# Series and Parallel Universes

Carried to its logical conclusion string theory leads to a multiverse, or landscape, of independent universes. There are two ways of viewing the multiverse and its constituent universes. There is a series view and a parallel view. In the series view, the multiverse is one universe but we, in our little pocket universe, can only see a limited portion of the multiverse. The rest is so far away and is moving so fast that information (light) from those nether portions cannot ever reach us. This boundary between the observable and the unobservable is the horizon. Because we cannot get any information from beyond the horizon, whatever happens there is irrelevant to us. Events beyond the horizon can have no effect on our pocket universe.

The parallel view of the multiverse is more interesting. In that view there are many universes evolving simultaneously. At 10-35 seconds after the Big Bang “bubble” or parallel universes began to form because of slight variations. In the parallel or many-worlds view, each time there is more than one possibility, the universe splits, one for each possibility. Consider a leaf on a tree. The leaf can fall or it can remain on the tree. At that juncture the universe splits, one for the possibility that the leaf falls and one for the possibility that the leaf remains on the tree. At that instant both universes are identical except for the one leaf, but from that time forward each develops independently of the other. What is “now”’ to us lies in the pasts of innumerable future universes. Everything that can happen does happen. Perhaps not in “our” universe but in one of the future universes.

The parallel view of the multiverse is what science uses to rebut the need for a creator. With so many evolving universes at least one was destined to be suitable for life. But this view falls apart unless evidence is found for the multiverse. Right now it’s a conclusion to be drawn from M-Theory, which in turn is derived from string theory, neither of which can be proven.

It seems we have three possibilities. One, the multiverse exists and we are here simply due to the laws of probability. With so many parallel universes one of the 10500 and probably more were suitable for life. Two, it’s all just a fluke. Like the one bridge hand dealt out of six billion possible hands, we got lucky. Three, there is a creator or some sort of intelligent design behind this universe.

Neither of the first two possibilities is very fertile ground for further speculation. Only statisticians get excited over probability and if this was just a fluke then that’s all that need or can be said about why we’re here.

But if a creator or intelligent design is thrown in the mix all sorts of intriguing questions pop up. What form does the creator take? What was happening before the Big Bang? If time began at the Big Bang was there even a “before” to talk about?

# Down the Rabbit Hole

We are nearly at the limits of knowledge when it comes to the universe. The Big Bang Theory and quantum mechanics have done a more than passable job of explaining what we see. Looking ahead, a few tremors creep into our smugness, however. Scientists worry that we may have passed from the realm of testable laboratory science into an area where the equipment is not sophisticated enough to discern between competing theories. That was the problem faced by Gamow, Alpher and Herman in the 1940s with the CMB radiation theory. Technology may well advance to overcome this fear.

Another concern is apophenia. Apophenia is the perception that there are patterns and connections where none exist. In statistics this is called a false positive. Apophenia is a part of human nature. Our hunter-gatherer ancestors had to be attuned to discern predators lying in wait. If they thought they saw a lion crouching in the tall grass and were wrong, they got a scare. If they failed to see the real lion hiding, they became lunch. The cost of believing a false pattern was less than the cost of not believing a real pattern.

One of the strongest primal instincts is that of finding meaning in life. We’re afraid of the void and the certainty of death so we try to find meaning in our lives. Yet quantum mechanics suggests that this universe is nothing more than a quantum fluctuation, a random event. Such a conclusion is not reassuring in the least.

So science soldiers on, desperately trying to prove itself wrong. The search now focuses on what physicists call a Grand Unifying Theory, something that will reconcile quantum mechanics and general relativity. Quantum mechanics only works when gravity is ignored, such as when the other three forces in nature are so strong that gravity becomes irrelevant. On the other hand, general relativity only works on such a large scale that quantum effects can likewise be ignored. A Grand Unified Theory would smooth the kinks between the two.

As we rewind the Big Bang everything collapses inward. The limit of understanding is reached at what is called Planck time, after physicist Max Planck. This is 10-43 seconds after the big bang. The universe is only 10-35 meters across, about 100 billionths of a billionth of the size of a proton. At that size time and space have no meaning. This is called the Planck scale. Heisenberg’s uncertainty principle says that particles pop in and out of existence and can be hugely massive if their life is very short. General relativity says that enough mass compacted into a small enough space creates a black hole, an area where gravity is so strong that light can’t escape. Put these two theories together and one result is that, on the Planck scale, virtual black holes can exist.

Some physicists have jumped on this to create a new theory, string theory. String theory is fiendishly complex. Imagine a guitar string. The string is under tension and can produce different harmonics depending on how it is plucked and where. Imagine a tiny string on the Planck scale, but still under tension. Some are free at both ends while some join ends to form circles. Strings can interact. As strings move through time they trace out a sheet, if they are open, or a tube if they are closed. Each string vibrates just like the guitar string and the particular vibration mode determines the mass, spin and electric charge of a particle.

At first string theory seemed promising as a Grand Unified Theory. In the 1980s scientists discovered not one but five separate string theories, with no way to determine which one was the “right” theory. Shades of Big Bang vs. Steady State!  In addition, string theory requires 10 dimensions.Then in the 1990s more work led to the conclusion that instead of being five separate theories, there were five ways to look at a single theory. There is an underlying theory called M-Theory that explains all five separate string theories.

The creator of M-Theory, Edward Witten of Princeton University, never explained what the “M” stands for. Some have suggested “mystery”, “mystic”, “monster”, “matrix”, “mother” (as in mother of all theories), and “membrane”. The latter, membrane, seems to have stuck. In M-Theory there is another dimension, bringing the total to 11 (but who’s counting?). A general object under consideration in M-Theory can range from zero dimensions to a total of nine. A point is a zero-brane. A two dimensional object is a two-brane, or membrane and so on. In three dimensions the theory has to deal with solid objects with interconnecting holes, much like a ball of knotted rope has the rope strands with space (holes) between the strands.  Over six billion “knots” have been described by means of another theory called Knot Theory.

By the time we get to 10 or 11 dimensions the number of possible objects is almost infinite. However if we limit ourselves to four dimensions of space-time, like our own universe, the number becomes a more manageable 10500. Each of these four-dimensional objects has more dimensions on the Planck scale (just as ours) and a unique set of forces and laws on the macroscopic scale. The question naturally arises, what if our universe is one of those 10500 possible states?

In the past couple of decades thousands of papers have been written by extremely bright theoretical physicists. Yet M-Theory hasn’t been proven. Some argue that because of its complexity and the fact that it is non-unique, it can’t be proven and therefore isn’t science any more than Genesis is science.

It used to be so simple. The universe was all there is and we strived mightily to explain it. Now it seems that our universe could be just a “pocket” universe in a landscape that is called the multiverse. The multiverse proposes a vast number of parallel universes, each with its own physical laws and all unobservable to us. If we can never observe them, can they be said to exist? It’s like the question, if a tree falls in the forest and no one is around, is there a sound?

Never mind. Having come this far we can’t retreat now. We shall proceed forward and consider the implications of the multiverse and a creator. Fair warning, dear Alices: we are about to go down the rabbit hole.