I’ve been interested in time and time travel for a very long time. Since I was a kid actually. Over the years there have been many different models of how this most fundamental aspect of the universe works. The most well known at the moment is the Multiverse Hypothesis.
The Multiverse Hypotheses suggests that every time there is a choice, right or left, blue door or red, meat or fish that the timeline divides and you have then two parallel universes that follow the result of those choices. It is an interesting idea, but finally after studying it for some years I came to the conclusion that it just doesn’t hold up. The trouble is that the Multiverse Hypothesis fails parsimony. It’s overly complex. Think about the millions of decisions people make. That would mean that there were millions of universes. But so many of our choices are irrelevant. Meat or fish? No difference in the big picture. Each decision would produce universes that are identical except that some person in a restaurant in Pris chose meat or fish. You could argue that only major decisions would split the time line, but who will determine what is an important enough choice to prompt a split into parallel universes and what is trivia? If all choices result in a new universe then you have chaos. Millions of nearly identical timelines except for one minute decision by some unimportant person that impacts nothing.
If you are talking about decisions and choices when did it start? Was there only one timeline until Australopithecus picked up a stick or a rock? Are there billions of universes where everything on Earth is absolutely identical but are the result of choices made by creatures living on alien worlds. How about choices made by animals, do they create timelines as well? Now we’d be up to trillions of universes, identical in every way except fido decided to scratch or sleep. And if every choice no matter how small prompts a split then even random events on the atomic scale would generate parallel universes. There would be a truly infinite number of universes, all identical except for one neutrino changing state in this way or that. The result would be worse than chaos.
The other issue I have with the Multiverse Hypothesis is that it would let you go back in time but not forward. You would have no way of knowing which future, of the trillions of trillions of universes are yours. You’d likely end up in one where everything was the same as where we are now but there would be two of you. That’s messy. This also violates Special Relativity. If you jump in a spacecraft and travel near the speed of light your frame of reference decouples from the rest of the universe. Your clock runs at a different rate from the rest of the universe. In a real sense you are travelling in time into the future. The question is what future? When you slow down and synch up with the frame rate of the rest of the universe is it your universe or one of the parallel ones. Possibly a parallel one where you did not get on the spacecraft and so you could encounter yourself. But this doesn’t happen. We would see evidence somewhere in all the particle accelerator experiments of a particle accelerated to nearly the speed of light disappearing, leaving our timeline. We have not seen that.
When you read material that uses the multiverse hypothesis often there is a very anthropocentric subtext. Only choices people make result in a new universe. This goes against the history of all we’ve discovered in science. Copernicus proved we aren’t in the centre of the universe. Darwin showed we evolved like all the other creatures on Earth. Hubble showed our sun was just one of millions in a Galaxy that was just one of millions in a Universe with no centre. It’s logical to conclude that we aren’t the focus of the timeline of the universe either. Yet, the Multiverse hypothesis seems to assume that the universe revolves around us. This implies to me that the Multiverse Hypothesis will end up in the scientific dust bin alongside Epicycles, and Alchemy and divine creation of people. Like flapping wing flight, medical humours, and the going around the earth, when people try to make reality fit the multiverse model, it falls apart.
The next question though is ‘if not the Multiverse Universe then what’?
Often if you say that you don’t believe in the multiverse hypothesis there is an assumption that you must believe in a deterministic universe. You must believe that there is one immutable timeline. That you were destined to be here at this time in this place. You had no choice and that all the universe is just a sequence of events running like a vast mechanical clockwork, determined by the state of all the atoms at the Big Bang. A butterfly flaps its wings in Japan to start a cascade of events so that three days later a hurricane hits Miami. The gears turn and every event pushes others around so that you can’t really change your fate. Christian Protestants are often fond of the deterministic model because it puts God in the centre of the universe. In their mind God has a plan for every person, tree, butterfly, and electron, and we cannot deviate from it. Even if we make a concerted effort to choose a different path, God planned that too. In their eyes, God even determined which people were unlucky enough to be caught up in Auschwitz or at their desks in the World Trade Centre and that he did so for his own reasons.
This makes God out to be the Universal Sadist.
In a physical sense though, like the multiverse, a purely deterministic universe also just does not work. It ignores that mechanical systems are sloppy. There is drag, odd things happen. A computer program is a set of instructions that behave mechanically. They should work without fail, yet have you never had a computer just do something ‘funny’? Have you never had a complex machine, such as a car just refuse to start, and then just as suddenly start working? Random events happen and these events violate the deterministic model.
Adam Sandler from Mythbusters tells a story of once when he was making a department store display. He had a device throw a baseball, it arched across the space, out of sight, into a net, and then rolled back behind the decorations to a hopper full of baseballs where it worked its way down and was eventually thrown again. He checked and tested and everything worked just as he planned. He knew the force and angle the ball would be thrown at and even used a much larger net to catch the baseballs than his calculations said he’d need as an extra safety margin. Everything said the system should just work. He turned the machine on, watched it running for a few minutes and it ran without fail so he left. When he got in the next morning, the hopper was empty and there were baseballs all over the floor. His system had not failed. No, it was just that once every 500 or 1000 throws the ball would just not end up where all the physics and engineering said it would. Weird things happen. Random events happen for their own reasons. The world is not deterministic.
A purely deterministic universe ignores that there are provably random events. You can’t know precisely when a particular particle will decay. You cannot know even with an infinite amount of data and computing power which straw will break the camel’s back. Some things just are random. Of course the very religious would argue that God does know and set precisely when the neutrino changes states or the bacterium dies. I’d argue that at the very least that would be a huge waste of His time.
The other thing a strictly deterministic universe does is to prevent time travel. If the universe has a single inflexible path it must follow then you cannot travel back in time. If you did then if you would invariably do something that would change the timeline, even if only to kill a bacterium and that’s not possible if the timeline is fixed. You also could not use Special Relativity to travel foreword in time, yet we know that happens. We’ve seen it. We even put an atomic clock in an airplane, flew it around the world and measured the slight difference between it and the earthbound clock. So no, like the multiverse, the deterministic, one path to rule them all, universe breaks down when you try to make the real world fit the theory.
In the end both the multiverse and the deterministic models become overly complex. The difference is that while the complexity is part of the universe in the multiverse hypothesis, it is just moved onto the God/nature/great spirit/whatever entity in a deterministic one. It doesn’t really solve the problem. It doesn’t answer the question. Also with both there is a significant lack of experimental or observational evidence to back them up. There has to be a third way.
So what is it?
In part two I will outline the Sloppy Universe. A model that does explain the universe, how it works, observations that support it, and why it allows for time travel.