out how the dice will bounce and we could show exactly how the dice would fly out of the cup and hit the table, where they would stop and which face would be up when they stopped.

If we don't change the equations, every time we ran the computer program the result should be the same. In the same way, if we had a dice throwing machine that could exactly repeat its movements we would expect that the dice should end in exactly the same spot with the same numbers up every time. If they didn't we might assume that our machine was not exact enough or we had not eliminated some variation, like gusts of wind or dust on the table.

Manufacturers make this kind of assumption all the time. They know that they can reduce variability in their machines by improving their tolerances and accuracy and by demanding consistency in their materials. When all these are right they can get very close to the same result every time the machine runs.

We are pretty used to thinking we can predict things if we have enough information. People have been able to accurately predict eclipses of the sun and moon for many hundreds of years and we can now do it with accuracy measured in fractions of a second. Captain Cook came to map the East Coast of Australia because his expedition knew in advance that Venus would transit the sun at a particular time and that this would be seen from a particular part of the Pacific Ocean.

In the same way NASA can accurately calculate where a satellite will end up in space before they launch it. If it isn't quite right they assume that the rocket speed wasn't quite right or they didn't make the right adjustments for variations in atmosphere or gravity.

On a Universal scale, if everything is predictable then everything in the universe must have been pre-ordained from the beginning of time; the universe must be like a script written the instant it was formed. With the same starting conditions, it could be run like a video over and over, with exactly the same scenes repeated each time; one event inevitably following another; with only one, inevitable course. As time is one of its dimensions the universe is already complete and unchangeable.

Relativity made this possibility even more probable because to make observed relationships, like gravity, fit the equations time has to be a dimension like height, width and depth. Just as a distance exists between any two points; any two points are also connected by a time. Thus two times (or all times) must already exist in some way. Just as space has distance it has time.

We see only one instant on the time dimension (the present; the past is memory) so we are just turning the pages of our little chapter in time to see what happens next, because what we do and when we do it is already determined. And we do not have freewill. As Shakespeare wrote:

'All the world's a stage. And all the men and women merely players.'

To see the future, maybe all we need to do is build a huge computer (a big version of the ones weather forecasters use) and play the universe model forward to find out what will happen next; and I would write these words again and again and again every time the universe was replayed.

But what if events can go different directions from the same starting point; and there is a range of possible outcomes?